Applied and environmental microbiology (Appl Environ Microbiol)

Publications in this journal

• Article: Analysis of trans-kingdom genetic transfer from Escherichia coli to Saccharomyces cerevisiae as a simple gene introduction tool.

  Kazuki Moriguchi, Noritaka Edahiro, Shinji Yamamoto, Katsuyuki Tanaka, Nori Kurata, Katsunori Suzuki
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  ABSTRACT: Trans-kingdom conjugation (TKC) permits transfer of DNA from bacteria to eukaryotic cells using a bacterial conjugal transfer system. However, it is not clear whether the process of DNA acceptance in a recipient eukaryote is homologous to the process of conjugation between bacteria. TKC transfer requires mobilizable shuttle vectors that are capable of conjugal transfer and replication in the donor and the recipient strains. Here we developed TKC vectors derived from plasmids belonging to the IncP and IncQ groups. We also investigated forms of transfer of these vectors from Escherichia coli into Saccharomyces cerevisiae to develop TKC as a simple gene introduction method. Both types of vectors were transferred precisely conserving the origin of transfer (oriT) sequences, but IncP-based vectors appeared to be more efficient than an IncQ-based vector. Interestingly, unlike in agrobacterial T-DNA transfer, the efficiency of TKC transfer was similar between a wild type yeast strain and DNA repair mutants defective in homologous recombination (rad51Δ and rad52Δ) or non-homologous end joining (rad50Δ, yku70Δ and lig4Δ). Lastly, a shuttle vector with two repeats of oriT(P) sequences flanking a marker gene was constructed. TKC transfer of this vector resulted in precise excision of both the oriT(P) loci as well as the marker gene, albeit at a low frequency of 17% of all transconjugants. This feature would be attractive in biotechnological applications of TKC. Taken together these results strongly suggest that in contrast to agrobacterial T-DNA transfer, the circularization of vector ssDNA may occur either before or after transfer, but requires factor(s) from the donor. TKC is a simple method of gene transfer with possible applications in yeast genetics and biotechnology.
  Applied and environmental microbiology 05/2013;
• Article: Characterization of a novel DyP-type peroxidase from Irpex lacteus and its application in the enzymatic hydrolysis of wheat straw.

  Davinia Salvachúa, Alicia Prieto, Angel T Martínez, María Jesús Martínez
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  ABSTRACT: Irpex lacteus is a white-rot basidiomycete proposed for a wide spectrum of biotechnological applications which presents an interesting, but still scarcely known, enzymatic oxidative system. Among these enzymes, the production, purification, and identification of a new dye-decolorizing peroxidase (DyP)-type enzyme, as well as its physico-chemical, spectroscopic, and catalytic properties, are described in the current work. According to its N-terminal sequence and peptide mass fingerprinting analyses, I. lacteus DyP showed high homology (>95%) with the hypothetical (nor isolated either characterized) protein cpop21, from an unidentified species of the family Polyporaceae. The enzyme had a low optimal pH (2-4), was very stable to acid pH and temperature, and showed improved activity and stability at high H2O2 concentrations compared to other peroxidases. Other attractive features of I. lacteus DyP were its high catalytic efficiency oxidizing the recalcitrant anthraquinone and azo-dyes assayed (kcat/Km = 1.6 × 10(6) s(-1) M(-1)), and its ability of oxidizing non-phenolic aromatic compounds like veratryl alcohol. In addition, the effect of this DyP during the enzymatic hydrolysis of wheat straw was checked. The results suggest that I. lacteus DyP displayed a synergistic action with cellulases during the hydrolysis of wheat straw, increasing significantly the fermentable glucose recoveries from this substrate. These results show a promising biotechnological potential for this enzyme.
  Applied and environmental microbiology 05/2013;
• Article: Generic Escherichia coli contamination of spinach at the preharvest level: The role of farm management and environmental factors.

  Sangshin Park, Sarah Navratil, Ashley Gregory, Arin Bauer, Indumathi Srinath, Mikyoung Jun, Barbara Szonyi, Kendra Nightingale, Juan Anciso, Renata Ivanek
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  ABSTRACT: The objective of this study was to determine the effect of farm management and environmental factors on preharvest spinach contamination with generic Escherichia coli as an indicator of fecal contamination. A repeated cross-sectional study was conducted by visiting spinach farms up to four times per growing season over a period of two years (2010-2011). Spinach samples (n = 955) were collected from 12 spinach farms in Colorado and Texas as representative states of the Western and Southwestern United States, respectively. During each farm visit, farmers were surveyed about farm-related management and environmental factors using a questionnaire. Associations between the prevalence of generic E. coli in spinach and farm-related factors were assessed using a multivariable logistic regression model including random effects for farm and farm visit. Overall, 6.6% of spinach samples were positive for generic E. coli. Significant risk factors for spinach contamination with generic E. coli were the proximity (within 10 miles) of a poultry farm, the use of pond water for irrigation, a > 66 day period since planting spinach, farming on fields previously used for grazing, the production of hay before spinach planting, and the farm location in the Southwestern United States. Contamination with generic E. coli was significantly reduced with an irrigation lapse time > 5 days, as well as by several factors related to field workers including the use of portable toilets, training to use portable toilets, and the use of hand-washing stations. To our knowledge, this is the first report of an association between field workers' personal hygiene and produce contamination with generic E. coli at the preharvest level. Collectively, our findings support that practice of good personal hygiene and other good farm-management practices may reduce produce contamination with generic E. coli at the preharvest level.
  Applied and environmental microbiology 05/2013;
• Article: Genetic variability of vancomycin-resistant Enterococcus faecium and Enterococcus faecalis isolated from humans, chickens and pigs in Malaysia.

  Yitbarek Getachew, Latiffah Hassan, Zunita Zakaria, Saleha A Aziz
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  ABSTRACT: Vancomycin-resistant enterococci (VRE) have been reported to be present in humans, chickens and pigs in Malaysia. In the present study, representative samples of VRE isolated from these populations were examined similarities and differences using the multilocus sequence typing (MLST) method. Housekeeping genes of Enterococcus faecium (n=14) and Enterococcus faecalis (n=11) isolates were sequenced and analyzed using MLST database, eBURST and goeBURST. We found five sequence types (STs) of E. faecium and six STs of E. faecalis existing in Malaysia. Enterococcus faecium of ST203, ST17, ST55, ST79 and ST29 were identified and E. faecium ST203 was the most common among humans. The MLST profiles of E. faecium from humans in this study were similar to the globally reported nosocomial-related strain lineage belonging to clonal complex (CC) 17. Isolates from chickens and pigs have little similarities to those of humans except for one isolate from a chicken, which was identified as ST203. E. faecalis were more diverse and were identified as ST4, ST6, ST87, ST108, ST274 and ST244, which were grouped as specific to the three hosts. E. faecalis, belonging to the high-risk CC2 and CC87, were detected among isolates from humans. In conclusion, even though one isolate in chicken was found clonal to that of humans, the MLST analysis of E. faecium and E. faecalis supports the findings of others who suggest VRE to be predominantly host-specific and that clinically important strains are mainly found among humans. The infrequent detection of human VRE clone in a chicken may in fact suggest a reverse transmission of VRE from humans to animals.
  Applied and environmental microbiology 05/2013;
• Article: Arsenic bioremediation by biogenic iron oxides and sulfides.

  Enoma O Omoregie, Raoul-Marie Couture, Philippe Van Cappellen, Claire L Corkhill, John M Charnock, David A Polya, David Vaughan, Karolien Vanbroekhoven, Jonathan R Lloyd
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  ABSTRACT: Microcosms containing sediment from an aquifer in Cambodia with naturally elevated levels of arsenic (As) in the associated groundwater were used to evaluate the effectiveness of microbially-mediated production of iron minerals for in situ As remediation. The microcosms were first incubated without amendments for 28 days and the release of As and other geogenic chemicals from the sediments into the aqueous phase was monitored. Nitrate, or a mixture of sulfate and lactate, was then added to stimulate biological Fe(II) oxidation or sulfate reduction, respectively. Without treatment soluble As concentrations reached 3.9 (±0.9) μM at the end of the 143 day experiment. However, in the nitrate and sulfate plus lactate amended microcosms, soluble As levels decreased to 0.01 and 0.41(±0.13) μM, respectively, by the end of the experiment. Analyses using a range of biogeochemical and mineralogical tools, indicated that sorption onto freshly formed hydrous ferric oxide (HFO) and iron sulfide mineral phases are the likely mechanisms for As removal in the respective treatments. Incorporation of the experimental results into a one-dimensional transport-reaction model suggests that, under conditions representative of the Cambodian aquifer, the in situ precipitation of HFO would be effective in bringing groundwater into compliance with the World Health Organization (WHO) provisional guideline value for As (10 ppb or 0.13 μM), although soluble Mn release accompanying microbial Fe(II) oxidation presents a potential health concern. In contrast, production of biogenic iron sulfide minerals would not remediate the groundwater As concentration below the recommended WHO limit.
  Applied and environmental microbiology 05/2013;
• Article: Exploring Mechanisms of Intracellular P Heterogeneity in Cultured Phytoplankton using Agent Based Modeling.

  Neil D Fredrick, John A Berges, Benjamin S Twining, Daliangelis Nuñez-Milland, Ferdi L Hellweger
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  ABSTRACT: There can be significant intraspecific individual-level heterogeneity in the intracellular P of phytoplankton, which can affect the population-level growth rate. Several mechanisms can create this heterogeneity, including phenotypic variability in various physiological functions (e.g., nutrient uptake rate). Here we use modeling to explore the contribution of various mechanisms to the heterogeneity in phytoplankton grown in a laboratory culture. An agent-based model simulates individual cells and their intracellular P. Heterogeneity is introduced by randomizing parameters (e.g., maximum uptake rate) of daughter cells at division. The model was calibrated to observations of P quota of individual cells of the centric diatom Thalassiosira pseudonana obtained using synchrotron X-ray fluorescence (SXRF). Then, a number of simulations with individual mechanisms of heterogeneity turned off were performed. Comparison of the coefficient of variation (CV) of these and the baseline simulation (all mechanisms turned on) provides an estimate of the relative contribution of these mechanisms. The results show that the mechanism with the largest contribution is variability in the parameter characterizing the maximum intracellular P, which when removed results in a CV of 0.21 compared to a CV of 0.37 with all mechanisms turned on. This suggests that nutrient/element storage capabilities/mechanisms are important determinants of intrapopulation heterogeneity.
  Applied and environmental microbiology 05/2013;
• Article: ProP is required for the survival of desiccated Salmonella Typhimurium on a stainless steel surface.

  Sarah Finn, Kristian Händler, Orla Condell, Aoife Colgan, Shane Cooney, P McClure, A Amézquita, Jay C D Hinton, Séamus Fanning
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  ABSTRACT: Consumers trust commercial food production to be safe, and it is important to strive to improve food safety at every level. Several food-borne outbreaks of disease have been caused by Salmonella associated with dried food. Currently we do not know the mechanisms used by Salmonella enterica serovar Typhimurium to survive in desiccated environments. The aim of this study was to discover the response of S. Typhimurium ST4/74 to desiccation on a stainless steel surfaces at the transcriptional level, and to subsequent rehydration. Bacterial cells were dried onto the same steel surfaces used during production of dry foods, and RNA was recovered for transcriptomic analysis. Subsequently, dried cells were rehydrated and again used for transcriptomic analysis. A total of 266 genes were differentially expressed under desiccation stress, compared with a static broth culture. The osmoprotectant transporters proP, proU and osmU (STM1491-94) were highly up-regulated by drying. Deletion of any one of these transport systems resulted in a reduction in the long term viability of S. Typhimurium on a stainless steel food contact surface. The proP gene was critical for survival, as proP deletion mutants could not survive for long periods of desiccation and were undetectable after 4 weeks. Following rehydration, 138 genes were differentially expressed, with up-regulation observed in genes such as proP, proU and phosphate transport (pstACS). In time, this knowledge should prove valuable in understanding the underlying mechanisms involved in pathogen survival and lead to improved methods for control to assure the safety of intermediate and low moisture foods.
  Applied and environmental microbiology 05/2013;
• Article: An MSH4 homolog, stpp1, from Pleurotus pulmonarius is a silver bullet to solve spore-caused problems in cultivated mushrooms.

  Yasuhito Okuda, Shigeyuki Murakami, Yoichi Honda, Teruyuki Matsumoto
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  ABSTRACT: The enormous number of spores produced by fruiting bodies during cultivation of mushrooms can lead to allergic reactions of workers, reduction of commercial value, spread of mushroom disease, pollution of facilities, and depletion of genetic diversity in natural populations. A cultivar harboring a sporulation-deficient (sporeless) mutation would be very useful for preventing these problems, but sporeless commercial cultivars are very limited because sporeless traits are often linked with traits that are unfavorable for commercial cultivation. Thus, identifying a causal gene of sporeless unlinked to the adverse traits in breeding and cultivation is crucial for the establishment of sporeless breeding using a Targeting Induced Local Lesions IN Genomes (TILLING) strategy in cultivated mushrooms. We used a Pleurotus pulmonarius (Fr.) Quél. sporeless strain to identify and characterize the single recessive gene controlling the mutation. The 3,853 bp stpp1 gene encodes a protein of 854 amino acids and belongs to the MutS homolog (MSH) family associated with mismatch repair in DNA synthesis or recombination in meiosis. Gene expression analysis of the fruiting body showed that this gene is strongly expressed in the gills. Phenotypic analysis of disruptants formed by gene targeting suggested a reproducible sporeless phenotype. Mutants deficient in a functional copy of this gene have no unfavorable traits for sporeless cultivar breeding, so this gene will be an extremely useful target for efficient and versatile sporeless breeding in P. pulmonarius and various other cultivated mushrooms.
  Applied and environmental microbiology 05/2013;
• Article: A Universally Applicable and Rapid Method for Measuring Growth of Streptomyces and Other Filamentous Microorganisms by Methylene Blue Adsorption/Desorption.

  Marco Fischer, R Gary Sawers
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  ABSTRACT: Quantitative assessment of growth of filamentous microorganisms, such as streptomycetes, is generally restricted to determination of dry weight. Here, we describe a straightforward methylene blue-based sorption assay to monitor microbial growth quantitatively, simply and rapidly. The assay is equally applicable to unicellular as well as filamentous bacterial and eukaryotic microorganisms.
  Applied and environmental microbiology 05/2013;
• Article: Occurrence of the transferable copper resistance gene, tcrB, among fecal enterococci of U.S. feedlot cattle fed copper-supplemented diets.

  R G Amachawadi, H M Scott, C A Alvarado, T R Mainini, J Vinasco, J S Drouillard, T G Nagaraja
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  ABSTRACT: Copper, an essential micronutrient, is supplemented in the diet at elevated levels to reduce morbidity and mortality and to promote growth in feedlot cattle. Gut bacteria exposed to copper can acquire resistance, which among enterococci is conferred by a transferable copper resistance gene (tcrB) borne on a plasmid. The present study was undertaken to investigate whether the feeding of copper at levels sufficient to promote growth increases the prevalence of the tcrB gene among the fecal enterococci of feedlot cattle. The study was performed with 261 crossbred yearling heifers housed in 24 pens, with pens assigned randomly to a 2×2 factorial arrangement of treatments consisting of dietary copper and a commercial linseed meal-based energy protein supplement. A total of 22 isolates, each identified as E. faecium, were positive for tcrB with an overall prevalence of 3.8% (22/576). The prevalence was higher among the cattle fed diets supplemented with copper (6.9%) compared to normal copper (0.7%). The tcrB-positive isolates always contained both erm(B) and tet(M) genes. Median copper MICs for tcrB-positive and tcrB-negative enterococci were 22 mM and 4 mM, respectively. The transferability of the tcrB gene was demonstrated via a filter mating assay. Multi-locus variable number tandem repeat analysis revealed a genetically diverse population of enterococci. The finding of a strong association between the copper resistance gene and other antibiotic (tetracycline and tylosin) resistance determinants is significant because enterococci remain potential pathogens and have the propensity to transfer resistance genes to other bacteria in the gut.
  Applied and environmental microbiology 05/2013;
• Article: Malonate catabolism does not drive N2-fixation in legume nodules.

  Ramakrishnan Karunakaran, Alison K East, Philip S Poole
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  ABSTRACT: Malonyl-CoA decarboxylase, malonyl-CoA synthetase and malonate transporter mutants of Rhizobium leguminosarum biovars viciae and trifolii fixed N2 at wild type rates on pea and clover respectively. Thus malonate does not drive N2-fixation in legume nodules.
  Applied and environmental microbiology 05/2013;
• Article: Molecular analysis of lactococcal phages Q33 and BM13: Identification of a new P335 subgroup.

  Jennifer Mahony, Bruno Martel, Denise M Tremblay, Horst Neve, Knut J Heller, Sylvain Moineau, Douwe van Sinderen
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  ABSTRACT: Lactococcal dairy starter strains are under constant threat from phages in dairy fermentation facilities, especially by members of the so-called 936, P335, and c2 species. Among these three phage groups, members of the P335 species represent the most genetically diverse. Here we present the complete genome sequence of two P335-type phages, Q33 and BM13, isolated in North America and representing a novel lineage within this phage group. The Q33 and BM13 genomes exhibit homology not only to P335-type, but also elements of the 936-type phage sequences. These two phage genomes also have close relatedness to phages infecting Enterococcus and Clostridium, a heretofore unknown feature among lactococcal P335 phages. The Q33 and BM13 genomes are organised in functionally related clusters with genes encoding functions such as DNA replication and packaging, morphogenesis and host cell lysis. Electron micrographic analysis of the two phages highlights the presence of a baseplate being more reminiscent of the baseplate of 936 phages than that the majority of members of the P335 group, with the exception of r1t and LC3.
  Applied and environmental microbiology 05/2013;
• Article: Environmental dissolved organic matter governs biofilm formation and subsequent linuron-degrading activity of a linuron-degrading bacterial consortium.

  Benjamin Horemans, Philip Breugelmans, Johan Hofkens, Erik Smolders, Dirk Springael
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  ABSTRACT: It was examined whether biofilm growth on dissolved organic matter (DOM) of a three-species consortium whose members synergistically degrade the phenylurea herbicide linuron, affected the consortium's integrity and subsequent linuron-degrading functionality. Citrate as a model DOM as well as three environmental DOM (eDOM) of different quality were used. Biofilms developed with all DOM formulations and the three species were retained in the biofilm. However, biofilm biomass, species composition, architecture and co-localization of member strains depended on DOM and its biodegradability. To assess the linuron-degrading functionality, biofilms were subsequently irrigated with linuron at 10 mg L(-1) or 100 μg L(-1). Instant linuron degradation, the time needed to attain maximal linuron degradation and hence the total amount of linuron removed depended on both the DOM used for growth and the linuron concentration. At 10 mg L(-1), final linuron degradation efficiency was as high as previously observed without DOM except for biofilms fed with humic acids which did not degrade linuron. At 100 μg L(-1) linuron, DOM grown biofilms degraded linuron less efficient than without DOM. The amount of linuron removed was more correlated with biofilm species composition than with biomass or structure. Based on visual observations, co-localization of consortium members in biofilms after the DOM feed appears essential for instant linuron-degrading activity and might explain the differences in overall linuron degradation. The data show that DOM quality determines biofilm structure and composition of the pesticide-degrading consortium in periods with DOM as main C-source and can affect subsequent pesticide-degrading activity; especially at micropollutant concentrations.
  Applied and environmental microbiology 05/2013;
• Article: Zirex: a novel Zinc-regulated expression system for Lactococcus lactis.

  Dongdong Mu, Manuel Montalbán-López, Yoshimitsu Masuda, Oscar P Kuipers
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  ABSTRACT: Here we report a new zinc-inducible expression system for Lactococcus lactis consisting of the pneumococcal repressor SczA and PczcD. PczcD tightly regulates the expression of GFP in L. lactis. We show the applicability of PczcD together with the nisin-inducible expression system, enabling simultaneous but independent regulation of different genes.
  Applied and environmental microbiology 05/2013;
• Article: Garvicin A, a Novel Class IId Bacteriocin from Lactococcus garvieae that Inhibits Septum Formation in L. garvieae Strains.

  Antonio Maldonado-Barragán, Nivia Cárdenas, Beatriz Martínez, José Luis Ruiz-Barba, José F Fernández-Garayzábal, Juan M Rodríguez, Alicia Gibello
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  ABSTRACT: Lactococcus garvieae 21881, isolated from a human clinical case, produces a novel class IId bacteriocin, garvicin A (GarA), which is specifically active against other L. garvieae strains, including fish and bovine pathogenic isolates. Purification from active supernatants, sequence analyses, and plasmid-curing experiments identified pGL5, one of the five plasmids found in L. garvieae 21881 (Aguado-Urda M, Gibello A, Blanco MM, López-Campos GH, Cutuli MT, Fernández-Garayzábal JF. 2012. PLoS ONE 7 (6):e40119. doi:10.1371/journal.pone.0040119), as the coding plasmid for the structural gene of GarA (lgnA), its putative immunity protein (lgnI), and the ABC-transporter and its accessory protein (lgnC and lgnD). Interestingly, pGL5-cured strains were still resistant to GarA. Other putative bacteriocins encoded by the remaining plasmids were not detected during purification pointing to GarA as the main inhibitor secreted by L. garvieae 21881. Mode of action studies revealed a potent bactericidal activity of GarA. Moreover, transmission microscopy showed that GarA seems to act by inhibiting septum formation in L. garvieae cells. The potent and species-specific inhibition by GarA anticipates promising applications for the prevention or treatment of infections caused by pathogenic strains of L. garvieae in both veterinary and clinical settings.
  Applied and environmental microbiology 05/2013;
• Article: Adaptation of hydrocarbonoclastic Alcanivorax borkumensis SK2 to alkanes and toxic organic compounds - a physiological and transcriptomic approach.

  Daniela J Naether, Slavtscho Slawtschew, Sebastian Stasik, Maria Engel, Martin Olzog, Lukas Y Wick, Kenneth N Timmis, Hermann J Heipieper
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  ABSTRACT: The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is able to degrade mixtures of n-alkanes as they occur in marine oil spills. However, investigations on growth behavior and physiology of these bacteria cultivated with n-alkanes of different chain lengths (C6-C30) as substrates are still missing. Growth rates increased with increasing alkane chain length up to a maximum between C12 and C19, with no evident difference between even and odd numbered chain lengths, before decreasing with chain length greater than C19. Surface hydrophobicity of alkane-grown cells, assessed by determination of the water contact angles, showed a similar pattern with maximum values associated with growth rates on alkanes with chain lengths between C11 and C19, and was significantly lower for cells grown on pyruvate. A. borkumensis was found to incorporate and modify the fatty acid intermediates generated by the corresponding n-alkane degradation pathway. Cells grown on distinct n-alkanes proved the capability to not only incorporate but also modify fatty intermediates derived from the alkane degradation pathway. Comparing cells grown on pyruvate with those cultivated on hexadecane regarding their tolerance towards two groups of toxic organic compounds (chlorophenols and alkanols) representing intensely studied organic compounds revealed similar tolerances towards chlorophenols, whereas toxicity of different n-alkanols was significantly reduced when hexadecane was used as carbon source. As one adaptive mechanism of A. borkumensis to these toxic organic solvents the activity of cis-trans isomerisation of unsaturated fatty acids was proven. These findings could be verified by a detailed transcriptomic comparison between cultures grown on hexadecane and pyruvate including solvent stress caused by addition of 1-octanol as the most toxic intermediate of n-alkane degradation.
  Applied and environmental microbiology 05/2013;
• Article: Comparative genomics of Bifidobacterium animalis subsp. lactis reveals a strict monophyletic bifidobacterial taxon.

  Christian Milani, Sabrina Duranti, Gabriele Andrea Lugli, Francesca Bottacini, Francesco Strati, Stefania Arioli, Elena Foroni, Francesca Turroni, Douwe van Sinderen, Marco Ventura
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  ABSTRACT: Strains of Bifidobacterium animalis subsp. lactis are extensively exploited by the food industry as health-promoting bacteria, although the genetic variability of members belonging to this taxon has so far not received much scientific attention. In this manuscript we describe the complete genetic make-up of the B. animalis subsp. lactis Bl12 genome and discuss its genetic relatedness with other so far sequenced strains belonging to this taxon. Moreover, a detailed comparative genomic analysis of B. animalis subsp. lactis genomes was performed, which revealed a closely related and isogenic nature of all currently available B. animalis subsp. lactis strains, thus strongly suggesting a closed pan-genome structure of this bacterial group.
  Applied and environmental microbiology 05/2013;
• Article: Characterization of a novel Rickettsiella in the leafhopper Orosius albicinctus (Hemiptera: Cicadellidae).

  Lilach Iasur-Kruh, Phyllis G Weintraub, Netta Mozes-Daube, Wyatt E Robinson, Steve J Perlman, Einat Zchori-Fein
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  ABSTRACT: Bacteria in the genus Rickettsiella (Coxiellaceae), which are mainly known as arthropod pathogens, are emerging as excellent models to study transitions between mutualism and pathogenicity. The current study characterizes a novel Rickettsiella found in the leafhopper Orosius albicinctus (Hemiptera: Cicadellidae), a major vector of phytoplasma diseases in Europe and Asia. DGGE and pyrosequencing were used to survey the main symbionts of O. albicinctus, revealing the obligate symbionts Sulcia and Nasuia, and the facultative symbionts Arsenophonus and Wolbachia, in addition to Rickettsiella. The leafhopper Rickettsiella is allied with strains found in ticks. Screening O. albicinctus in the field showed that Rickettsiella is highly prevalent, with over 60% of individuals infected. A stable Rickettsiella infection was maintained in a leafhopper laboratory colony for at least 10 generations, and flourescence microscopy localized bacteria to accessory glands of the female reproductive tract, suggesting that the bacterium is vertically transmitted. Future studies will be needed to examine how Rickettsiella affects host fitess and its ability to vector phytopathogens.
  Applied and environmental microbiology 05/2013;
• Article: Insights into the structure and metabolic function of microbes that shape pelagic iron-rich aggregates (iron snow).

  Shipeng Lu, Karuna Chourey, Marco Reiche, Sandor Nietzsche, Manesh B Shah, Thomas R Neu, Robert L Hettich, Kirsten Küsel
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  ABSTRACT: Microbial ferrous iron (Fe(II)) oxidation leads to the formation of iron-rich macroscopic aggregates (iron snow) at the redoxcline in a stratified lignite mine lake in east-central Germany. We aimed to identify the abundant Fe-oxidizing and Fe-reducing microorganisms likely to be involved in the formation and transformation of iron snow present in the redoxcline in two basins of the lake differing in their pH. Nucleic acid- and lipid-stained microbial cells of various morphologies detected by confocal laser scanning microscopy were homogeneously distributed in all iron snow samples.The dominant iron mineral appeared to be schwertmannite with shorter needles in the northern compared to central basin samples. Total bacterial 16S rRNA gene copies ranged from 5.0 × 10(8) copies g (dry wt)(-1) in the acidic central lake basin (pH 3.3) to 4.0 × 10(10) copies g (dry wt)(-1) in the less acidic (pH 5.9) northern basin. Total RNA-based quantitative PCR assigned up to 61% of metabolically active microbial communities to Fe-oxidizing- and Fe-reducing-related bacteria, indicating that iron metabolism was an important metabolic strategy. Molecular identification of abundant groups suggested that iron snow surfaces were formed by chemoautotrophic iron oxidizers, such as Acidimicrobium, Ferrovum, Acidithiobacillus, Thiobacillus and Chlorobium in the redoxcline, and were rapidly colonized by heterotrophic iron reducers, such as Acidiphilium, Albidiferax-like and Geobacter-like groups. Metaproteomics yielded 283 different proteins from northern basin iron snow samples, and protein identification provided a glimpse into some of their in situ metabolic processes, such as primary production (CO2 fixation), respiration, motility and survival strategies.
  Applied and environmental microbiology 05/2013;