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The Family Myxococcaceae
Abstract
Myxococcaceae belong to the suborder Cystobacterineae in order Myxococcales and comprise three genera validly described as Myxococcus, Corallococcus, and Pyxidicoccus. Members of this family are widely distributed in soil and also occur in freshwater and marine environment. Myxococcus and Corallococcus appear to be the most commonly isolated myxobacterial genera in almost every soil sample. Myxococcaceae family covers the best explored and studied myxobacteria with a wide scope of research. The family’s pioneering and significant contributions to the order Myxococcales include (1) first genome to be sequenced, (2) discovery of first replicating plasmid, and (3) discovery of first bacteriophage. To date, several genomes are available belonging to Myxococcus and Corallococcus, and sequencing of Pyxidicoccus is ongoing. Albeit being common in the environment, metagenomics studies revealed that many members of this family still remain not cultivated. The important application of Myxococacceae family is reflected primarily on diverse secondary metabolites acting as antimicrobials, antiparasitics, antivirals, cytotoxins, and anti-blood coagulants. Bacteriocin-like activity and the potential application as biocontrol agent were also determined. Natural product discovery in this family appears promising as an important source of future drugs.
... In the ten described Corallococcus species with validated names, eight were primarily taxonomically described based on the draft genomic data [22]. The genus Corallococcus is known for its rippling swarm; hard, non-sporangiole-type fruiting body; and rounded myxospores [23], which makes morphology an important component in strain characterization. These combined growth features help distinguish this group of bacteria at the very early stage of strain isolation. ...
... Growth morphology characterization was performed on standard nutrient-lean media, including VY/2 and water agar baited with E. coli K-12, and in standard Casitonecontaining CY [23] and CY-H media. All solid media in this study contained 1.6% (w/v) Bacto agar. ...
... In contrast, the vegetative cells were non-motile, phase-dark, flexuous, and nearly spindle-shaped rods that measured 4.0-7.6 μm ( Figure 1h). All these growth stage characteristics fit within the genus Corallococcus [23]. Strain ZKHCc1 1396 T was catalase-positive, oxidase-negative, and stained Gram-negative. ...
A novel myxobacterial strain ZKHCc1 1396 T was isolated in 2017 from a soil sample collected along Chalus Road connecting Tehran and Mazandaran, Iran. It was a Gram-negative, rod-shaped bacterial strain that displayed the general features of Corallococcus, including gliding and fruiting body formation on agar and microbial lytic activity. Strain ZKHCc1 1396 T was characterized as an aerobic, mesophilic, and chemoheterotrophic bacterium resistant to many antibiotics. The major cellular fatty acids were branched-chain iso-C17:0 2-OH, iso-C15:0, iso-C17:1, and iso-C17:0. The strain showed the highest 16S rRNA gene sequence similarity to Corallococcus terminator CA054A T (99.67%) and C. praedator CA031B T (99.17%), and formed a novel branch both in the 16S rRNA gene sequence and phylogenomic tree. The genome size was 9,437,609 bp, with a DNA G + C content of 69.8 mol%. The strain had an average nucleotide identity (ANI) value lower than the species cutoff (95%), and with the digital DNA-DNA hybridization (dDDH) below the 70% threshold compared to the closest type strains. Secondary metabolite and biosynthetic gene cluster analyses revealed the strain's potential to produce novel compounds. Based on polyphasic taxonomic characterization, we propose that strain ZKHCc1 1396 T represents a novel species, Corallococcus soli sp. nov. (NCCB 100659 T = CIP 111634 T).
... Whether they are transient or truly originate from the sea, phylogenetic classifications allow one to determine if a given strain is a halotolerant or halophilic myxobacterium [11]. Strains belonging to the Cystobacterineae-type are predominantly non-halophilic except for halotolerant strains of Myxococcus xanthus, Myxococcus virescens, Myxococcus macrosporus [12], Myxococcus fulvus (strain HW-1) [13], Angiococcus, Corallococcus, and Cystobacter [9]. Isolated myxobacterial strains belonging to the suborder Nannocystineae are unique in that they grow in a wide range of salinity, and hence comprise the obligate halophilic genera Haliangium, Enhygromyxa, and Plesiocystis. ...
... On the other hand, the halotolerant and genome sequenced strain Myxococcus fulvus HW-1 [13] appears to be closely related to Myxococcus macrosporus based on 16S rRNA gene sequence phylogeny. So far, the culturally described halotolerant myxobacteria were only known in Nannocystineae and Cystobacterineae suborders [7,9,12]. However, obligate halophilic strains were exclusively found in Nannocystineae [5,6,8]. ...
Over the last two decades, halophilic (organisms that thrive at high salt concentrations) and halotolerant (organisms that have adapted to high salt concentrations) myxobacteria emerged as an important source of structurally diverse secondary metabolites from the marine environment. This review explores the advance of metagenomics analysis and 16S rRNA gene phylogeny of the cultured and uncultured myxobacteria from marine and other salt-environments up to July 2018. The diversity of novel groups of myxobacteria in these environments appears unprecedented, especially in the Sorangiineae and Nannocystineae suborders. The Sandaracinaceae related clade in the Sorangiineae suborder seems more widely distributed compared to the exclusively marine myxobacterial cluster. Some of the previously identified clones from metagenomic studies were found to be related to the Nannocystineae suborder. This understanding provides the foundation for a vital, unexplored resource. Understanding the conditions required to cultivate these yet “uncultured” myxobacteria in the laboratory, while a key next step, offers a significant potential to further expand access to diverse secondary metabolites.
... Samples were air dried in the laboratory and then inoculated onto culture medium. Standard isolation methods using WCX and STAN-21 agar (Garcia and Müller, 2014a,b) were employed for bacteriolytic and cellulolytic myxobacteria respectively. Molten WAT agar (0.1% w/v CaCl 2. 2H 2 O, 1.5% w/v agar, 20 mM HEPES) at 55 @BULLET C was supplemented with 2.5% cycloheximide to a final concentration of 25 mg/ml (WCX). ...
... A 1 ml volume of the washed cells was poured and spread onto a 14 cm diameter WAT agar plate and dried to form a uniform lawn. Myxobacterial isolates were grown in AMB broth (Garcia and Müller, 2014a,b) at 30 @BULLET C for 5–7 days to obtain a dense culture (OD 600 of ∼2). Cultures were then subjected to centrifugation at 4000 × g for 30 min, the pellet was washed in TM buffer and 10 µl of the cell pellet spotted onto the prey lawn. ...
Myxobacteria are natural predators of microorganisms and the subjects of concerted efforts to identify novel antimicrobial compounds. Myxobacterial predatory activity seems to require more than just the possession of specific antimicrobial metabolites. Thus a holistic approach to studying predation promises novel insights into antimicrobial action. Here, we report the isolation of 113 myxobacteria from samples of soil taken from a range of habitats in mid Wales. Predatory activity of each isolate was quantified against a panel of clinically important prey organisms, including Klebsiella pneumoniae, Proteus mirabilis, Candida albicans, Enterococcus faecalis, and three species of Staphylococcus. Myxobacterial isolates exhibited a wide range of predation activity profiles against the panel of prey. Efficient predation of all prey by isolates within the collection was observed, with K. pneumoniae and C. albicans proving particularly susceptible to myxobacterial predation. Notably efficient predators tended to be proficient at predating multiple prey organisms, suggesting they possess gene(s) encoding a broad range killing activity. However, predatory activity was not congruent with phylogeny, suggesting prey range is subject to relatively rapid specialization, potentially involving lateral gene transfer. The broad but patchy prey ranges observed for natural myxobacterial isolates also implies multiple (potentially overlapping) genetic determinants are responsible for dictating predatory activity.
... a Kulichevskaya et al. (2014). b Garcia and Müller (2014). c Qiu et al. (2014). ...
Invasive plants are a major problem for land managers and have widespread and lasting environmental impacts. The invasive shrub Amur honeysuckle (Lonicera maackii) is a pervasive and noxious plant in the Midwest region of the United States.
Despite this, many land managers may be uncomfortable with herbicide control of this and other invasive plants due to unknown impacts on ecosystem components including soils.
To examine if herbicide control of Amur honeysuckle impacts soil enzyme activity and soil communities, we treated Amur honeysuckle with Garlon® 4 (triclopyr) suspended in Basal Bark Oil, Basal Bark Oil alone and untreated controls, then assessed soil community, soil enzyme activity and arbuscular mycorrhizal density changes among treatments and across the subsequent growing season.
We found that basal bark herbicide treatments of Amur honeysuckle do not negatively impact soil enzyme activity, nor do they impact fungal, prokaryotic or oomycotan diversity or community structure. There was a slight but likely ecologically unimportant effect on community structure associated with basal bark oil applications, but not with herbicide applications. Arbuscular mycorrhizal colonization was negatively affected by herbicide use but this is likely due to reduction in host health and/or mortality.
Taken together, this suggests that herbicide control of Amur honeysuckle does not impact soils and land managers can treat these invasive plants without concern for negative soil outcomes.
... Mining of new microbial resources adapted to complicated soil environments and equipped with different biocontrol mechanisms is necessary for successful biocontrol of phytopathogens. Myxococcus and Corallococcus are among the most frequently isolated myxobacteria genera from soil [47]. Some Myxococcus strains have been evaluated as antimicrobial potentials, especially M. xanthus as model species of myxobacteria [48]. ...
The application and promotion of biological control agents are limited because of poor efficacy and unstable performance in the field. Screening microorganisms with high antagonistic activity, effective adaptability, and high field-survival should be prospected. Myxobacteria are soil predatory bacteria with wide adaptability, which are considered as good antagonists. Here, we report a myxobacterium strain M34 isolated from subtropical forest soil in South China using the Escherichia coli baiting method. Based on the morphological observation, physiological test, biochemical characteristics, 16S rRNA gene sequence, and genomic data, strain M34 was identified as a novel genus and novel species, representing a new clade of Myxococcaceae, for which the name Citreicoccus inhibens gen. nov. sp. nov. is proposed (type strain M34T = GDMCC 1.2275T = KCTC 82453T). The typical features of M34, including fruiting body formation and extracellular fibrillar interconnection, indicated by microscopic observations, contributed to cell adaption in different environments. Furthermore, the strain showed antifungal activity against phytopathogenic fungi and predatory activity to both Gram-negative and Gram-positive phytopathogenic bacteria. The bioprotective mechanisms are attributed to the presence of pyrrolnitrin and derivative with antifungal activity and the extracellular proteins with lytic activity against pathogenic bacteria. Due to its multiple beneficial traits, strain M34 has the potential to be developed into a versatile biocontrol agent for the management of both fungal and bacterial phytopathogens.
... The myxobacterial strain MSr12020 was recognized for its swarming and fruiting body formation in the standard Escherichia coli bacterial baiting method (Garcia & Müller, 2014). Repeated transfer of the swarm edge onto fresh-buffered VY/2 agar led to the isolation of this myxobacterium. ...
Sorangipyranone was isolated as a novel natural product featuring a unique 2,3-dihydro-γ-4H-pyrone scaffold from cultures of the myxobacterial strain MSr12020. We report here the full structure elucidation of sorangipyranone by spectroscopic techniques including 2D NMR and high-resolution mass spectrometry together with the analysis of the biosynthetic pathway. Determination of the absolute configuration was performed by TDDFT-ECD calculations and determination of the applicability of the Snatzke's helicity rule, to correlate the high-wavelength n→π* ECD transition and the absolute configuration of the 2,3-dihydro-4H-γ-pyrone, was done by the analysis of low-energy conformers and the Kohn-Sham orbitals. Sorangipyranone outlines a new class of a γ-dihydropyrone-containing natural product comprised of malonyl-CoA-derived building blocks and features a unique polyketide scaffold. In silico analysis of the genome sequence of the myxobacterial strain MSr12020 complemented with feeding experiments employing stable isotope-labeled precursors allowed the identification and annotation of a candidate biosynthetic gene cluster which encodes a modular polyketide synthase assembly line. A model for the biosynthetic pathway leading to the formation of the γ-dihydropyrone scaffold is presented in this study.
... The Syntrophobacteriaceae includes syntrophic and sulfate-reducing genera [48]. Myxococcales are aerobic and frequently encountered in soil [49]. The Geobacter are a group of strictly anaerobic or oxygen sensitive Fe(III) and Mn(III/IV) reducing bacteria [50]. ...
Coal mine spoil is widespread in US coal mining regions, and the potential long-term leaching of toxic metal(loid)s is a significant and underappreciated issue. This study aimed to determine the flux of contaminants from historic mine coal spoil at a field site located in Appalachian Ohio (USA) and link pore water composition and solid-phase composition to the weathering reaction stages within the soils. The overall mineralogical and microbial community composition indicates that despite very different soil formation pathways, soils developing on historic coal mine spoil and an undisturbed soil are currently dominated by similar mineral weathering reactions. Both soils contained pyrite coated with clays and secondary oxide minerals. However, mine spoil soil contained abundant residual coal, with abundant Fe- and Mn- (oxy)hydroxides. These secondary phases likely control and mitigate trace metal (Cu, Ni, and Zn) transport from the soils. While Mn was highly mobile in Mn-enriched soils, Fe and Al mobility may be more controlled by dissolved organic carbon dynamics than mineral abundance. There is also likely an underappreciated risk of Mn transport from coal mine spoil, and that mine spoil soils could become a major source of metals if local biogeochemical conditions change.
... In detail, Chitinophaga, Flavitalea, and Terrimonas in Chitinophagaceae, Nibribacter in Cytophagaceae, Gemmatimonas in Gemmatimonadaceae, Aggregicoccus, Angiococcus, and Corallococcus in Myxococcaceae, Oxalicibacterium in Oxalobacteraceae, and Singulisphaera and Blastopirellula in Planctomycetaceae may be important because they were only found in the d1 and d2 treatments of reestablished suppressive soils (Fig. 2d, e). Also, culturable strains were reported in these genera (Zhang et al., 2003;Schlesner et al., 2004;Sahin et al., 2010;Kulichevskaya et al., 2012;Kang et al., 2013;Garcia and Müller, 2014;Rosenberg, 2014;Sood et al., 2015;. ...
... Myxobacteria include broad prey range predators such as Myxococcus xanthus, Myxococcus flavescens, Myxococcus virescens, Myxococcus macrosporus, Corallococcus coralloides, Stigmatella aurantiaca, Chondromyces apiculatus and Chondromyces crocatus [44]. Compared with Bdellovibrio and BALOs, which exhibit a restricted prey spectrum, myxobacteria are able to kill a broad range of bacteria, including clinically relevant species [66][67][68][69][70][71][72][73][74][75][76][77][78]. This is probably due to their capacity to secrete a plethora of lytic metabolites which, acting either in isolation or synergistically, are able to attack a wide variety of prey. ...
Discovery of antimicrobials in the past century represented one of the most important advances in public health. Unfortunately, the massive use of these compounds in medicine and other human activities has promoted the selection of pathogens that are resistant to one or several antibiotics. The current antibiotic crisis is creating an urgent need for research into new biological weapons with the ability to kill these superbugs. Although a proper solution requires this problem to be addressed in a variety of ways, the use of bacterial predators is emerging as an excellent strategy, especially when used as whole cell therapeutic agents, as a source of new antimicrobial agents by awakening silent metabolic pathways in axenic cultures, or as biocontrol agents. Moreover, studies on their prey are uncovering mechanisms of resistance that can be shared by pathogens, representing new targets for novel antimicrobial agents. In this review we discuss potential of the studies on predator-prey interaction to provide alternative solutions to the problem of antibiotic resistance.
... To avoid experimental errors derived from effector-concentrations too close to the minimal requirements, we used concentrations that were 3 times the minimal requirements (i.e., 60 nM ambruticin VS-3 and 300 mM glycerol) in the quantitative analysis such as sporulation or during growth of the strains bearing promoter-lacZ fusions. For the co-incubation experiments of different myxobacteria VY2-agar supplemented with 2 g/L starch was used 46 . E. coli strains were grown on LB broth or LB agar plates (1.5% agar) 47 at 37°C. ...
Starvation induces cell aggregation in the soil bacterium Myxococcus xanthus, followed by formation of fruiting bodies packed with myxospores. Sporulation in the absence of fruiting bodies can be artificially induced by high concentrations of glycerol through unclear mechanisms. Here, we show that a compound (ambruticin VS-3) produced by a different myxobacterium, Sorangium cellulosum, affects the development of M. xanthus in a similar manner. Both glycerol (at millimolar levels) and ambruticin VS-3 (at nanomolar concentrations) inhibit M. xanthus fruiting body formation under starvation, and induce sporulation in the presence of nutrients. The response is mediated in M. xanthus by three hybrid histidine kinases (AskA, AskB, AskC) that form complexes interacting with two major developmental regulators (MrpC, FruA). In addition, AskB binds directly to the mrpC promoter in vitro. Thus, our work indicates that the AskABC-dependent regulatory pathway mediates the responses to ambruticin VS-3 and glycerol. We hypothesize that production of ambruticin VS-3 may allow S. sorangium to outcompete M. xanthus under both starvation and growth conditions in soil.
... Our results showed that the abundance of Sorangiineae and Nannocystineae were much higher than that of Cystobacterineae, which is consistent with the results indicated by prokaryotic 16S rRNA transcripts [48]. The low abundance of Cystobacterineae illustrated by culture-independent methods indicates the biases of the culture-dependent method, because species from Cystobacterineae are frequently isolated [49]. We detected sequences from all three known suborders of Myxococcales based on soil 16S rDNA sequencing in this study, but 17%−43% Myxococcales sequences were unclassified myxobacterial ASVs which could not be assigned to the three known suborders. ...
Myxobacteria are abundant micropredators in soil, and are social bacteria with multicellular behavior and producers of versatile secondary metabolites. The interaction between predator and prey populations is an important component in the soil microbial food web, and this is expected to shape the composition and dynamics of microbial communities. Here we hypothesize the regulation of bacterial abundance and community composition on soil myxobacterial community. Field investigation indicated that the relative abundance of Myxococcales in subtropical and tropical forest soil from South China was 1.49-4.74% of all the 16S rRNA gene sequences, and myxobacterial community composition differed between subtropical and tropical forest. The canonical correspondence analysis and variation partitioning analysis indicated that biotic factor (bacterial community composition) showed slightly stronger explanation for variation of myxobacteria than soil properties (soil pH and soil organic matter). Based on the rhizosphere bacterial network, the greenhouse mesocosm experiment showed that most of the myxobacterial links were with Gram-negative bacteria, except that some nodes from Haliangiacea and Polyangiaceae interacted with actinomycetes and actinomycetes-like Gram-positive bacteria. We inferred that myxobacteria preferential predation on specific bacterial taxa may explain the influence of bacteria on myxobacterial community. Further study confirming the biological process of myxobacterial predation in situ is necessary to advance the understanding of the ecological role of predation behavior in the microbial world.
... Here, we demonstrate that ExoE is functionally similar to WecP Ah , a GalNAc-1-P transferase from A. hydrophila (Merino et al., 2011) Table S2. S, species that form spores; (S), tested for sporulation but with ambiguous results; NT, sporulation not tested; N, sporulation tested and not observed (dos Santos et al., 2014;Fudou, Jojima, Iizuka, & Yamanaka, 2002;Garcia et al., 2014;Garcia & Müller, 2014a, 2014bMohr, Garcia, Gerth, Irschik, & Müller, 2012, Sanford, Cole, & Tiedje, 2002Yamamoto et al., 2014). For the exo, nfs and glt gene clusters, a reciprocal best BlastP hit method was used to identify orthologs. ...
The rod-shaped cells of Myxococcus xanthus, a Gram-negative deltaproteobacterium, differentiate to environmentally resistant spores upon starvation or chemical stress. The environmental resistance depends on a spore coat polysaccharide that is synthesized by the ExoA-I proteins, some of which are part of a Wzx/Wzy-dependent pathway for polysaccharide synthesis and export; however, key components of this pathway have remained unidentified. Here, we identify and characterize two additional loci encoding proteins with homology to enzymes involved in polysaccharide synthesis and export, as well as sugar modification, and show that six of the proteins encoded by these loci are essential for the formation of environmentally resistant spores. Our data support that MXAN_3260, renamed ExoM, and MXAN_3026, renamed ExoJ, are the Wzx flippase and Wzy polymerase, respectively responsible for translocation and polymerization of the repeat unit of the spore coat polysaccharide. Moreover, we provide evidence that three glycosyltransferases (MXAN_3027/ExoK, MXAN_3262/ExoO and MXAN_3263/ExoP) and a polysaccharide deacetylase (MXAN_3259/ExoL) are important for formation of the intact spore coat, while ExoE is the polyisoprenyl-phosphate hexose-1-phosphate transferase responsible for initiating repeat unit synthesis, likely by transferring N-acetylgalactosamine-1-P to undecaprenyl-phosphate. Together, our data generate a more complete model of the Exo pathway for spore coat polysaccharide biosynthesis and export.
... The Corallococcus genus currently comprises two validly described species, C. coralloides and C. exiguus, with C. macrosporus having been recently reassigned to the Myxococcus genus (Lang and Stackebrandt, 2009;Garcia et al., 2010). In their vegetative phase in the presence of nutrients, they produce colorless swarming growth, while on starvation they form fruiting bodies, which are pale orange or peach colored, horny or coral-shaped, hence the genus name (Garcia and Müller, 2014). Consistent with their predatory activity, several secondary metabolites with potent antibacterial and antifungal activities, such as corallopyronins, coralmycins, and corallorazines, have been characterized from Corallococcus spp. ...
Corallococcus is an abundant genus of predatory soil myxobacteria, containing two species, C. coralloides (for which a genome sequence is available) and C. exiguus. To investigate the genomic basis of predation, we genome-sequenced 23 Corallococcus strains. Genomic similarity metrics grouped the sequenced strains into at least nine distinct genomospecies, divided between two major sub-divisions of the genus, encompassing previously described diversity. The Corallococcus pan-genome was found to be open, with strains exhibiting highly individual gene sets. On average, only 30.5% of each strain’s gene set belonged to the core pan-genome, while more than 75% of the accessory pan-genome genes were present in less than four of the 24 genomes. The Corallococcus accessory pan-proteome was enriched for the COG functional category “Secondary metabolism,” with each genome containing on average 55 biosynthetic gene clusters (BGCs), of which only 20 belonged to the core pan-genome. Predatory activity was assayed against ten prey microbes and found to be mostly incongruent with phylogeny or BGC complement. Thus, predation seems multifactorial, depending partially on BGC complement, but also on the accessory pan-genome – genes most likely acquired horizontally. These observations encourage further exploration of Corallococcus as a source for novel bioactive secondary metabolites and predatory proteins.
... For cryopreservation, pieces of agar taken from an actively growing swarm colony were placed in cryotube vials and stored at À80 C. The novel strains were reactivated by placing the preserved agar pieces onto fresh agar medium. For back-up preservation, actively growing vegetative cells taken from liquid culture were stored in a À80 C freezer after the addition of 20 % (v/v) glycerol as cryoprotectant, which was followed by a slow freezing process in a Cryochamber (Mr. Frosty; Nalgene) using cold isopropanol [12]. Morphology stages of the strains were documented and determined according to a previous study [13]. ...
Bacterial strains designated MCy10943T and MCy10944T were isolated in 2014 from dried Nepalese soil samples collected in 2013 from Phukot, Kalikot, Western Nepal and Godawari, Lalitpur, Central Nepal. The novel organisms showed typical myxobacterial growth characteristics which include swarming colony and fruiting body formation on solid surfaces, and a predatory ability to lyse microorganisms. The strains were aerobic, mesophilic, chemoheterotrophic and showed resistance to various antibiotics. The major cellular fatty acids common to both organisms were C17:0 2-OH, iso-C15:0, C16:1 and iso-C17:0. The G + C content of the genomic DNA was 72-75 mol %. Phylogenetic analysis showed that the strains belong to the family Cystobacteraceae, suborder Cystobacterineae, order Myxococcales. The 16S rRNA gene sequences of both strains showed 97-98 % similarity to Archangium gephyra DSM 2261T, Cystobacter violaceus DSM 14727T, and 96.7-97 % to Cystobacter fuscus DSM 2262T and Angiococcus disciformis DSM 52716T. Polyphasic taxonomic characterisation suggested that strains MCy10943T and MCy10944T represent two distinct species of a novel genus, for which the names Vitiosangium cumulatum and Vitiosangium subalbum are proposed. The type strain of Vitiosangium cumulatum is MCy10943T (=DSM 102952T =NCCB 100600T) while for Vitiosangium subalbum is MCy10944T (=DSM 102953T =NCCB 100601T). In addition, the genera Archangium and Angiococcus, and the family Cystobacteraceae is herewith emended.
Seagrasses harbour bacterial communities with which they constitute a functional unit called holobiont that responds as a whole to environmental changes. Epiphytic bacterial communities rapidly respond to both biotic and abiotic factors, potentially contributing to the host fitness. The Lessepsian migrant Halophila stipulacea has a high phenotypical plasticity and harbours a highly diverse epiphytic bacterial community, which could support its invasiveness in the Mediterranean Sea. The current study aimed to evaluate the Halophila/Cymodocea competition in the Aegean Sea by analysing each of the two seagrasses in a zone where these intermingled, as well as in their monospecific zones, at two depths. Differences in holobionts were evaluated using seagrass descriptors (morphometric, biochemical, elemental, and isotopic composition) to assess host changes, and 16S rRNA gene to identify bacterial community structure and composition. An Indicator Species Index was used to identify bacteria significantly associated with each host. In mixed meadows, native C. nodosa was shown to be affected by the presence of exotic H. stipulacea, in terms of both plant descriptors and bacterial communities, while H. stipulacea remained almost unchanged. This study provided evidence of the competitive advantage of H. stipulacea on C. nodosa in the Aegean Sea and suggests the possible use of associated bacterial communities as a descriptor of native seagrass sustainability.
In shallow, open-water engineered wetlands, design parameters select for a photosynthetic microbial biomat capable of robust pharmaceutical biotransformation, yet the contributions of specific microbial processes remain unclear. Here, we combined genome-resolved metatranscriptomics and oxygen profiling of a field-scale biomat to inform laboratory inhibition microcosms amended with a suite of pharmaceuticals. Our analyses revealed a dynamic surficial layer harboring oxic-anoxic cycling and simultaneous photosynthetic, nitrifying, and denitrifying microbial transcription spanning nine bacterial phyla, with unbinned eukaryotic scaffolds suggesting a dominance of diatoms. In the laboratory, photosynthesis, nitrification, and denitrification were broadly decoupled by incubating oxic and anoxic microcosms in the presence and absence of light and nitrogen cycling enzyme inhibitors. Through combining microcosm inhibition data with field-scale metagenomics, we inferred microbial clades responsible for biotransformation associated with membrane-bound nitrate reductase activity (emtricitabine, trimethoprim, and atenolol), nitrous oxide reduction (trimethoprim), ammonium oxidation (trimethoprim and emtricitabine), and photosynthesis (metoprolol). Monitoring of transformation products of atenolol and emtricitabine confirmed that inhibition was specific to biotransformation and highlighted the value of oscillating redox environments for the further transformation of atenolol acid. Our findings shed light on microbial processes contributing to pharmaceutical biotransformation in open-water wetlands with implications for similar nature-based treatment systems.
purification of Archangium sp. UTMC 4504 was identified as a strain with high protease activity
Rapid and accurate strain identification of the most closely related genera Myxococcus, Corallococcus, and Pyxidicoccus can enhance the efficiency of the mining of novel secondary metabolites through dereplication. However, the commonly used 16S rRNA gene sequencing cannot accurately differentiate members of the three genera above, and the whole-genome sequencing is unable to rapidly and inexpensively provide species assignation toward a large number of isolates. To overcome the limitations, the gyrB gene was investigated as a candidate genetic marker for exploring the phylogenetic relationships of bacteria within the three genera and for developing the gyrB-based typing method. Here, the bacterial phylogeny and species affiliations of the three genera were determined based on the phylogenomic reconstruction and the analysis of digital DNA–DNA hybridization values among 90 genomes, further confirming nine novel taxa and assigning over one-third of genomes to defined species. The phylogenetic relationships of these strains based on the gyrB gene sequences were congruent with those based on their genome sequences, allowing the use of the gyrB gene as a molecular marker. The gyrB gene-specific primers for the PCR-amplification and sequencing of bacteria within the three genera were designed and validated for 31 isolates from our group collection. The gyrB-based taxonomic tool proved to be able to differentiate closely related isolates at the species level. Based on the newly proposed 98.6% identity threshold for the 966-bp gyrB gene and the phylogenetic inference, these isolates were assigned into two known species and eight additional putative new species. In summary, this report demonstrated that the gyrB gene is a powerful phylogenetic marker for taxonomy and phylogeny of bacteria within the closely related genera Myxococcus, Corallococcus, and Pyxidicoccus, particularly in the case of hundreds or thousands of isolates in environmental studies.
Cultured Myxococcota are predominantly aerobic soil inhabitants, characterized by their highly coordinated predation and cellular differentiation capacities. Little is currently known regarding yet-uncultured Myxococcota from anaerobic, non-soil habitats. We analyzed genomes representing one novel order (o__JAFGXQ01) and one novel family (f__JAFGIB01) in the Myxococcota from an anoxic freshwater spring (Zodletone spring) in Oklahoma, USA. Compared to their soil counterparts, anaerobic Myxococcota possess smaller genomes, and a smaller number of genes encoding biosynthetic gene clusters (BGCs), peptidases, one- and two-component signal transduction systems, and transcriptional regulators. Detailed analysis of thirteen distinct pathways/processes crucial to predation and cellular differentiation revealed severely curtailed machineries, with the notable absence of homologs for key transcription factors (e.g. FruA and MrpC), outer membrane exchange receptor (TraA), and the majority of sporulation-specific and A-motility-specific genes. Further, machine-learning approaches based on a set of 634 genes informative of social lifestyle predicted a non-social behavior for Zodletone Myxococcota. Metabolically, Zodletone Myxococcota genomes lacked aerobic respiratory capacities, but encoded genes suggestive of fermentation, dissimilatory nitrite reduction, and dissimilatory sulfate-reduction (in f_JAFGIB01) for energy acquisition. We propose that predation and cellular differentiation represent a niche adaptation strategy that evolved circa 500 Mya in response to the rise of soil as a distinct habitat on earth.
Importance
The Myxococcota is a phylogenetically coherent bacterial lineage that exhibits unique social traits. Cultured Myxococcota are predominantly aerobic soil-dwelling microorganisms that are capable of predation and fruiting body formation. However, multiple yet-uncultured lineages within the Myxococcota have been encountered in a wide range of non-soil, predominantly anaerobic habitats; and the metabolic capabilities, physiological preferences, and capacity of social behavior of such lineages remain unclear. Here, we analyzed genomes recovered from a metagenomic analysis of an anoxic freshwater spring in Oklahoma, USA that represent novel, yet-uncultured, orders and families in the Myxococcota. The genomes appear to lack the characteristic hallmarks for social behavior encountered in Myxococcota genomes, and displayed a significantly smaller genome size and a smaller number of genes encoding biosynthetic gene clusters, peptidases, signal transduction systems, and transcriptional regulators. Such perceived lack of social capacity was confirmed through detailed comparative genomic analysis of thirteen pathways associated with Myxococcota social behavior, as well as the implementation of machine learning approaches to predict social behavior based on genome composition. Metabolically, these novel Myxococcota are predicted to be strict anaerobes, utilizing fermentation, nitrate reduction, and dissimilarity sulfate reduction for energy acquisition. Our results highlight the broad patterns of metabolic diversity within the yet-uncultured Myxococcota and suggest that the evolution of predation and fruiting body formation in the Myxococcota has occurred in response to soil formation as a distinct habitat on earth.
Drug resistance is a critical issue in future clinical treatment. Methicillin-resistant Staphylococcus aureus (MRSA) is among the pathogens that need indispensable drug-discovery efforts. The myxobacteria are a unique group of bacteria that have recently been regarded for their potency to produce new drugs with high chemical diversity and unusual mode of actions. The present study was conducted to isolate and screen myxobacteria for the first time from Iran habitats and evaluate their antibacterial activity against the multidrug-resistant strain of S. aureus. Out of 62 soil and rotten plant samples, 51 myxobacteria were isolated. The isolates belonged to Myxococcus, Corallococcus, Pyxidicoccus, and Cystobacter genera based on morphology and 16S rRNA gene sequencing. Secondary metabolites of the selected strains were screened for activity on MDR strain with resistance to multiple antibiotic classes. The semi-purified fraction from Cystobacter sp. UTMC 4086 showed potent activity against MDR S. aureus with minimum inhibitory effect at 5 ≥ μg per mL compared with vancomycin (5 μg per mL) as well as no toxicity against Artemia salina. Hence, the strain Cystobacter sp. UTMC 4086 can be a valuable candidate for antibiotic discovery against MRSA and its metabolites can be subjected to further purification and analysis aimed at the identification of the effective chemical entity.
A non-fruiting group of myxobacteria was previously speculated to exist in nature based on metagenomics data containing uncultured members of the order Myxococcales. Here, we describe a myxobacterial strain, designated MCy10636T, which was isolated from a German soil sample collected in 2013. It exhibits swarming characteristics but atypically produces myxospores in the absence of fruiting bodies. The novel strain stains Gram-negative and Congo-red-negative and is characterized mesophilic, neutrophilic, chemoheterotrophic and microaerotolerant. Branched-chain fatty acids are the predominant cellular fatty acids over the straight-chain type, and contain the major fatty acids iso-C17 : 0 2-OH, C16 : 1, iso-C17 : 0 and iso-C15 : 0. Based on blastn results, the 16S rRNA gene sequence reveals similarity (97 %) to Aggregicoccus edonensis MCy1366T, (97 %) Myxococcus macrosporus DSM 14697T, (96 %) Corallococcus coralloides DSM2259T and Corallococcus exiguus Cc e167T. Phylogenetic analysis showed a novel lineage of MCy10636T in the family Myxococcaceae, suborder Cystobacterineae. Based on polyphasic taxonomic characterization, we propose that this unusual, non-fruiting, myxospore-forming and microaerotolerant myxobacterial strain, MCy10636T, represents a novel genus and species, Simulacricoccus ruber gen. nov., sp. nov. (DSM 106554T=NCCB 100651T).
Family Cystobacteraceae is a group of eubacteria within order Myxococcales and class Deltaproteobacteria that includes more than twenty species belonging to six genera i.e. Angiococcus, Archangium, Cystobacter, Hyalangium, Melittangium, and Stigmatella. Earlier these members have been classified based on chitin degrading efficiency such as Cystobacter fuscus and Stigmatella aurantiaca, which are efficient chitin degraders, C. violaceus a partial chitin degrader and Archangium gephyra a chitin non-degrader. Here we report the 12.5 Mbp complete genome of A. gephyra DSM 2261T and compare it with four available genomes within the family Cystobacteraceae. Phylogeny and DNA-DNA hybridization studies reveal that A. gephyra is closest to Angiococcus disciformis, C. violaceus and C. ferrugineus, which are partial chitin degraders of the family Cystobacteraceae. Homology studies reveal the conservation of approximately half of the proteins in these genomes, with about 15% unique proteins in each genome. The total carbohydrate-active enzymes (CAZome) analysis reveals the presence of one GH18 chitinase in the A. gephyra genome whereas eight copies are present in C. fuscus and S. aurantiaca. Evolutionary studies of myxobacterial GH18 chitinases reveal that most of them are likely related to Terrabacteria and Proteobacteria whereas the Archangium GH18 homolog shares maximum similarity with those of chitin non-degrading Acidobacteria.
A novel myxobacterium, strain MSr11462T, was isolated in 2015 from a soil sample collected from Kish Island beach, Persian Gulf, Iran. It displayed general myxobacterial features like Gram negative staining, rod shaped vegetative cells, gliding on solid surfaces, microbial lytic activity, fruiting body like aggregates and myxospore like structures. The strain was mesophilic, aerobic and showed chemoheterotrophic mode of nutrition. It was resistant to many antibiotics like gentamycin, polymyxin, Fusidic acid and trimethopril and the key fatty acids of whole cell hydrolysates were iso-C15:0, C16:0, iso-C17:0, C18:1 , iso-C17:1 2-OH, C18:1 2-OH, iso-C15:0 OAG (O-alkylglycerol), and C16:1 OAG. The 16S rRNA gene sequence showed highest similarity (98.60%) to Racemicystis crocea strain MSr9521T (GenBank accession no. KT59170). The phylogenetic analysis based on 16S rRNA gene sequences and MALDI-TOF data supports a novel species of the family Polyangiaceae and the genus Racemicystis. DNA-DNA hybridization showed only about 50% similarity between the novel strain and the closest species, Racemicystis crocea MSr9521T. On the basis of a comprehensive taxonomic study, we propose a novel species, Racemicystis persica sp. nov., for strain MSr11462T (DSM 103165T, NCCB 100606T).
Bacteria have been by far the most promising resource for antibiotics in the past decades and will in all undoubtedly remain an important resource of innovative bioactive natural products in the future. Actinobacteria have been screened for many years, whereas the Myxobacteria have been underestimated in the past. Even though Actinobacteria belong to the Gram-positive and Myxobacteria to the Gram-negative bacteria both groups have a number of similar characters, as they both have huge genomes with in some cases more than 10kB and a high GC content and they both can differentiate and have often cell cycles including the formation of spores. Actinobacteria have been used for the antibiotic research for many years, hence it is often discussed whether this resource has now been exhaustively exploited but most of the screening programs from pharmaceutical companies were basing on the cultivation mainly of members of the genus Streptomyces or Streptomyces like strains (e.g., some Saccharopolyspora, Amycolatopsis or Actinomadura species) by use of standard methods so that many of the so called “neglected” Actinobacteria were overlooked the whole time. The present review gives an overview on the state of the art regarding new bioactive compounds with a focus on the marine habitats. Furthermore, the evaluation of Myxobacteria in our ongoing search for novel anti-infectives is highlighted.
Myxococcus xanthus, like other myxobacteria, is a social bacterium that moves and feeds cooperatively in predatory groups. On surfaces, rod-shaped vegetative cells move in search of the prey in a coordinated manner, forming dynamic multicellular groups referred to as swarms. Within the swarms, cells interact with one another and use two separate locomotion systems. Adventurous motility, which drives the movement of individual cells, is associated with the secretion of slime that forms trails at the leading edge of the swarms. It has been proposed that cellular traffic along these trails contributes to M. xanthus social behavior via stigmergic regulation. However, most of the cells travel in groups by using social motility, which is cell contact-dependent and requires a large number of individuals. Exopolysaccharides and the retraction of type IV pili at alternate poles of the cells are the engines associated with social motility. When the swarms encounter prey, the population of M. xanthus lyses and takes up nutrients from nearby cells. This cooperative and highly density-dependent feeding behavior has the advantage that the pool of hydrolytic enzymes and other secondary metabolites secreted by the entire group is shared by the community to optimize the use of the degradation products. This multicellular behavior is especially observed in the absence of nutrients. In this condition, M. xanthus swarms have the ability to organize the gliding movements of thousands of rods, synchronizing rippling waves of oscillating cells, to form macroscopic fruiting bodies, with three subpopulations of cells showing division of labor. A small fraction of cells either develop into resistant myxospores or remain as peripheral rods, while the majority of cells die, probably to provide nutrients to allow aggregation and spore differentiation. Sporulation within multicellular fruiting bodies has the benefit of enabling survival in hostile environments, and increases germination and growth rates when cells encounter favorable conditions. Herein we review how these social bacteria cooperate and review the main cell-cell signaling systems used for communication to maintain multicellularity.
Summary
The first documented study on bacterial predation was carried out using myxobacteria three quarters of a century ago (Beebe, 1941). Since then, many predatory strains, diverse hunting strategies, environmental consequences, and potential applications have been reported by groups all over the world. Now we know that predatory bacteria are distributed in a wide variety of environments and that interactions between predatory and non-predatory populations seem to be the most important factor in bacterial selection and mortality in some ecosystems. Bacterial predation has now been proposed as an evolutionary driving force. The structure and diversity of the predatory bacterial community is beginning to be recognized as an important factor in biodiversity due to its potential role in controlling and modeling bacterial populations in the environment. In this paper we review the current understanding of bacterial predation, going over the strategies used by the main predatory bacteria to kill their prey. We have also reviewed and integrated the accumulated advances of the last 75 years with the interesting new insights that are provided by the analyses of genomes, predatomes, predatosomes, and other comparative genomics studies, focusing on potential applications that derive from all of these areas of study.
Bacterial strains SBSr002T and SBSr003T were isolated in 2007 from dried soil samples containing decaying plant material. The organisms were recognized as myxobacteria by growth- stage characteristics, forming swarming colonies and fruiting bodies on agar and on filter paper. These strains were unusual for their ring-like or halo colony appearance in an agar. Both isolates were characterized as bacteriolytic, non-cellulolytic, mesophilic, aerobic and chemoheterotrophic and showed resistance to various antibiotics. GC-MS analysis of their cellular fatty acids revealed rather large quantities of docosahexaenoic acid, and they also both contained eicosapentaenoic acid, arachidonic acid and docosapentaenoic acid. Strain SBSr003T was previously identified as the producer organism of a novel class of potent antiviral metabolites that were called aetheramides. The G + C content of the genomic DNA was 68.0-68.9 mol%. Phylogenetic analysis revealed that both strains belong within the family Polyangiaceae, suborder Sorangiineae, order Myxococcales. Their 16S rRNA gene sequences showed the highest similarity (97-99 %) to sequences derived from clones of uncultured bacteria, 95-96 % similarity to Byssovorax cruenta and Sorangium cellulosum and 94 % similarity to Chondromyces apiculatus. The results of a polyphasic taxonomic characterization suggested that strains SBSr002T and SBSr003T represent two distinct species of a novel genus, Aetherobacter gen. nov., for which the names Aetherobacter fasciculatus sp. nov. (type strain SBSr002T=DSM 24601T=NCCB 100377T) and Aetherobacter rufus sp. nov. (type strain SBSr003T=DSM 24628T=NCCB 100378T) are proposed. The type species of Aetherobacter is Aetherobacter fasciculatus.
ABSTRACT A novel myxobacterium MCy1366T (Ar1733) was isolated in 1981 from a soil sample collected from a region near Tokyo, Japan. It displayed general myxobacterial features like Gram negative staining, rod shaped vegetative cells, gliding on solid surfaces, microbial lytic activity, fruiting body-like aggregates and myxospore-like structures. The strain was mesophilic, aerobic and showed chemoheterotrophic mode of nutrition. It was resistant to many antibiotics like cephalosporin C, kanamycin, gentamycin, hygromycin B, polymyxin and bacitracin and the key fatty acids of whole cell hydrolysates were iso-C15:0, iso-C17:0, and iso-C17:0 2-OH. The genomic G+C content of the novel strain is 65.6 mol%. The 16S rRNA gene sequence showed highest similarity (97.60%) to "Stigmatella koreensis" strain KYC-1019 (not validly described taxon, GenBank accession no. EF112185). The phylogenetic analysis based on 16S rRNA gene sequences and MALDI-TOF data revealed a novel branch in the family Myxococcaceae. DNA-DNA hybridization showed only 28% similarity between the novel strain and the closest species, Corallococcus exiguus DSM 14696T (97% 16S rRNA gene sequence similarity). A recent isolate from a Switzerland soil sample and designated reference strain, MCy10622 displayed 99.9% 16S rRNA gene similarity and showed almost the same characteristics with MCy1366T. Since some morphological features like fruiting body like aggregates were barely reproducible in the type strain, the newly isolated strain MCy10622 was also intensively studied. On the basis of a comprehensive taxonomic study, we propose a novel genus and species, Aggregicoccus edonensis gen. nov., sp. nov., for strain MCy1366T and MCy10622. The type strain for the genus Aggregicoccus is MCy1366T (=DSM 27872T =NCCB 100468T).
Fifty-eight terrestrial and salt-tolerant myxobacteria were isolated from the saline-alkaline soils collected from Xinjiang, China. Based on the morphologies and the 16S rRNA gene sequences, these isolates were assigned into 6 genera, Myxococcus, Cystobacter, Corallococcus, Sorangium, Nannocystis and Polyangium. All the strains grew better with 1% NaCl than without NaCl. Some Myxococcus strains were able to grow at 2% NaCl concentration, suggesting that these strains may be particular type of terrestrial myxobacteria.
Myxococcus xanthus is a member of the Myxococcales order within the deltaproteobacterial subdivision. Here, we report the whole-genome shotgun sequence of the type IV pilus
(T4P) defective strain DZF1, which includes many genes found in strain DZ2 but absent from strain DK1622.
Myxococcus xanthus is a member of the Myxococcales order within the Deltaproteobacteria subdivision. The myxobacteria reside in soil, have relatively large genomes, and display complex life cycles. Here, we report the whole-genome shotgun sequence of strain DZ2, which includes unique genes not found previously in strain DK1622.
Hallmarks of the myxobacteria include the formation of spore-filled fruiting bodies in response to starvation and synthesis of secondary metabolites. Myxococcus stipitatus forms morphologically highly distinct fruiting bodies and produces secondary metabolites with antibiotic or cytotoxic activities. Here, we present the 10.35-Mb genome sequence of M. stipitatus strain DSM 14675.
Doxycycline and rifampicin deplete essential Wolbachia from filarial nematodes that cause lymphatic filariasis or onchocerciasis, resulting in blocked worm development and death.
However, doxycycline is contraindicated for children and pregnant/breastfeeding women, as is rifampicin in the latter group
with the additional specter of possible resistance development in Mycobacterium spp. Novel antibiotics with a narrower spectrum would aid in eliminating filarial diseases. Corallococcus coralloides synthesizes corallopyronin A, a noncompetitive inhibitor of RNA polymerase ineffective against Mycobacterium spp. Corallopyronin A depleted Wolbachia from infected insect cells (1.89 Thus the antibiotic is effective against intracellular bacteria despite the many intervening
surfaces (blood vessels, pleura, worm cuticle) and membranes (worm cell, vesicle, Wolbachia inner and outer membranes). Corallopyronin A is an antibiotic to develop further for filariasis elimination without concern
for cross-resistance development in tuberculosis.
Corallococcus coralloides, like most other myxobacteria, undergoes a developmental program culminating in the formation of fruiting bodies. C. coralloides fruiting bodies are morphologically distinct from those of other fruiting myxobacteria for which full-length genome sequences
are available. The genome sequence of the 10.0-Mb C. coralloides genome is presented herein.
Myxobacteria are common in terrestrial habitats and well known for their formation of fruiting bodies and production of secondary metabolites. We studied a cluster of myxobacteria consisting only of sequences of marine origin (marine myxobacteria cluster, MMC) in sediments of the North Sea. Using a specific PCR, MMC sequences were detected in North Sea sediments down to 2.2 m depth, but not in the limnetic section of the Weser estuary and other freshwater habitats. In the water column, this cluster was only detected on aggregates up to a few meters above the sediment surface, but never in the fraction of free-living bacteria. A quantitative real-time PCR approach revealed that the MMC constituted up to 13% of total bacterial 16S rRNA genes in surface sediments of the North Sea. In a global survey, including sediments from the Mediterranean Sea, the Atlantic, Pacific and Indian Ocean and various climatic regions, the MMC was detected in most samples and to a water depth of 4300 m. Two fosmids of a library from sediment of the southern North Sea containing 16S rRNA genes affiliated with the MMC were sequenced. Both fosmids have a single unlinked 16S rRNA gene and no complete rRNA operon as found in most bacteria. No synteny to other myxobacterial genomes was found. The highest numbers of orthologues for both fosmids were assigned to Sorangium cellulosum and Haliangium ochraceum. Our results show that the MMC is an important and widely distributed but largely unknown component of marine sediment-associated bacterial communities.
Two species of the myxobacterial genus Archangium have been grown in pure culture in liquid medium for extended periods of time. The medium consisted of casein hydrolysate, glucose, galactose, and a vitamin solution in distilled water. The nitrogen sources appropriate for these organisms must be further defined and the vitamin requirements, if any, must be more precisely determined, but it does not appear that these species of Archangium require any particularly exotic growth factors.
The myxobacteria are Gram-negative, unicellular, gliding bacteria with rod-shaped vegetative cells (Fig. 1). Because of their gliding movement, colonies develop as thin, film-like, spreading swarms, particularly on media low in organic constituents (lean media) (Fig. 2). Under starvation conditions, the myxobacteria undergo an impressive process of cooperative morphogenesis: the vegetative cells aggregate and pile up, and the resulting cell mass differentiates into a fruiting body (Fig. 3). Myxobacterial fruiting bodies show various degrees of complexity, both morphologically and structurally. They typically measure between 50 and 500 μm, and they can thus be easily seen with the naked eye. Within the maturing fruiting body, a cellular differentiation takes place during which the vegetative cells convert into short, fat, optically refractile myxospores (Figs. 1 and 3). The myxospores are desiccation resistant and allow the organism to survive unfavorable environmental conditions.
The gliding bacteria are, in all likelihood, a phylogenetically heterogeneous group. The uniting character, gliding motility, may have the same taxonomic importance and reliability as flagellation. To compound the problem, we still know so little about these fascinating bacteria that our generalizations are of necessity based on relatively few observations. Thus, an organism that has lost its gliding motility may not be recognizable as a member of this group. This question may be more than theoretically important, as illustrated by the taxonomic difficulties centering around the Cytophaga-Flavobac-terium complex.
My.xo.coc.ca' les . M.L. fem. pl. n. Myxococcaceae type family of order; ‐ ales ending to denote an order; M.L. fem. pl. n. Myxococcales the Myxococcaceae order.
Proteobacteria / Deltaproteobacteria / Myxococcales
Strain CMU-1, identified as a member of Angiococcus disciformis (Thaxter) Jahn 1924, was isolated from aquatic habitats in the fossa region of Davis Lake (Vestaburg Bog), Michigan. The myxobacter produced orange fruiting bodies consisting of numerous disk-shaped to oblate spheroid-shaped sporangia (average, 40 by 27 μm; 15 μm thick). The sporangia comprising the fruiting body occurred singly or were clumped in irregular masses upon a solid substrate. Mature myxospores ranged in shape from irregular spheres (1 μm in diameter) to ovals (1 by 1.5 μm). Vegetative rods were motile by gliding and measured 0.5 to 0.75 by 3 to 14 μm. The guanine plus cytosine content of the deoxyribonucleic acid extracted from A. disciformis CMU-1 was 68.4 mol%. Strain CMU-1 (ATCC 33172) has the properties recorded in the original description of Myxococcus disciformis by Thaxter, and it is herein proposed as the neotype strain of this organism. Because the myxospores were contained within sporangia, the organism cannot belong to the genus Myxococcus, and we propose that it properly belongs in the genus Angiococcus Jahn 1924.
1 The myxobacteria are Gram-negative, unicellular bacteria with rod-shaped vegetative cells (Fig. 1). Because of their gliding movement, colonies develop as thin, spreading swarms, particularly on media low in organic constituents (Fig. 2). Under starvation conditions, the myxobacteria undergo an impressive process of cooperative morphogenesis: the vegetative cells aggregate into large mounds and then form a fruiting body by directed cell movement (Fig. 3). Myxobacterial fruiting bodies show various degrees of complexity. They typically measure between 50 and 500 µm and can be seen with the naked eye. Within the maturing fruiting body the vegetative cells convert into short, optically refractile myxospores (Figs. 1 and 3). The myxospores are desiccation resistant and allow the organis ...
At the meeting of the Judicial Commission
of the ICSB held in Jerusalem on the 29th
March, 1973 an Ad Hoc Committee was
appointed (Minute 22) to organize a review of
the currently valid names of bacteria with the
object of retaining only names for those taxa
which were adequately described and, if
cultivable, for which there was a Type, Neotype
or Reference strain available; to compile these
names under the title of Approved Lists of
Bacterial Names and to publish the lists in the
International Journal of Systematic Bacteriology,
to become effective on January 1, 1980...
A list of the names that have been proposed for the several taxa of the order Myxobaterales (Schizomycetes) is annotated. The original publications of descriptions and names have been examined and verified. The validity of publication and legitimacy of the names have been evaluated on the basis of the directives of the International Code of Nomenclature of the Bacteria and Viruses. Each entry includes the author(s) of the name, year of publication, page on which the name is proposed, nomenclatural status, homonyms and synonyms, both objective and subjective. The list includes the names of 4 Classes, 11 Orders, 9 Families, 2 Subfamilies, 33 Genera, 13 Sections, 206 Species and 20 Varieties, a total of 298 entries and a bibliography of 102 references.
Four undisturbed sphagnum-bogs of the Hohes Venn (Belgium) were investigated for fruiting myxobacteria and aerobic heterotrophic eubacteria. The peat samples were collected at a depth of 10 cm below the vegetation layer. The pH of of the samples was 3.7, the water content 91 %, the oxygen content 2.58 mg/l and the degree of humosity was between H3 and H5. Three species of bacteriolytic fruiting myxobacteria were found with varying frequency: Myxococcus fulvus (8.8 % of samples), Myxococcus xanthus (2.5 %) and Polyangium spec. (6.8 %). Cellulolytic fruiting myxobacteria did not occur. Counts of aerobic heterotrophic eubacteria resulted in an average of 2.1 X 10⁵ colony-forming units/g of fresh wet samples. Of 105 aerobic heterotrophic eubacterial isolates 62 % were Gram-positive, predominantly bacilli; the 38 % Gram-negative bacteria were predominantly fluorescent pseudomonads. In the peat layers the degradation of cellulose is carried out by a consortium of eubacteria, cytophagas and filamentous fungi, whereas fruiting myxobacteria are not involved in this process. © 1984, Gustav Fischer Verlag, Stuttgart/New York. All rights reserved.
The myxobacterium Corallococcus coralloides is the producer of the antibiotic compound corallopyronin A, which is currently in preclinical evaluation. To obtain suitable amounts of this antibiotic, the production strain C. coralloides B035 was cultured in large volumes, which in the addition to the isolation of the target molecule facilitates the detection of additional metabolites of this myxobacterial strain (corallorazines A-C). Corallorazine A is a new structural type of dipeptide composed of a dehydroalanine and a glycine moiety that are linked via a semiaminal bond, thus forming a piperazine ring. The latter is further connected via an amide bond to an unusual aliphatic acyl chain.
Among myxobacteria only strains of Myxococcus fulvus are able to produce in addition to the well known myxothiazol A (1) an analog, myxothiazol Z (2), with an ester-type β-methoxyacrylate pharmacophore. Feeding experiments with labeled precursors established its biosynthesis from the amide (1) presumably via an O-methyl imidate (3).
Myxopyronins and corallopyronins are structurally related α-pyrone antibiotics from myxobacteria. They are thought to represent a highly promising compound class for the development of broad-spectrum antibacterial therapeutic agents, because of their ability to inhibit RNA polymerase through interaction with the "switch region", a recently identified novel drug target. Here we describe the identification and characterization of the myxopyronin biosynthetic pathway from Myxococcus fulvus Mx f50. A detailed comparison with the recently identified corallopyronin biosynthetic pathway revealed the genetic and biochemical basis, thus explaining the observed structural differences between the two natural product families. Directed mutagenesis procedures for M. fulvus Mx f50 were developed to enable functional studies and pathway modifications. Our work provided new insights into myxopyronin biosynthesis and led to the production of a novel and unexpected myxopyronin derivative.
In cave sediments of the French Jura Mountains four Myxobacteria species could be identified: Myxococcus fulvus, Corallococcus coralloides, Archangium gephyra and Myxococcus virescens. Aquatic habitats reveal higher Myxobacteria counts and increased diversity than terrestrial habitats. A. gephyra and M. virescens were promoted by aquatic conditions. C. coralloides predominates in surface-near subterraneous sediments, whereas M. fulvus predominates in zones with increased depth. The sediment texture influenced the distribution of species. The data allow a comparison of karst systems in Europe. A high correlation was found between the average number of Myxobacteria species and the average subterranean temperature. The ecological valence and the cardinal temperatures of the species most likely control this. Myxobacteria possibly play a role in the control of subterraneous biofilm growth.
Myxobacteria were isolated in Japan from soils, decaying plant materials, and tree bark. The isolation methods we have used are the rabbit dung method, placing soil on bacterial smears, the filter paper method, and the agar medium method. Placing soil on bacterial smears was easy to manage. Addition of dealkaline lignin stimulated formation of well- differentiated fruiting bodies on agar medium. This made it possible to investigate the morphology of fruiting bodies of myxobacteria on the agar medium in the laboratory. The myxobacteria isolated and purified were found to be strains of the genera Myxococcus and Archangium. Isolates were identified as Myxococcus stipitatus, Myxococcus fulvus, Myxococcus coralloides, and Archangium gephyra. A new species Myxococcus flavescens is proposed on the basis of morphological characteristics and production of diffusible light yellow pigment. All the tested strains gave positive reactions in catalase and urease. The DNA base composition of the myxobacteria examined ranged from 65 to 67mol% of guanine plus cytosine. The major quinone was menaquinone with 8 isoprenoid units (MK-8). The major cellular fatty acids were iso 15:0, iso 17:0, and 16:1.
140 leaf samples were examined, 73 of which ( = 52.1%) contained myxobacteria. Three species of the genus Myxococcus, M. virescens, M. fulvus and M. coralloides, could be found more or less frequently in the phyllosphere of woody plants and annuals. Archangium gephyra was observed only once. There was no significant difference in the occurrence of myxobacteria between evergreen leaves and leaves from deciduous trees and shrubs. Fruit-trees yielded the best results.
The base composition of the deoxyribonucleic acid of 11 strains of Nannocystis exedens varied between 70 and 72 mol% guanine plus cytosine (G+C). Therefore it falls into the G+C range known from other myxobacteria, i.e., 67 to 72 mol%.
Rhizopodin was isolated as cytostatic and weakly antifungal macrolide (1) and later characterized as potent actin-depolymerizing agent. It is produced by the myxobacterium Myxococcus stipitatus, which enables a fermentative supply of the drug for biological studies. We here report a revised structure that characterizes rhizopodin (2) as the first known dimeric bis-lactone exhibiting side chains that terminate in N-methyl-vinylformamide groups, which are otherwise found in smaller marine toxins also targeting the actin cytoskeleton. Compound 2 might function as bivalent inhibitor forming ternary complexes with actin which would explain its high efficacy.
Antibiotics from Gliding Bacteria, 45. — Phenalamides, New HIV-1 Inhibitors from Myxococcus stipitatus Mx s40
We report on the isolation and structure elucidation of the phenalamides A1 (1), A2 (2), A3 (3), B (4), and C (5), amides from alaninol and ω-phenyl-substituted unsaturated carboxylic acids (a pentaene carboxylic acid in 1 — 4, and a tetraene carboxylic acid chromophore in 5). Compounds 1 — 3 are E/Z isomers with the configuration: 6Z for 1, 4 represents 8-methyl-1, and for 5 we determined the 10,11-double bond in 2 to be epoxidated. C-16 in 1 has the S configuration, as revealed by ozonisation and isolation of the (2S)-(+)-2-methyl-4-phenylbutyric acid. By comparison of their respective CD spectra all the other centers of chirality in 1 should have the same stereochemistry as in the related compound myxalamid B. 1 seems to be identical to stipiamide. First results of enrichment experiments show that the biogenesis of 1 starts with phenylalanine, which after transamination and decarboxylation is connected with propionate and acetate units to generate the highly unsaturated fatty acid. The second amino acid unit alanine terminates the biosynthesis.
Myxobacteria are widely distributed in soil and oceanic sediment with a phylogeographic separation at high levels of classification. However, it is unclear whether freshwater environments, from which there has been no isolation report of myxobacteria since 1981, are habitats for myxobacteria. In this study, we investigated the presence of myxobacteria in lake mud using a two-step strategy. First, we constructed two universal bacterial libraries from the V3-V4 (V34) and V6-V8 (V678) hypervariable regions of 16S rRNA gene sequences. High-throughput 454 pyrosequencing revealed that myxobacteria were one of the major bacterial groups in the lake mud. They accounted for 5.77% of the total sequences and 7.52% of the total operational taxonomic units (OTUs) at a phylogenetic distance of 0.03. The community composition and taxonomic structure of the mud myxobacterial community were further analysed using myxobacteria-enriched libraries targeting the V34 and V678 regions, which were amplified with Cystobacterineae- and Sorangineae-specific primer pairs respectively. Phylogenetic analysis showed that the limnetic myxobacteria exhibited closer relationships to their soil than their marine relatives, but there were also exclusive taxa of limnetic myxobacteria detected. These results, together with a survey on available GenBank data, indicate that lake mud is a primary habitat for myxobacteria.
Crude extracts of vegetative cells of the cellulolytic myxobacter Polyangium cellulosum contained significant levels of the enzymes of the tricarboxylic acid cycle and the glyoxylate cycle. Key enzymes of glycolysis and the pentose phosphate shunt were also detected. Specific activities of hexokinase and fructose- 1,6-diphosphate aldolase exhibited a 10-fold increase when the cells were grown in complex medium containing glucose. Cytochromes of a, b, and c type were demonstrated. By the use of a dispersly growing strain of P. cellulosum, its generation time was determined to be 22–24 h. This study suggests that the organism probably uses glycolysis and citric acid cycle for complete oxidation of glucose. The exact role of the glyoxylate cycle and pentose phosphate shunt cannot be deduced from this study. This is the first report on the study of intermediary carbohydrate metabolism in any member of the family Polyangiaceae.
Myxococcus xanthus, the best known of the myxobacteria, is a Gram-negative bacterium that produces numerous interesting molecules in its growth medium. It is shown here to excrete a glycopeptide with blood anticoagulant activity. This molecule, whose amino acid composition shows a high ratio of glutamic acid and serine, and whose glycan moiety contains acetylglucosamine and acetylgalactosamine, is one of several low molecular weight, glycan-containing molecules also excreted by this bacterium.
The synthesis of the natural siderophore myxochelin B (1S) and its enantiomer 1R is described. 1S and 1R served as precursors for the synthesis of new hexadentate siderophores, the myxochelins C (7S) and CR (7R), D (14S) and DR (14R), E (19S) and (RS)-F (26R, S), with 2,3-dihydroxybenzoate (DHB) ligands and the simple backbones of asymmetric 1,2,n-triamino-n-alkanes. For the myxochelins C, D, E and F n is 6 (from lysine), 5 (from ornithin), 4 (from asparagine amide) and 7 [from (±)-2-aminopimelic acid], respectively. The additional amino functions in the starting compounds were provided by dehydration of the corresponding primary amides, and subsequent reduction of the nitriles by cobalt boride in methanol. All new siderophores supply bacteria with ferric ions with an efficiency which depends on their chain length and stereochemistry. They show significant activity against the cytomegalo virus.
From cultures of Melittangium lichenicola, Archangium gephyra and Myxococcus stipitatus, thirteen new β-methoxyacrylate (MOA) fungicides related to myxothiazols (1) have been isolated. Melithiazols A (2a), D (2b), K (2c), and L (2d) are characterized by a thiazoline–thiazole system, whereas melithiazols B (3a), E (3b), F (3c), G (3d), H (3e), I (3f), M (3g), and N (3h) are bis(thiazoles). Melithiazol C (4), as the first representative of this class of compounds, contains only one thiazole ring. The structures were established on the basis of spectroscopic data, and confirmed in the case of melithiazol E (3b), including its relative configuration, by an X-ray structure analysis. The absolute configuration of melithiazols A (2a) and B (3a) was determined by degradation and CD spectroscopy. Antifungal and cytotoxic activities, inhibition of NADH oxidation, and lipophilicities of melithiazols 2–4, myxothiazols 1, and strobilurin-type compounds are compared.
Pure cultures of many myxobacteria could be quickly obtained by treating fruiting bodies with highly dosed mixtures of antibiotics
Bacteriophages for Myxococcus xanthus of similar morphology to phage Mx4 were isolated from cultures of a variety of myxobacterial species. Phages similar to Mx1 and Mx8 were obtained by infecting M. xanthus with one of the phages of the Mx4 group that had been treated with either UV light or a chemical mutagen.
The DNA molecules from the phages were characterized by electron microscopy. One phage, Mx113, contains an unusual type of terminal redundancy revealed by examination of denatured and re-annealed DNA.
Several of the phages of the Mx4 group and the other two new phages, Mx113 and Mx811, were found capable of transducing genetic markers in M. xanthus.
One phage, Mx416, was characterized in more detail. It establishes true lysogens in M. xanthus; the phage plaques on both a non-motile mutant and also on a wild-type host although it is restricted in the latter.
The myxobacterium, Corallococcus (Myxococcus) coralloides strain Cc c127, could not utilize mono- and disaccharides, but maltotriose and the polysaccharides starch, amylose, amylopectin, and pullulan stimulated growth. Radioactive CO2 was set free from 14C-labeled starch. When starch was degraded, small amounts of maltose and glucose accumulated in the culture supernatant. Maltotriose, however, appeared only temporarily. Outside the cells, the trisaccharide could not be split into glucose and maltose. Pullulan was hydrolyzed exclusively into a trisaccharide which during growth was immediately consumed. Hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and phosphoglucomutase could readily be demonstrated in cell extracts, but fructose-1,6-diphosphate aldolase was present with low activity only. The data suggest that intracellular glucose is metabolized mainly via the pentose phosphate pathway.
1.
The carotenoids of Myxococcus fulvus strain Mx f2 were analyzed. The carotenoid content of cultures growing logarithmically in the dark was found to be about 0.003% of the dry weight of acetone extracted cells. This value rose to 0.03% in logarithmically growing cultures in light, and to 0.06% in illuminated late log-phase cultures grown in a fermenter.
2.
The organism synthesizes about 50 to 60 different carotenoids, 24 of which could be isolated in sufficient quantities to be identified.
3.
The identified pigments were: phytoene (1), phytofluene (2), -carotene (3), neurosporene (4), -carotene (5), lycopene (6), torulene (7), 3,4-dehydro-lycopene (8) — 4-keto--carotene (9), 4-keto-torulene (10) — 1,2-dihydro-1-hydroxy--carotene (11), 1,2-dihydro-1-OH-lycopene (12), 1,2-dihydro-1-OH-torulene (13), 3-(or 4-)-OH-torulene (14), 1,2-dihydro-3,4-dehydro-1-OH-lycopene (15) — 4,4-diketo--carotene (16), 4,4-diketo-lycopene (17), 1,2-dihydro-4,2-diketo-torulene (18) — 1,2-dihydro-1-OH-4-keto--carotene (19) — a 2-fatty acid ester of 1,2-dihydro-1,2-dihydroxy-4-keto-torulene (22) — and the fatty acid esters of the two glucosides myxobacton (23), and myxobactin (24). The hydroxyl groups of two pigments could not be located: 1,2-dihydro-trihydroxy-4-keto-torulene (21), and a tetrahydroxy carotenoid with a spheroidene-like chromophore and a nonconjugated ring (20).
4.
2-Acyl-1,2-dihydro-1,2-dihydroxy-4-keto-torulene (22) appears to be the first true carotenoid fatty acid ester found in a bacterium. The fatty acid part of the ester was variable and consisted mainly of C16:0, C16:1, C18:0, C18:1, and tentatively identified C21:0.
5.
Most of the carotenoids of M. fulvus occur only in trace amounts. The bulk of the pigments is composed of 3 compounds: the two acyl glucosides and 4-ketotorulene.
Come to the fore: The novel myxobacterial metabolite myxoprincomide is easy to overlook in the complex LC-MS data recorded for the metabolome of Myxococcus xanthus DK1622, such that advanced analytical techniques were needed for its discovery. By enhancing genomics-based natural products research with powerful analytical tools for in-depth metabolome mining, two additional such "hidden" metabolites have been uncovered.