Systematic and Applied Microbiology

Published by Elsevier
Print ISSN: 0723-2020
The 0.2 microm filtration of sea water samples from the Mediterranean Sea (Bay of Calvi, Corsica), collected from 10 m and 35 m depth led to the isolation of several gram-negative bacterial strains able to grow on full-strength media as well as on diluted media. The analysis of the 16S rRNA gene sequences and estimation of the phylogenetic relationships of these facultative oligotrophic bacteria indicated that they grouped into two phylogenetic branches. The strains RE10F/2, RE10F/5 (10 m depth samples) and RE35/F12 (35 m depth samples) were assigned to the gamma-subclass, while RE35F/1 (35m depth sample) was assigned to the alpha-4-subclass of the Proteobacteria. The strains RE10/F2 and RE10/F5 were most closely related to species and strains of the Pseudoalteromonas group, whereas the strain RE35F/12 placed adjacent to the family Vibrionaceae. The phylogenetic analysis of strain RE35F/1 revealed that this bacterium clusters with marine strains and species of the aerobic anoxygenic phototrophic bacteria Erythrobacter as well as Erythromicrobium and more distantly to Sphingomonas spp. Supplementary to those genotypic classifications the chemotaxonomic signatures including the major respiratory lipoquinone systems, the cellular fatty acid compositions as well as the polyamine contents of the bacteria were investigated. The isolated organisms displayed differences in their physiological and biochemical properties to already described strains belonging to the same genera or families, as revealed by the comparative 16S rRNA analysis. Despite the fact that these bacteria were isolated from a 0.2 microm filtrate, the cultured organisms which were all rod-shaped, displayed width dimensions ranging from 0.4 up to 0.7 microm, indicating that these bacteria were starvation forms at the time of isolation and not ultramicrobacteria as defined by Torella and Morita (1981) or by Schut et al. (1993). Because our isolated strains represent potentially new taxa, this first investigation on 0.2 pm filterable bacteria from the Western Mediterranean Sea supports the hypothesis that this bacterial fraction contributes to the diversity of marine bacteria.
The C12O gene (catA gene) encodes for catechol 1,2-dioxygenase, which is a key enzyme involved in the first step catalysis of the aromatic ring in the ortho-cleavage pathway. This functional gene can be used as a marker to assess the catabolic potential of bacteria in bioremediation. C12OF and C12OR primers were designed based on the conserved regions of the CatA amino acid sequence of Actinobacteria for amplifying the catA gene from the genus Gordonia (16 Gordonia representing 11 species). The amplified catA genes (382bp) were sequenced and analyzed. In the phylogenetic tree based on the translated catA amino acid sequences, all the Gordonia segregated clearly from other closely related genera. The sequence similarity of the catA gene in Gordonia ranged from 72.4% to 99.5%, indicating that the catA gene might have evolved faster than rrn operons or the gyrB gene at the inter-species level. A single nucleotide deletion of the catA gene was observed in Gordonia amicalis CC-MJ-2a, Gordonia rhizosphera and Gordonia sputi at nucleotide position 349. This deletion led to an encoding frame shift downstream of 11 amino acid residues, from WPSVAARAPAP to GHPWRPAHLHL, which was similar to most of the non-Gordonia Actinobacteria. Such variations might influence the catabolic activities or substrate utilization patterns of catechol 1,2-dioxygenase among Gordonia.
Trimethyl-1,2-dihydroxypropyl-ammonium (TM) originates from the hydrolysis of the parent esterquat surfactant, which is widely used as softener in fabric care. Based on test procedures mimicking complex biological systems, TM is supposed to degrade completely when reaching the environment. However, no organisms able to degrade TM were isolated nor has the degradation pathway been elucidated so far. We isolated a Gram-negative rod able to grow with TM as sole source of carbon, energy and nitrogen. The strain reached a maximum specific growth rate of 0.4(h-1) when growing with TM as the sole source of carbon, energy and nitrogen. TM was degraded to completion and surplus nitrogen was excreted as ammonium into the growth medium. A high percentage of the carbon in TM (68% in continuous culture and 60% in batch culture) was combusted to CO2 resulting in a low yield of 0.54 mg cell dry weight per mg carbon during continuous cultivation and 0.73 mg cell dry weight per mg carbon in batch cultures. Choline, a natural structurally related compound, served as a growth substrate, whereas a couple of similar other quaternary aminoalcohols also used in softeners did not. The isolated bacterium was identified by 165-rDNA sequencing as a strain of Pseudomonas putida with a difference of only one base pair to P. putida DSM 291T. Despite their high identity, the reference strain P. putida DSM 291T was not able to grow with TM and the two strains differed even in shape when growing on the same medium. This is the first microbial isolate able to degrade a quaternary ammonium softener head group to completion. Previously described strains growing on quaternary ammonium surfactants (decyltrimethylammonium, hexadecyltrimethylammonium and didecyldimethylammonium) either excreted metabolites or a consortium of bacteria was required for complete degradation.
In the paper by Schaad et al. [24] on reclassification of several xanthomonads, nomenclatural errors were made. The name Xanthomonas smithii subsp. citri proposed for the former taxon X. campestris pv. citri ( = X. axonopodis pv. citri) is illegitimate. Following the reinstatement of X. citri (ex Hasse 1915) Gabriel et al. [9] as a validly published name, Young et al. [34] wrote that the reinstatement of this epithet was based on a description that was inadequate in terms of modern practice for the purpose of formal classification. This report was subsequently summarized by the International Committee on the Systematics of Bacteria (ICSB) Subcommittee on the Taxonomy of the Genus Pseudomonas and Related Organisms [32] as implying rejection of the epithet, which the Subcommittee itself appeared to endorse. As we now understand, in accord with the International Code of Nomenclature of Prokaryotes (‘the Code’—hitherto the International Code of Nomenclature of Bacteria [14]) the Judicial Commission of the ICSP only may reject a name for precisely specified reasons (Rule 56a). We also misinterpreted the subsequent establishment of the pathovar ‘‘citri’’ within Xanthomonas axonopodis [29] as further evidence for rejection of reinstatement of X. citri [9]. Finally, believing that the epithet ‘‘citri’’ had been rejected, we followed rule 23a of the Code [14] and proposed an illegitimate specific epithet ‘‘smithii’’ (which also required establishing the subspecies epithet ‘‘smithii’’ replacing ‘‘malvacearum’’; see rule 13a [14]). In fact, X. citri Gabriel et al. 1989 was a legitimate, validly published name that was allowed to fall into abeyance because of the inadequacies perceived in its description. Schaad et al. [24] indicated their support for the conclusions of Gabriel et al. [9] but included DNA–DNA reassociation data indicated as necessary by for modern classification [26,31]. One purpose of this note is to recognize by effective publication the species related to pathogenic xanthomonads of citrus. The second purpose is to avoid confusion in plant pathological literature by replacing the illegitimate subspecies name X. smithii subsp. ‘‘smithii’’ with X. citri subsp. ‘‘malvacearum’’. For that purpose, corrected protologues for those species and subspecies are reported here: X. citri subsp. citri and X. citri subsp. malvacearum; X. fuscans subsp. fuscans and X. fuscans subsp. aurantifolii; and X. alfalfae subsp. alfalfae and X. alfalfae subsp. citrumelonis. We also present (Table 1) GenBank accession numbers for the intergeneric spacer (ITS) sequences for the type strains proposed in this note [24].
Six isolates of a new genus of anaerobic archaebacteria, named Pyrodictium, were isolated from a submarine solfataric field off Vulcano, Italy. These disc-shaped organisms grew at at least 110°C with an optimum around 105°C, and formed highly unusual networks of fibres. They were hydrogen-sulphur-autotrops. During growth in a fermenter, pyrite was formed. Two species can be distinguished: Pyrodictium occultum - which has a G + C-content of 62 mol%, and, as the dominant component in its cell envelope, a glycoprotein with a molecular weight of 172000 - and Pyrodictium brockii - which has a G + C-content of 51.5 to 56.6 mol%, a protein of molecular weight 150000 as its major cell envelope component, and whose growth yield is greatly increased in the presence of yeast extract.
Strains of Mycoplasma ovine/caprine serogroup 11, isolated from infertile sheep, were compared to the type strain, 2D, and to strains of the cattle pathogen M. bovigenitalium, including the type strain, PG11. Examination of these strains by growth inhibition and immune fluorescence tests showed strong serological cross reactivity between M. serogroup 11 and M. bovigenitalium but not with other ruminant mycoplasmas. Substrate oxidation and growth studies did not show any consistent differences between M. serogroup 11 and M. bovigenitalium strains; all strains assigned to both groups were adapted to the utilisation of a small range of organic acids as energy sources. DNA:DNA hybridisation, carried out between DIG labelled reference strains of M. serogroup 11 and M. bovigenitalium and field isolates of these two mycoplasmas showed a particularly close relationship with hybridisation rates all greater than 70% and, mostly, closer to 90%. Sequencing of the 16S ribosomal RNA gene region of the M. serogroup 11 and M. bovigenitalium strains as well as the respective type strains revealed very high overall homologies of 99.5%. In summary, the results showed a very close phenotypic and genotypic relatedness between these two ruminant mycoplasmas which justifies their classification into a single species.
"Pseudomonas oxalaticus" strain Ox1T (= DSM 1105T), which was described as an oxalate-decomposing bacterium, was reinvestigated to clarify its taxonomic position. 16S ribosomal DNA sequence comparisons demonstrated that this species is phylogenetically related to the species of the genus Ralstonia. and represents a new species. The result of the DNA-DNA hybridization value was supported in this placement. Strain Ox1T is closely related to Ralstonia eutropha with a less than 60% DNA-DNA hybridization value. The new name Ralstonia oxalatica comb. nov. is proposed to strain Ox1T, on the basis of these results and previously published data for the G+C content of the genomic DNA and the phenotypic characters.
Taxonomical analysis of two genetically distinguished Lactobacillus strains isolated from traditional Chinese fermented vegetables 'Suan cai' was performed. They formed L-lactate from glucose, were facultatively heterofermentative, and had a DNA G+C content of 53-54mol%. They fermented D- and L-arabinose. They produced lactate, ethanol and acetate from gluconate at a molar ratio of 1.1:0.4:0.7. Phylogenetic analysis of 16S rDNA revealed that the two strains were closely related to L. perolens. DNA-DNA hybridization analysis revealed that the two strains were different from L. perolens type strain DSM 12744 and formed a separate cluster with L. perolens DSM 12745. G + C molar content of DNA of the former is 51%, whereas those of the latter strains were in the range of 53-54%. Based on the results, we propose that the new species be named L. harbinensis sp. nov. and that L. perolens DSM 12745 be reclassified as L. harbinensis DSM 12745. The type strain of L. harbinensis DSM 16991T (= AHU 1762T = SBT 10908T).
An acid phosphatase, designated SapS, hydrolyzing p-nitrophenyl phosphate (pNPP), was identified and characterized from the culture supernatant of a Staphylococcus aureus strain isolated from vegetables. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the protein indicated an estimated molecular mass of 30 kDa. The enzyme displayed optimum activity at 40 degrees C and pH 5. Characterization of the phosphatase in a reconstitution assay showed that MgCl2 and Triton X-100, respectively, restored maximal activity, but not CaCl2 The phosphatase activity was affected by EDTA and sodium molybdate. The DNA sequence encoding SapS was cloned and sequenced. The putative acid phosphatase gene encodes a protein of 296 amino acids with a 31-residue signal peptide. Database searches revealed significant structural homology of SapS to several proteins belonging to the bacterial class C family of nonspecific acid phosphatases. Comparison of the sequences indicated that despite a low level of overall conservation between the proteins, four conserved sequence motifs could be identified.
Colonic Bacteroides include several species which, by their population level and activities, are significant contributers to the metabolic activity and health of man and animals. Yet, the understanding of their ecology has been hampered by the lack of highly specific and reliable enumeration techniques. Based on 16S rRNA sequence comparisons within the available database, we have designed an 18-mer oligonucleotide that targets a region common to-and specific for the Bacteroides-Porphyromonas-Prevotella group. We have tested the specificity of the probe and its usefulness for studies of human faecal samples. Under experimentally optimized hybridization conditions, the probe was shown to similarly recognize the rDNA obtained from 40 strains representing 8 species of the Bacteroides-Porphyromonas-Prevotella group. Importantly, it did not recognize 31 strains of microorganisms representing 8 genera of the dominant human faecal microbiota. Among selected colonies of dominant microorganisms of the faecal flora of two human individuals, strains identified as B. vulgatus by immunoblots using a species-specific monoclonal antibody were all detected by the probe. Colony hybridization was used to enumerate total Bacteroides-group microorganisms in faecal specimen from children and adults. The probe described therein was further used in quantitative RNA blots to monitor fluctuations of the Bacteroides-group versus Bifidobacterium genus in frozen faecal samples from a child between 85 and 125 days of age. It will be applicable to similar investigations of other anaerobic environments.
The phenotypic identification of the classical propionibacteria is essentially still problematic and alternative techniques for the identification of the various species are required. A rapid and sensitive technique for the routine identification of the classical propionibacteria, based on the amplification of 16S rRNA genes using the polymerase chain reaction and the subsequent restriction endonuclease digestion of the PCR products, was previously described. Although this technique enabled differentiation between the various classical species examined it was only evaluated on a limited number of type and reference strains. During this study, the taxonomic relationship between 135 Propionibacterium strains from diverse ecological niches, representing four classical species was investigated using this PCR/RFLP technique. Visual differentiation between the classical Propionibacterium was possible after restriction endonuclease digestion of the PCR products obtained using primers 16sP1-16sP4 and 16sP3-16sP4 with the restriction endonucleases HaeIII, AluI and HpaIII, respectively. With the exception of strains independently identified as "P. rubrum" and "P. sanguineum", the results of this study confirm the consolidation of the "old" species into the various classical species as they currently exist. It was therefore concluded that the PCR/RFLP protocol is suitable for the rapid and routine identification of the classical propionibacteria.
One hundred and fifty-six strains isolated from corn (Zea mays L.), forage paddy rice (Oryza sativa L.), sorghum (Sorghum bicolor L.) and alfalfa (Medicago sativa L.) silages prepared on dairy farms were screened, of which 110 isolates were considered to be lactic acid bacteria (LAB) according to their Gram-positive and catalase-negative characteristics and, mainly, the lactic acid metabolic products. These isolates were divided into eight groups (A-H) based on the following properties: morphological and biochemical characteristics, γ-aminobutyric acid production capacity, and 16S rRNA gene sequences. They were identified as Weissella cibaria (36.4%), Weissella confusa (9.1%), Leuconostoc citreum (5.3%), Leuconostoc lactis (4.9%), Leuconostoc pseudomesenteroides (8.0%), Lactococcus lactis subsp. lactis (4.5%), Lactobacillus paraplantarum (4.5%) and Lactobacillus plantarum (27.3%). W. cibaria and W. confusa were mainly present in corn silages, and L. plantarum was dominant on sorghum and forage paddy rice silages, while L. pseudomesenteroides, L. plantarum and L. paraplantarum were the dominant species in alfalfa silage. The corn, sorghum and forage paddy rice silages were well preserved with lower pH values and ammonia-N concentrations, but had higher lactic acid content, while the alfalfa silage had relatively poor quality with higher pH values and ammonia-N concentrations, and lower lactic acid content. The present study confirmed the diversity of LAB species inhabiting silages. It showed that the differing natural populations of LAB on these silages might influence fermentation quality. These results will enable future research on the relationship between LAB species and silage fermentation quality, and will enhance the screening of appropriate inoculants aimed at improving such quality.
For a long time, the identification of the Leuconostoc species has been limited by a lack of accurate biochemical and physiological tests. Here, we use a combination of RAPD, 16S rDNA sequencing, and 16S rDNA fragment amplification with specific primers to classify different leuconostocs at the species and strain level. We analysed the molecular diversity of a collection of 221 strains mainly isolated from traditional French cheeses. The majority of the strains were classified as Leuconostoc mesenteroides (83.7%) or Leuconostoc citreum (14%) using molecular techniques. Despite their presence in French cheeses, the role of L. citreum in traditional technologies has not been determined, probably because of the lack of strain identification criteria. Only one strain of Leuconostoc lactis and Leuconostoc fallax were identified in this collection, and no Weissella paramesenteroides strain was found. However, dextran negative variants of L. mesenteroides, phenotypically misclassified as W. paramesenteroides, were present. The molecular techniques used did not allow us to separate strains of the three L. mesenteroides subspecies (mesenteroides, dextranicum and cremoris). In accordance with previously published results, our findings suggest that these subspecies may be classified as biovars. Correlation found between phenotypes dextranicum and mesenteroides of L. mesenteroides and cheese technology characteristics suggests that certain strains may be better adapted to particular technological environments.
Cowpea [Vigna unguiculata (L.) Walp.] is an important legume crop and yet its rhizobia have not been well characterized in many areas. In the present study, sequence analysis of the bacterial 16S-23S rRNA internal transcribed spacer (ITS) region was performed to characterize genetically 76 indigenous cowpea rhizobia from five different geographic regions (Okinawa, Miyazaki, Kyoto, Fukushima and Hokkaido) of Japan. The sequence analysis clustered all isolates in the genus Bradyrhizobium. They were conspecific with B. japonicum, B. yuanmingense, B. elkanii and Bradyrhizobium sp., although none of them grouped with B. liaoningense, B. canariense, B. betae or B. iriomotense. B. yuanmingense was only isolated from the southern region (Okinawa) where it achieved the highest frequency of 69%. B. japonicum was predominant at Miyazaki, Fukushima and Hokkaido with more than 60% of the isolates. B. elkanii was mainly recorded in the southern (Okinawa: 31%, Miyazaki: 33%) and middle (Kyoto: 33%) regions. This species was present at a very low frequency in Fukushima and absent in Hokkaido in the northern area. Bradyrhizobium sp. like-strains were absent in the southern part (Okinawa, Miyazaki) but were concentrated either in the middle regions with 67% of Kyoto isolates and 28% of Fukushima isolates, and in the northern region with 40% of the Hokkaido isolates. This study revealed a geographical distribution of cowpea bradyrhizobia which seemed to be related to the differences in the environmental characteristics (soil type and soil pH, temperature, climate, moisture) of the different regions in Japan.
Members of the highly diverse bacterial phylum Verrucomicrobia are globally distributed in various terrestrial and aquatic habitats. They are key players in soils, but little is known about their role in aquatic systems. Here, we report on the design and evaluation of a 16S rRNA-targeted probe set for the identification of Verrucomicrobia and of clades within this phylum. Subsequently, the probe set was applied to a study concerning the seasonal abundance of Verrucomicrobia in waters of the humic lake Grosse Fuchskuhle (Germany) by catalyzed reporter deposition fluorescence in situ hybridization. The lake hosted diverse Verrucomicrobia clades in all seasons. Either Spartobacteria (up to 19%) or Opitutus spp. (up to 7%) dominated the communities, whereas Prosthecobacter spp. were omnipresent in low numbers (<1%). Verrucomicrobial abundance and community composition varied between the seasons, and between more and less humic basins, but were rather stable in oxic and seasonally anoxic waters.
Several novel N(2)-fixing Burkholderia species associated with plants, including legume-nodulating species, have recently been discovered. Presently, considerable interest exists in studying the diazotrophic Burkholderia species, both for their ecology and their great potential for agro-biotechnological applications. However, the available methods used in the identification of these Burkholderia species are time-consuming and expensive. In this study, PCR species-specific primers based on the 16S rRNA gene were designed, which allowed rapid, easy, and correct identification of most known N(2)-fixing Burkholderia. With this approach, type and reference strains of Burkholderia kururiensis, B. unamae, B. xenovorans, B. tropica, and B. silvatlantica, as well as the legume-nodulating B. phymatum, B. tuberum, B. mimosarum, and B. nodosa, were unambiguously identified. In addition, the PCR species-specific primers allowed the diversity of the diazotrophic Burkholderia associated with field-grown tomato and sorghum plants to be determined. B. tropica and B. xenovorans were the predominant species found in association with tomato, but the occurrence of B. tropica with sorghum plants was practically exclusive. The efficiency of the species-specific primers was validated with the detection of B. tropica and B. xenovorans from DNA directly recovered from tomato rhizosphere soil samples. Additionally, using PCR species-specific primers, all of the legume-nodulating Burkholderia were correctly identified, even from single nodules collected from inoculated common bean plants. These primers could contribute to rapid identification of the diazotrophic and nodulating Burkholderia species associated with important crop plants and legumes, as well as revealing their environmental distribution.
The diversity of 16S-23S rDNA intergenic spacer regions (ISR) among cellulolytic myxobacterial strains was assayed. Agarose gel electrophoresis of PCR amplification products from ten strains shows that there are at least four copies of rRNA operons in the genus Sorangium, based on their size and restriction enzymatic digest maps. There are two sequence organization patterns: tRNA(Ile)-tRNA(Ala)-containing ISR and tRNA-lacking ISR. The tRNA-containing ISRs are highly similar among strains and within a strain (more than 98% similarity) and contain the essential functional regions, such as a ribonuclease III recognition site and an antiterminator recognition site boxA. The tRNA-lacking ISR has no such functional sites that are important for yielding mature rRNA, which suggests that this type of rRNA operons might be degenerate. The tRNA-lacking ISR is divided into two types based on their sizes and sequences, which exhibits about 90% similarity within each type. Thus, the tRNA-lacking ISR polymorphisms can be used to discriminate among different strains of sorangial species.
We screened samples from high temperature biotopes for 16S rRNA genes of the novel archaeal phylum "Nanoarchaeota". Positive PCR amplifications were obtained from Yellowstone National Park, Uzon Caldera, and an abyssal vent system. These sequences form a cluster with the sequence of "Nanoarchaeum equitans", indicating a wide distribution of this phylum.
We used direct recovery of bacterial 16S rRNA gene sequences to investigate the bacterial diversity under Acacia tortilis subsp. raddiana, a legume tree naturally growing in the dry land part of Senegal (West Africa). Microbial DNA was purified directly from soil samples and subjected to PCR with primers specific for bacterial 16S rRNA gene sequences. 16S rDNA clone libraries were constructed from two soil samples taken at two dates, i.e. June 25th 1999 (dry season) and August 28th 1999 (rainy season) at depths of 0.25-0.50 m and at 3 m distance from the stem. The 16S rDNA of 117 clones was partially sequenced. Phylogenetic analysis of these sequences revealed extensive diversity (100 phylotypes). Comparative sequence analysis of these clones identified members of the Gammaproteobacteria (35% of the phylotypes) as the most important group, followed by the Firmicutes division with 24%. Alphaproteobacteria, Betaproteobacteria, Acidobacteria and Actinobacteria were found to be less represented. Our data suggest that bacterial communities under Acacia tortilis subsp. raddiana might differ according to the season. The relative compositions of the populations is different in both samples: the Acidobacteria are present in a much higher percentage in the dry season than in the rainy season sample while the inverse effect is observed for the members of the other groups. Within the Gammaproteobacteria we found a shift between the dry season and the rainy season from pseudomonads to Acinetobacter and Escherichia related organisms.
The formation of a stable viscous foam on activated sludge aeration basin surfaces is a world wide problem. Foam is usually comprised of filamentous bacteria occurring predominantly in the mixed liquor. The lack of availability of pure cultures of most filaments and the limited amount of characterisation data available for them, means that our current understanding of their taxonomic position is very poor and their relationship to other bacteria are not known. 16S rDNA sequencing was used in an attempt to identify the bacteria in a foaming sample from the Centurion Waste Water Treatment Plant in Gauteng South Africa.
Bacteria of the Cytophaga-Flavobacterium-Bacteroides phylum (CFB-phylum) are numerically important members of many microbial communities. A suite of five 16S rRNA-targeted oligonucleotide probes for members of this group is described which was designed to dominantly target bacteria of the CFB-phylum that are found in particular habitats. For this we initially performed a literature survey-for the sources and sites of isolation of hitherto described members of the CFB-phylum. Probe CFB286 is mostly complementary to the 16S rRNA of species originally isolated from freshwater habitats, however, detects some marine and soil isolates and is the only probe which includes some food isolates. Probe CFB563 detects marine as well as animal-associated isolates. Probe CFB719, which also detects some environmental isolates, and probe CFB972 are mostly targeting animal-associated isolates. All probes are complementary to a variety of human-associated species within the CFB-phylum which, in the data set investigated (October 1998), made up 46% of all 16S rRNA sequences from the CFB-phylum. We conclude that it is difficult to find habitat-specific probes for members of the CFB-phylum and that the design of probes for monophyletic groups should remain the standard approach. Applicability of the probes for fluorescence in situ hybridization and specificity for single cell detection were evaluated for the four mentioned probes whereas the fifth, probe CFB1082, which almost exclusively targets human-associated species, was not further characterized. The new probes are of limited determinative value and should be used together with the already established probes for the CFB-phylum. It is the hybridization pattern observed for a given cell or culture with the enlarged probe set that is suggestive for its affiliation with a defined group within the CFB-phylum.
Bacteroides spp. represent a prominent bacterial group in human intestinal microbiota with roles in symbiosis and pathogenicity; however, the detailed composition of this group in human feces has yet to be comprehensively characterized. In this study, the molecular diversity of Bacteroides spp. in human fecal microbiota was analyzed from a seven-member, four-generation Chinese family using Bacteroides spp. group-specific 16S rRNA gene clone library analysis. A total of 549 partial 16S rRNA sequences amplified by Bacteroides spp.-specific primers were classified into 52 operational taxonomic units (OTUs) with a 99% sequence identity cut-off. Twenty-three OTUs, representing 83% of all clones, were related to 11 validly described Bacteroides species, dominated by Bacteroides coprocola, B. uniformis, and B. vulgatus. Most of the OTUs did not correspond to known species and represented hitherto uncharacterized bacteria. Relative to 16S rRNA gene universal libraries, the diversity of Bacteroides spp. detected by the group-specific libraries was much higher than previously described. Remarkable inter-individual differences were also observed in the composition of Bacteroides spp. in this family cohort. The comprehensive observation of molecular diversity of Bacteroides spp. provides new insights into potential contributions of various species in this group to human health and disease.
Tripeptidase (PepT) and dipeptidase (PepV), the enzymes located in the final stage of the intracellular proteolytic system, were demonstrated to be distributed widely in lactic acid bacteria, especially in lactococci. Both the tripeptidase genes (pepT) and dipeptidase genes (pepV) of 15 lactococcal strains consisting of the type and domestic strains were cloned and sequenced using normal and TAIL PCR methods. Amino acid sequences of these enzymes were highly conserved among strains. Evolutionary distance trees based on the sequence of 1239 nucleotides of pepT and 1416 nucleotide of pepV showed a similar cluster as that obtained from the 1499 fragment of the 16S rRNA. Based on this profile, the species Lactococcus lactis is reasonably divided into three subspecies groups, subsp. lactis, cremoris, and hordniae, as in the current classification. Figure of trees from pepT and pepV were essentially identical to each other and slightly more intricate than that from 16S rRNA. The K nuc values obtained from pepT and pepV genes were approximately ten times as high as that from 16S rRNA. Considering these results, phylogenetic analysis based on pepT and pepV genes may aid in a more precise index of classification of L. lactis subspecies. PepT and PepV seem to have evolved in similar directions in lactococci.
The use of Single Base C-Sequencing of the first 500 bases of the 16S rRNA-gene (SBCS) combined with capillary electrophoresis was evaluated for the identification of reference strains of 30 different species within the genus Streptococcus. For SBCS, only dd-CTP's are used in the sequencing reactions instead of the four dideoxy bases and the primer is fluorescently labeled. The reproducibility, interlaboratory exchangeability and discriminative power of this method were studied by comparing the patterns obtained in three laboratories under highly standardized conditions. The interlaboratory reproducibility proved to be high, enabling the construction of a common database for the identification of strains belonging to the streptococcal species studied. Most of the examined species generated distinguishable profiles. SBCS did not differentiate between the closely related species S. constellatus and S. intermedius. Also S. thermophilus and S. vestibularis as well as S. mitis and S. pneumoniae showed highly resembling profiles. The previously reported heterogeneity within the species S. equinus was reflected by SBCS. For all other species, strains belonging to the same species generated indistinguishable patterns. In conclusion, Single Base C-sequencing of the first 500 bases of the 16S rRNA-gene could be a useful and widely applicable method for the identification of bacteria at the species level, with the added advantage of being more rapid and easier to automatize than full sequence determination.
Molecular and biochemical assays were used to determine the identification of thermophilic bacilli isolated from New Zealand milk powder. One hundred and forty one isolates of thermophilic bacilli were classified into six species using biochemical profiles. Geobacillus stearothermophilus represented 56% of the isolates. All isolates were also analysed by randomly amplified polymorphic DNA (RAPD) analysis, with 45 types identified. Amplification of the 16S-23S rDNA internal spacer region produced two to eight amplification products per strain. The patterns from gel electrophoresis of the internal spacer region amplicons formed two major groupings suggesting the possibility of two distinct species. Partial sequences of 16S rDNA from representatives from each group were compared with sequences in GeneBank and were found to match the 16S rDNA sequences of B. flavothermus and G. thermoleovorans. Primers were designed for these species and used to screen an arbitrary selection of 59 of the dairy isolates. This enabled the identification of 28 isolates as B. flavothermus and 31 isolates as Geobacillus species and these appear to be the predominant isolates in the New Zealand milk powder samples examined. Comparison of the fragment pattern generated by amplification of the 16S-23S rDNA internal spacer region is a simple method to differentiate thermophilic Bacillus species associated with the dairy industry.
The aims of this study were to characterize and determine intraspecies and interspecies relatedness of Actinobacillus pleuropneumoniae to Actinobacillus lignieresii and Actinobacillus suis by sequence analysis of the ribosomal operon and to find a species-specific area for in situ detection of A. pleuropneumoniae. Amplification and sequence analysis of the 16S-23S rDNA ribosomal intergenic sequence (RIS) from the three species showed the existence of two RIS's, differing by about 100 bp. Both sequences contained a region resembling the ribonuclease III cleavage site found in Escherichia coli. The smaller RIS contained a Glu-tRNA gene, and the larger one contained genes encoding Ile-tRNA and Ala-tRNA. These tRNA's showed a high sequence homology to the respective tRNA genes found in E. coli. Sequence analysis of the RIS's showed a high degree of genetic similarity of 24 strains of A. pleuropneumoniae. The larger RIS's were different between the 3 species tested. The sequence of the 16S ribosomal gene was determined for 8 serotypes of A. pleuropneumoniae. These sequences showed only minor base differences, indicating a close genetic relatedness of these serotypes within the species. An oligonucleotide DNA probe designed from the 16S rRNA gene sequence of A. pleuropneumoniae was specific for all strains of the target species and did not cross react with A. lignieresii, the closest known relative of A. pleuropneumoniae. This species-specific DNA probe labeled with fluorescein was used for in situ hybridization experiments to detect A. pleuropneumoniae in biopsies of diseased porcine lungs.
Over the past few years, there has been an increasing interest in making oligonucleotides specific for ammonia-oxidizing bacteria (AOB), in order to detect and monitor these slow growing bacteria in environmental samples, in enrichment cultures and in wastewater treatment plants. Based on 16S rDNA sequences, a broad selection of oligonucleotides have been designed, either encompassing all known AOB in the beta-subgroup of the Proteobacteria (beta AOB), or subclasses within beta AOB. Thirty different oligonucleotides have so far been published, with varying specificity. The first AOB-specific oligonucleotides published were obtained as a result of an alignment of only eleven 16S rDNA sequences from AOB. Including the present study, there are now forty nearly full length 16S rDNA sequences available from these bacteria, in addition to a number of partial sequences, so that an improved evaluation of the published oligonucleotides can be done. Two new 16S rRNA gene sequences from Nitrosospira are presented here, in a phylogenetic analysis containing every 16S rRNA gene sequences (> 1 kb) available from AOB. On the basis of an alignment of all these sequences, combined with searches in the nucleotide sequence databases, an evaluation of the thirty published oligonucleotides is presented. The analysis expose the strength and weakness of each oligonucleotide and discuss the use of oligonucleotides specific for 16S rRNA genes in future studies of AOB. The present work also identifies one new, broad range primer, specific for the AOB in the beta-subgroup of the Proteobacteria.
The 16S-23S rDNA intergenic spacer regions (ISR) of different streptococcal species and subspecies were amplified with primers derived from the highly conserved flanking regions of the 16S rRNA and 23S rRNA genes. The single sized amplicons showed a uniform pattern for S. agalactiae, S. dysgalactiae subsp. dysgalactiae (serogroup C), S. dysgalactiae subsp. equisimilis (serogroup G), S. dysgalactiae subsp. dysgalactiae (serogroup L), S. canis, S. phocae, S. uberis, S. parauberis, S. pyogenes and S. equi subsp. equi, respectively. The amplicons of S. equi subsp. zooepidemicus, S. porcinus and S. suis appeared with 3, 5 and 3 different sizes, respectively. ISR of selected strains of each species or subspecies investigated were sequenced and multiple aligned. This allowed a separation of ISR into regions, with 7 regions for S. agalactiae, S. dysgalactiae subsp. dysgalactiae (serogroup C), S. dysgalactiae subsp. equisimilis (serogroup G), S. dysgalactiae subsp. dysgalactiae (serogroup L), S. canis, S. phocae, S. pyogenes and S. suis, 8 regions for S. uberis and S. parauberis and mostly 9 regions for S. equi subsp. equi, S. equi subsp. zooepidemicus and S. porcinus. Region 4, encoding the transfer RNA for alanine (tRNA(Ala)), was present and identical for all isolates investigated. The size and sequence of ISR appears to be a unique marker for streptococci of various species and subspecies and could be used for bacterial identification. In addition the size and sequence variations of ISR of S. equi subsp. zooepidemicus, S. porcinus and S. suis allows a molecular typing of isolates of these species possibly useful in epidemiological aspects.
The genes of ribosomal RNA are the most popular and frequently used markers for bacterial phylogeny and reconstruction of insect-symbiont coevolution. In primary symbionts, such as Buchnera and Wigglesworthia, genome economization leads to the establishment of a single copy of these sequences. In phylogenetic studies, they provide sufficient information and yield phylogenetic trees congruent with host evolution. In contrast, other symbiotic lineages (e.g., the genus Arsenophonus) carry a higher number of rRNA copies in their genomes, which may have serious consequences for phylogenetic inference. In this study, we show that in Arsenophonus triatominarum the degree of heterogeneity can affect reconstruction of phylogenetic relationships and mask possible coevolution between the symbiont and its host. Phylogenetic arrangement of individual rRNA copies was used, together with a calculation of their divergence time, to demonstrate that the incongruent 16S rDNA trees and low nucleotide diversity in the secondary symbiont could be reconciled with the coevolutionary scenario.
Twenty-seven new Rhizobium isolates were obtained from root nodules of wild and crop legumes belonging to the genera Vicia, Lathyrus and Pisum from different agroecological areas in central and southern Italy. A polyphasic approach including phenotypic and genotypic techniques was used to study their diversity and their relationships with other biovars and species of rhizobia. Analysis of symbiotic properties and stress tolerance tests revealed that wild isolates showed a wide spectrum of nodulation and a marked variation in stress tolerance compared with reference strains tested in this study. All rhizobial isolates (except for the isolate CG4 from Galega officinalis) were presumptively identified as Rhizobium leguminosarum biovar viciae both by their symbiotic properties and the specific amplification of the nodC gene. In particular, we found that the nodC gene could be used as a diagnostic molecular marker for strains belonging to the bv. viciae. RFLP-PCR 16S rDNA analysis confirms these results, with the exception of two strains that showed different RFLP-genotypes from those of the reference strains of R. leguminosarum bv. viciae. Analysis of intraspecies relationship among strains by using the RAPD-PCR technique showed a high level of genetic polymorphism, grouping our isolates and reference strains into six different major clusters with a similarity level of 20%. Data from seven parameters of phenotypic and genotypic analyses were evaluated by using principal component analysis which indicated the differences among strains and allowed them to be divided into seven different groups.
Bacterial denitrification in agricultural soils is a major source of nitrous oxide, a potent greenhouse gas. This study examined the culturable bacterial population of denitrifiers in arable field soils in potato (Solanum tuberosum L.) production and denitrification genes (nir, nor and nos) and 16S rDNA in those isolates. Enrichments for culturable denitrifiers yielded 31 diverse isolates that were then analysed for denitrification genes. The nitrous oxide reductase (nosZ) gene was found in all isolates. The majority of isolates ( approximately 90%) contained the cnorB nitric oxide reductase gene, with the remainder containing the qnorB gene. Nitrite reductase genes (nirS and nirK) were amplifiable from most of the isolates, and were segregated between species similar to previously isolated denitrifiers. Isolated strains were preliminarily identified using fatty acid methyl ester analysis and further identified using 16S rDNA sequencing. The majority of isolates (21) were classified as Pseudomonas sp., with smaller groups of isolates being most similar to Bosea spp. (4), Achromobacter spp. (4) and two isolates closely related to Sinorhizobium/Ensifer spp. Phylogenetic trees were compared among nosZ, cnorB and 16S rDNA genes for a subset of Pseudomonas strains. The trees were mostly congruent, but some Pseudomonas sp. isolates grouped differently depending on the gene analysed, indicating potential horizontal gene transfer of denitrification genes. Although Bosea spp. are known denitrifiers, to the best of our knowledge this is the first report of isolation and sequencing of denitrification genes from this bacterial genus.
Comparative sequence analysis of 16S ribosomal (r)RNAs or DNAs of Bacillus alvei, B. laterosporus, B. macerans, B. macquariensis, B. polymyxa and B. stearothermophilus revealed the phylogenetic diversity of the genus Bacillus. Based on the presently available data set of 16S rRNA sequences from bacilli and relatives at least four major "Bacillus clusters" can be defined: a "Bacillus subtilis cluster" including B. stearothermophilus, a "B. brevis cluster" including B. laterosporus, a "B. alvei cluster" including B. macerans, B. maquariensis and B. polymyxa and a "B. cycloheptanicus branch".
Separation of amplified V3 region from 16S rDNA by denaturing gradient gel electrophoresis (PCR-DGGE) and 16S-23S rDNA intergenic spacer region polymorphism (ISR-PCR) analyses were tested as tool for differentiation of staphylococcal strains commonly isolated from fermented sausages. Variable V3 regions of 25 staphylococcal reference strains and 96 wild strains of species belonging to the genera Staphylococcus, Micrococcus and Kocuria were analyzed. PCR-DGGE profiles obtained were species-specific for S. sciuri, S. haemolyticus, S. hominis, S. auricularis, S. condimenti, S. kloosi, S. vitulus, S. succinus, S. pasteuri, S. capitis and S. (Macrococcus) caseolyticus. Moreover, 7 groups could be distinguished gathering the remaining species as result of the separation of the V3 rDNA amplicons in DGGE. Furthermore, the combination of the results obtained by PCR-DGGE and ISR-PCR analyses allowed a clear differentiation of all the staphylococcal species analysed, with exception of the pairs S. equorum-S. cohnii and S. carnosus-S. schleiferi. The suitability of both molecular techniques and of the combination their results for the identification of staphylococci was validated analysing partial nucleotide sequence of the 16S rDNA of a representative number of wild strains.
The aim of our study was to obtain data for the molecular characterization of bdellovibrio bacteria, which were recently split into the genus Bdellovibrio and the newly designated genus Bacteriovorax. We determined the 16S rDNA sequences of five reference strains and performed a phylogenetic analysis including published 16S rRNA sequences of bdellovibrios. A comparison of the secondary structure showed significant differences in two regions of the 16S rRNAs of the species Bdellovibrio bacteriovorus, Bacteriovorax starrii, and Bacteriovorax stolpii. In addition, ribotyping techniques gave specific hybridization patterns and revealed that two rRNA operons are present in the investigated strains. A hybridization probe derived from the genetic locus hit, associated with the host independent (HI) phenotype of B. bacteriovorus, was found to be specific for this species. Sequence comparison of the hit locus revealed few base pair changes between host independent (HI) and host dependent (HD) strains. Ribotyping and hybridization experiments using the hit probe were applied to characterize bdellovibrio strains isolated from the gut of animals and humans and one isolate from sewage.
The 16S rDNA encoding the small subunit ribosomal RNA were amplified by PCR, cloned, and sequenced from 16 strains of Xylella fastidiosa originating from nine different hosts. In pair-wise comparisons, X. fastidiosa strains showed a maximum variation of 1.0% or 14 nucleotide positions. When all 16 sequences were considered as a set, 54 variable positions were found. Analysis of the sequence data indicated that the X. fastdiosa strains formed three rDNA groups. Group one includes Pierce's disease and mulberry leaf scorch strains; Group two, periwinkle wilt, plum leaf scald, phony peach, oak leaf scorch, and elm leaf scorch strains; and Group three, citrus variegated chlorosis and coffee leaf scorch strains. All X. fastidiosa strains exhibited significantly higher levels of sequence heterogeneity (63 to 83 nucleotide positions) when compared to species from Xanthomonas and Stenotrophomonas. Our data demonstrate that 16S rDNA sequence data could provide valuable information for future classification of X. fastidiosa at the sub-species level.
Intestinal spirochetes (Brachyspira spp.) are causative agents of intestinal disorders in animals and humans. Phylogenetic analysis of cloned 16S rRNA genes from biopsies of the intestinal mucosa of the colon from two Swedish 60-years old adults without clinical symptoms revealed the presence of intestinal spirochetes. Seventeen clones from two individuals and 11 reference strains were analyzed and the intestinal spirochetes could be divided into two lineages, the Brachyspira aalborgi and the Brachyspira hyodysenteriae lineages. All of the clones grouped in the B. aalborgi lineage. Moreover, the B. aalborgi lineage could be divided into three distinct phylogenetic clusters as confirmed by bootstrap and signature nucleotide analysis. The first cluster comprised 6 clones and the type strain B. aalborgi NCTC 11492T. The cluster 1 showed a 16S rRNA gene similarity of 99.4-99.9%. This cluster also harbored the only other strain of B. aalborgi isolated so far, namely strain W1, which was subjected to phylogenetic analysis in this work. The second cluster harbored 9 clones with a 98.7 to 99.5% range of 16S rDNA similarity to the B. aalborgi cluster 1. Two clones branched distinct and early of the B. aalborgi line forming the third cluster and was found to be 98.7% similar to cluster 1 and 98.3-99.1% to cluster 2. Interestingly, this shows that considerable variation of intestinal spirochetes can be found as constituents of the colonic microbiota in humans, genetically resembling B. aalborgi. The presented data aid significantly to the diagnostic and taxonomic work on these organisms.
Correlation plot of ITS sequence similarity values versus DNA-DNA hybridization values for Bradyrhizobium strains from genospecies I to V, VII and IX to XI. A horizontal line marks the 60% DNA-DNA hybridization level that is used to delineate genospecies. A vertical line marks the 95.5% ITS sequence similarity level. Above this level strains belong to the same genospecies. The points marked a and b represent the pairs of strains (USDA 110 [genospecies Ia], LMG 6238 T [genospecies I]) and (USDA 110, LMG 4252 [genospecies I}, respectively.
In an extension of a previous small-scale test to assess the use of 16S-23S rDNA internal transcribed spacer (ITS) sequences for rapid grouping of bradyrhizobia, we have sequenced the ITS region of 32 isolates of Bradyrhizobium that had previously been studied using AFLP and DNA-DNA hybridizations. We also included representatives of Afipia and Rhodopseudomonas. Our results indicate that ITS sequences are very diverse among bradyrhizobia. Nevertheless, for most of the bradyrhizobia, the grouping of ITS sequences was in line with AFLP results and DNA-DNA hybridization data. Strains that have at least 95.5% ITS sequence similarity belong to the same genospecies, i.e. they have more than 60% DNA-DNA hybridization values. The ITS sequences can therefore provide a relatively fast way to guide strain identification and aid selection of the reference groups that should be included in DNA-DNA hybridization experiments for precise genotypic identification. The Bradyrhizobium strains isolated from Aeschynomene species showed a much larger diversity in ITS sequences than other bradyrhizobia, possibly as a result of lateral exchange. The above ITS sequence similarity criterion for genospecies therefore does not apply to them, but they can easily be distinguished from other Bradyrhizobium genospecies because they have a distinct tRNA(ala) gene.
The suitability of a species identification technique based on PCR analysis of 16S-23S rRNA spacer region (SR) polymorphism for human intestinal Clostridium species was evaluated. This SR-PCR based technique is highly reproducible and successfully differentiated the strains tested, which included 17 ATCC type strains of Clostridium and 152 human stool Clostridium isolates, at the species or intraspecies level. Ninety-eight of 152 stool isolates, including C. bifermentans, C. butyricum, C. cadaveris, C. orbiscindens, C. paraputrificum, C. pefringens, C. ramosum, C. scindens, C. spiroforme, C. symbiosum and C. tertium, were identified to species level by SR-PCR patterns that were identical to those of their corresponding ATCC type strains. The other 54 stool isolates distributed among ten SR-PCR patterns that are unique and possibly represent ten novel Clostridium species or subspecies. The species identification obtained by SR-PCR pattern analysis completely agreed with that obtained by 16S rRNA sequencing, and led to identification that clearly differed from that obtained by cellular fatty acid analysis for 23/152 strains (15%). These results indicate that SR-PCR provides an accurate and rapid molecular method for the identification of human intestinal Clostridium species.
A PCR protocol was developed for the selective amplification of a segment of the ribosomal RNA operon in Pseudomonas strains. Two specific conserved sequences suitable for PCR priming were identified in the middle of the 16S rDNA and at the very beginning of the 23S rDNA respectively. As a result, amplified region includes the 3' half of the 16S rDNA with the whole 16S-23S rRNA Internal Transcripted Spacer (ITS1) sequence. The specificity of the primer set was checked on sequence databases and validated on collection strains and on one hundred soil bacterial isolates. Our results showed that both collection, soil-inhabiting Pseudomonas and some Pseudomonas-related Azotobacter DNAs could be amplified. This specific PCR for the detection of Pseudomonas strains was in good agreement with colony hybridisation using a Pseudomonas-specific probe. The targeted segment is relevant for a characterisation at the species (16S rDNA) as well as at the infraspecific (ITS1) levels. This PCR-based approach offers promising potential for the characterisation of environmental Pseudomonas populations.
Detection of catechol 2,3-dioxygenase genes in aromatic hydrocarbon contaminated environments gives the opportunity to measure the diversity of bacteria involved in the degradation of the contaminants under aerobic conditions. In this study, we investigated the diversity and distribution of Comamonadaceae family (Betaproteobacteria) related catechol 2,3-dioxygenase genes, which belong to the I.2.C subfamily of extradiol dioxygenase genes. These catabolic genes encode enzymes supposed to function under hypoxic conditions as well, and may play a notable role in BTEX degradation in oxygen limited environments. Therefore, their diversity was analyzed in oxygen limited, petroleum hydrocarbon contaminated groundwater by terminal restriction fragment length polymorphism and cloning. Subfamily I.2.C related catechol 2,3-dioxygenase genes were detected in every investigated groundwater sample and a dynamic change was observed in the case of the structure of C23O gene possessing bacterial communities. To link the metabolic capability to the microbial structure, 16S rRNA gene-based clone libraries were generated and it was concluded that Betaproteobacteria were abundant in the bacterial communities of the contaminated samples. These results support the opinion that Betaproteobacteria may play a significant role in BTEX degradation under hypoxic conditions.
Koalas are infected with two species of Chlamydia, C. pecorum and C. pneumoniae. While it is known that significant genetic diversity occurs in the C. pecorum strains infecting koalas, very little is known about the C. pneumoniae strains that infect this host. In the current study, 10 isolates of koala C. pneumoniae were analysed at four gene loci and found to be different to both the human and horse C. pneumoniae strains at all loci (biovar differences ranging from 0.3% at groESL up to 9.0% at ompAVD4). All koala biovar isolates studied were found to be 100% identical at ompAVD4 (all 10 isolates) and at ompB (all three isolates) gene. This lack of allelic polymorphisms at ompAVD4 has now been observed for koala C. pneumoniae, human C. pneumoniae, guinea pig inclusion conjuctivitis C. psittaci and feline conjuctivitis C. psittaci and may be correlated to a lack of antibody response to the chlamydial major outer membrane protein (MOMP) in these same strain/host combinations. This study also provides the first documented case of natural C. pneumoniae infection causing a severe and extended respiratory episode in a captive koala population. This captive episode is in contrast to most free-range observations in which koala C. pneumoniae is rarely documented as causing respiratory, ocular or urogenital tract disease.
Ribosomal rRNA gene fragments (rDNA) encompassing part of the 16S rDNA, the 16S-23S rDNA spacer region and part of the 23S rDNA of 229 Neisseria gonorrhoeae strains were enzymatically amplified using conserved primers. The fragments of approximately 1200 bp were subjected to restriction analysis with HinfI. This revealed 13 patterns (patterns I-XIII) of which patterns I (78 strains), II (32 strains), III (38 strains) and IV (56 strains) were the most abundant, comprising 89.1% of the strains. The obtained restriction patterns consisted of 3 to 8 bands, ranging in size from 32 to 854 bp. The sum of the obtained bands was about 1200 bp for patterns I, II, III, IV, V, IX, and XIII. However, for patterns VI, VII, VIII, X, XI and XII, the sum of the bands well exceeded the estimated size of approximately 1200 bp. We demonstrated that this results from sequence divergence in the 4 rRNA operons, present in the genome of N. gonorrhoeae, giving rise to patterns that are a combination of several other patterns.
One hundred and seventy three bacterial strains, isolated previously after enrichment under oligotrophic, psychrophylic conditions from Arctic (98 strains) and Antarctic seawater (75 strains), were characterized by gas-liquid chromatographic analysis of their fatty acid compositions. By numerical analysis, 8 clusters, containing 2 to 59 strains, could be delineated, and 8 strains formed separate branches. Five clusters contained strains from both poles, two minor clusters were confined to Arctic isolates, and one cluster consisted of Antarctic isolates only. The 16S rRNA genes from 23 strains, representing the different fatty acid profile clusters and including the unclustered strains, were sequenced. The sequences grouped with the alpha and gamma Proteobacteria, the high percent G+C gram positives, and the Cytophaga-Flavobacterium-Bacteroides branch. The sequences of strains from 4 clusters and of 7 unclustered strains were closely related (sequence similarities above 97%) to reference sequences of Sulfitobacter mediterraneus, Halomonas variabilis, Alteromonas macleodii, Pseudoalteromonas species, Shewanella frigidimarina, and Rhodococcus fascians. Strains from the other four clusters and an unclustered strain showed sequence similarities below 97% with nearest named neighbours, including Rhizobium, Glaciecola, Pseudomonas, Alteromonas macleodii and Cytophaga marinoflava, indicating that the clusters which they represent form as yet unnamed taxa.
StrainInfo has augmented its type strain and species/subspecies passports with a recommendation for a high-quality 16S rRNA gene sequence available from the public sequence databases. These recommendations are generated by an automated pipeline that collects all candidate 16S rRNA gene sequences for a prokaryotic type strain, filters out low-quality sequences and retains a high-quality sequence from the remaining pool. Due to thorough automation, recommendations can be renewed daily using the latest updates of the public sequence databases and the latest species descriptions. We discuss the quality criteria constructed to filter and rank available 16S rRNA gene sequences, and show how a partially ordered set (poset) ranking algorithm can be applied to solve the multi-criteria ranking problem of selecting the best candidate sequence. The proof of concept of the recommender system is validated by comparing the results of automated selection with an expert selection made in the All-Species Living Tree Project. Based on these validation results, the pipeline may reliably be applied for non-type strains and developed further for the automated selection of housekeeping genes.
The signing authors together with the journal Systematic and Applied Microbiology (SAM) have started an ambitious project that has been conceived to provide a useful tool especially for the scientific microbial taxonomist community. The aim of what we have called "The All-Species Living Tree" is to reconstruct a single 16S rRNA tree harboring all sequenced type strains of the hitherto classified species of Archaea and Bacteria. This tree is to be regularly updated by adding the species with validly published names that appear monthly in the Validation and Notification lists of the International Journal of Systematic and Evolutionary Microbiology. For this purpose, the SAM executive editors, together with the responsible teams of the ARB, SILVA, and LPSN projects (,, and, respectively), have prepared a 16S rRNA database containing over 6700 sequences, each of which represents a single type strain of a classified species up to 31 December 2007. The selection of sequences had to be undertaken manually due to a high error rate in the names and information fields provided for the publicly deposited entries. In addition, from among the often occurring multiple entries for a single type strain, the best-quality sequence was selected for the project. The living tree database that SAM now provides contains corrected entries and the best-quality sequences with a manually checked alignment. The tree reconstruction has been performed by using the maximum likelihood algorithm RAxML. The tree provided in the first release is a result of the calculation of a single dataset containing 9975 single entries, 6728 corresponding to type strain gene sequences, as well as 3247 additional high-fquality sequences to give robustness to the reconstruction. Trees are dynamic structures that change on the basis of the quality and availability of the data used for their calculation. Therefore, the addition of new type strain sequences in further subsequent releases may help to resolve certain branching orders that appear ambiguous in this first release. On the web sites: and, the All-Species Living Tree team will release a regularly updated database compatible with the ARB software environment containing the whole 16S rRNA dataset used to reconstruct "The All-Species Living Tree". As a result, the latest reconstructed phylogeny will be provided. In addition to the ARB file, a readable multi-FASTA universal sequence editor file with the complete alignment will be provided for those not using ARB. There is also a complete set of supplementary tables and figures illustrating the selection procedure and its outcome. It is expected that the All-Species Living Tree will help to improve future classification efforts by simplifying the selection of the correct type strain sequences. For queries, information updates, remarks on the dataset or tree reconstructions shown, a contact email address has been created ([email protected] /* */). This provides an entry point for anyone from the scientific community to provide additional input for the construction and improvement of the first tree compiling all sequenced type strains of all prokaryotic species for which names had been validly published.
31 different bacterial strains isolated using the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as the sole source of carbon, were investigated for their ability to mineralize 2,4-D and the related herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). Most of the strains mineralize 2,4-D considerably faster than MCPA. Three novel primer sets were developed enabling amplification of full-length coding sequences (CDS) of the three known tfdA gene classes known to be involved in phenoxy acid degradation. 16S rRNA genes were also sequenced; and in order to investigate possible linkage between tfdA gene classes and bacterial species, tfdA and 16S rRNA gene phylogeny was compared. Three distinctly different classes of tfdA genes were observed, with class I tfdA sequences further partitioned into the two sub-classes I-a and I-b based on more subtle differences. Comparison of phylogenies derived from 16S rRNA gene sequences and tfdA gene sequences revealed that most class II tfdA genes were encoded by Burkholderia sp., while class I-a, I-b and III genes were found in a more diverse array of bacteria.
Top-cited authors
Karl H Schleifer
  • Technische Universität München
Michael Wagner
  • University of Vienna
Erko Stackebrandt
  • Leibniz Institut DSMZ - Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH
Jean Swings
  • Ghent University
Mike S M Jetten
  • Radboud University