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Bacterium
Kinds of Bacterium Terms modified by Bacterium Selected AbstractsStructural Determination of the O-Chain Polysaccharide from the Lipopolysaccharide of the Haloalkaliphilic Halomonas pantelleriensis Bacterium,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2006M. Michela Corsaro Abstract The structural determination of the O-chain repeating unit of the lipopolysaccharide from the haloalkaliphilic Halomonas pantelleriensis bacterium is described. The structure of the repeating unit was suggested on the basis of chemical analysis and NMR and MS data. The 4- O -[(S)-1-carboxyethyl]- D -GlcA residue has been found for the first time in a lipopolysaccharide, being previously only found in capsular polysaccharides. A comparison of the O-chain structures of Halomonas magadiensis and H. pantelleriensis is also reported. The results show that both bacteria present lipopolysaccharides containing a high number of carboxylate groups whose salification might determine a protective buffer effect on bacterium against extreme life conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Infection with the Intracellular Bacterium, Listeria monocytogenes, Overrides Established Tolerance in a Mouse Cardiac Allograft ModelAMERICAN JOURNAL OF TRANSPLANTATION, Issue 7 2010T. Wang Infections and TLR signals at the time of transplantation have been shown to prevent the induction of tolerance, but their effect on allografts after tolerance has been established is unclear. We here report that infection with Listeria monocytogenes precipitated the loss of tolerance and the MyD88- and T cell-dependent rejection of accepted cardiac allografts in mice. This loss of tolerance was associated with increases in the numbers of graft-infiltrating macrophages and dendritic cells, as well as CD4+FoxP3, and CD8+ T cells. Rejection was also associated with increased numbers of graft-infiltrating alloreactive as well as Listeria-reactive IFN,-producing T cells. Rejection of the established grafts required both IL-6 and IFNß, cytokines produced during acute Listeria infection. However, IL-6 and IFNß alone, even when present at higher concentrations than during Listeria infection, were insufficient to break tolerance, while the combination of IL-6 and IFNß was sufficient to break tolerance. These and in vitro observations that IL-6 but not IFNß enhanced T cell proliferation while IFNß but not IL-6 enhanced IFN, production support a hypothesis that these cytokines play nonredundant roles. In conclusion, these studies demonstrate that the proinflammatory effects of infections can induce the loss of tolerance and acute rejection of accepted allografts. [source] Biological Iron-Monosulfide Production for Efficient Electricity Harvesting from a Deep-Sea Metal-Reducing BacteriumCHEMBIOCHEM, Issue 5 2010Ryuhei Nakamura Dr. FeS source: A metal-reducing bacterium, Shewanella loihica PV-4, has evolved the ability to utilize Fe 3d electrons from biogenic FeS as a long-distance electron-transfer conduit. Self-organizing, electron-conducting cellular networks enable the generation of a microbial current two orders of magnitude higher than in cell cultures lacking the biogenic minerals. [source] Cervimycin A,D: A Polyketide Glycoside Complex from a Cave Bacterium Can Defeat Vancomycin ResistanceCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2005Kerstin Herold Dr. Abstract Cervimycins A,D are novel polyketide glycosides with significant activity against multi-drug-resistant staphylococci and vancomycin-resistant enterococci. They are produced by a strain of Streptomyces tendae, isolated from an ancient cave. The structures of the cervimycins were determined by performing extensive NMR and chemical degradation studies. All cervimycins have a common tetracyclic polyketide core that is substituted with unusual di- and tetrasaccharide chains, composed exclusively of trideoxysugars; however, they differ in the acetyl and carbamoyl ring substituent and in the highly unusual terminal methylmalonyl and dimethylmalonyl residues. [source] Colon Carcinoma- Bugs, Bacterium and Bone MarrowCOLORECTAL DISEASE, Issue 3 2010Marc Winslet No abstract is available for this article. [source] Quantification of Shigella IcsA required for bacterial actin polymerizationCYTOSKELETON, Issue 4 2002Juana Magdalena Abstract Shigella move through the cytoplasm of host cells by active polymerization of host actin to form an "actin tail." Actin tail assembly is mediated by the Shigella protein IcsA. The process of Shigella actin assembly has been studied extensively using IcsA-expressing Escherichia coli in cytoplasmic extracts of Xenopus eggs. However, for reasons that have been unclear, wild type Shigella does not assemble actin in these extracts. We show that the defect in actin assembly in Xenopus extracts by Shigella can be rescued by increasing IcsA expression by approximately 3-fold. We calculate that the number of IcsA molecules required on an individual bacterium to assemble actin filaments in extracts is approximately 1,500,2,100 molecules, and the number of IcsA molecules required to assemble an actin tail is approximately 4,000 molecules. The majority of wild type Shigella do not express these levels of IcsA when grown in vitro. However, in infected host cells, IcsA expression is increased 3.2-fold, such that the number of IcsA molecules on a significant percentage of intracellular wild type Shigella would exceed that required for actin assembly in extracts. Thus, the number of IcsA molecules estimated from our studies in extracts as being required on an individual bacterium to assemble actin filaments or an actin tail is a reasonable prediction of the numbers required for these functions in Shigella -infected cells. Cell Motil. Cytoskeleton 51:187,196, 2002. © 2002 Wiley-Liss, Inc. [source] The significance of a facultative bacterium to natural populations of the pea aphid Acyrthosiphon pisumECOLOGICAL ENTOMOLOGY, Issue 2 2003A. C. Darby Abstract. 1., Laboratory studies have implicated various accessory bacteria of aphids as important determinants of aphid performance, especially on certain plant species and under certain thermal regimes. One of these accessory bacteria is PABS (also known as T-type), which is distributed widely but is not universal in natural populations of the pea aphid Acyrthosiphon pisum in the U.K. 2., To explore the impact of PABS on the performance of A. pisum , the nymphal development time and fecundity of aphids collected directly from natural populations and caged on the host plant Vicia faba in the field were quantified. Over 4 consecutive months June,September 1999, the performance of PABS-positive and PABS-negative aphids did not differ significantly. 3., Deterministic modelling of the performance data showed that the variation in simulated population increase of PABS-positive and PABS-negative aphids would overlap substantially. 4., Analysis of aphids colonising five host plants ( Lathyrus odoratus , Medicago sativa , Pisum sativum , Trifolium pratense , Vicia faba ) between April and September 2000 and 2001, identified no robust differences between the distribution of PABS-positive and PABS-negative aphids on different plants and with season or temperature. 5., It is concluded that PABS is not an important factor shaping the performance or plant range of A. pisum under the field conditions tested. Reasons for the discrepancies between this study and laboratory-based studies are considered. [source] Extraordinarily widespread and fantastically complex: comparative biology of endosymbiotic bacterial and fungal mutualists of insectsECOLOGY LETTERS, Issue 2 2010Cara M. Gibson Ecology Letters (2010) 13: 223,234 Abstract Endosymbiosis is a pervasive, powerful force in arthropod evolution. In the recent literature, bacterial symbionts of insects have been shown to function as reproductive manipulators, nutritional mutualists and as defenders of their hosts. Fungi, like bacteria, are also frequently associated with insects. Initial estimates suggest that insect,fungal endosymbionts are hyperdiverse, yet there has been comparatively little research investigating the roles that fungi play in their insect hosts. In many systems in which the bacterial symbionts are well-characterized, the possible presence of fungi has been routinely ignored. Why has there been so little research on this important group of symbionts? Here, we explore the differences between fungal and bacterial endosymbiotic insect mutualists. We make predictions about why a bacterium or fungus might be found associated with an insect host given particular ecological, physiological, or evolutionary conditions. We also touch on the various hurdles for studying fungal vs. bacterial endosymbionts and potential future research directions. [source] Rapid detection of Staphylococcus aureus by a combination of monoclonal antibody-coated latex and capillary electrophoresisELECTROPHORESIS, Issue 9 2006Peng Gao Abstract The rapid detection of pathogenic bacteria is extremely important in biotechnology and clinical diagnosis. CE has been utilized in the field of bacterial analysis for many years, but to some extent, simultaneous separation and identification of certain microbes from complex samples by CE coupled with UV detector is still a challenge. In this paper, we propose a new strategy for rapid separation and identification of Staphylococcus aureus (S.,aureus) in bacterial mixtures by means of specific mAb-coated latex coupled with CZE. An appropriate set of conditions that selectively isolated S.,aureus from the microorganisms Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae were established. S.,aureus could be differentiated from the others by unique peaks in the electropherograms. The validity was also confirmed by LIF with antibodies specific to both the latex and the microbial cells. The LOD is as low as 9.0×105 colony forming unit/mL. We have also utilized this technology to identify S.,aureus in a stool sample coming from a healthy volunteer spiked successfully with S.,aureus. This CZE-UV technique can be applied to rapid diagnosis of enteritis caused by S.,aureus or other bacterial control-related fields needing rapid identification of target pathogens from microbial mixtures. In theory, this method is suitable for the detection of any bacterium as long as corresponding bacterium-specific antibody-coated latex is available. [source] The Composition of Jerusalem Artichoke (Helianthus tuberosus L.) Spirits Obtained from Fermentation with Bacteria and YeastsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 1 2005K. Szambelan Abstract The composition of spirits distilled from fermentation of Jerusalem artichoke (Helianthus tuberosus L.) tubers was compared by means of gas chromatography. The microorganisms used in the fermentation processes were the bacterium Zymomonas mobilis, strains,3881 and 3883, the distillery yeast Saccharomyces cerevisiae, strains,Bc16a and D2 and the Kluyveromyces fragilis yeast with an active inulinase. The fermentation of mashed tubers was conducted using a single culture of the distillery yeast Saccharomyces cerevisiae and the bacterium Zymomonas mobilis (after acid or enzymatic hydrolysis) as well as Kluyveromyces fragilis (sterilized mashed tubers). The tubers were simultaneously fermented by mixed cultures of the bacterium or the distillery yeast with K.,fragilis. The highest ethanol yield was achieved when Z.,mobilis,3881 with a yeast demonstrating inulinase activity was applied. The yield reached 94,% of the theoretical value. It was found that the distillates resulting from the fermentation of mixed cultures were characterized by a relatively lower amount of by-products compared to the distillates resulting from the single species process. Ester production of 0.30,2.93,g/L, responsible for the aromatic quality of the spirits, was noticed when K.,fragilis was applied for ethanol fermentation both in a single culture process and also in the mixed fermentation with the bacterium. Yeast applied in this study caused the formation of higher alcohols to concentrations of 7.04,g/L much greater than those obtained with the bacterium. The concentrations of compounds other than ethanol obtained from Jerusalem artichoke mashed tubers, which were fermented by Z.,mobilis, were lower than those achieved for yeasts. [source] Regulatory impact on insect biotechnology and pest managementENTOMOLOGICAL RESEARCH, Issue 4 2007Chris A. WOZNIAK Abstract The application of insect biotechnology is promising for the development of environmentally compatible pest management solutions. As we have refined and enhanced genetic engineering techniques in several insect species that cause significant economic loss and public health injury, it has become clear that insect biotechnology will move forward as one of the key tools of pest management in agriculture and in the human environment. Well characterized genetic elements can be manipulated toward specific aims and maintain a viable insect, albeit one with diminished capacity to exchange genetic material, vector a virus or bacterium, or complete its life cycle. Despite this degree of knowledge and precision, there remain unanswered questions regarding environmental fate, release and public acceptance of this technology. The uncertainty surrounding any novel technology inevitably increases the level of regulatory scrutiny associated with its use. Although the term "insect biotechnology" has many connotations, it certainly includes the genetic modification of symbiotic or commensally associated microbes as a means of delivering a trait (e.g. a toxin) to manage plant and human diseases and insect pests. The distinction between this paratransgenic approach and direct genetic modification of insect pests is an important one biologically as well as from a regulatory standpoint. The regulatory framework for microbial applications to agriculture is in many instances in place; however, we must strive to forge the development of guidelines and regulations that will foster deployment of insect biotechnologies. [source] Hydrogen peroxide-induced oxidative stress responses in Desulfovibrio vulgaris HildenboroughENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Aifen Zhou Summary To understand how sulphate-reducing bacteria respond to oxidative stresses, the responses of Desulfovibrio vulgaris Hildenborough to H2O2 -induced stresses were investigated with transcriptomic, proteomic and genetic approaches. H2O2 and induced chemical species (e.g. polysulfide, ROS) and redox potential shift increased the expressions of the genes involved in detoxification, thioredoxin-dependent reduction system, protein and DNA repair, and decreased those involved in sulfate reduction, lactate oxidation and protein synthesis. A gene coexpression network analysis revealed complicated network interactions among differentially expressed genes, and suggested possible importance of several hypothetical genes in H2O2 stress. Also, most of the genes in PerR and Fur regulons were highly induced, and the abundance of a Fur regulon protein increased. Mutant analysis suggested that PerR and Fur are functionally overlapped in response to stresses induced by H2O2 and reaction products, and the upregulation of thioredoxin-dependent reduction genes was independent of PerR or Fur. It appears that induction of those stress response genes could contribute to the increased resistance of deletion mutants to H2O2 -induced stresses. In addition, a conceptual cellular model of D. vulgaris responses to H2O2 stress was constructed to illustrate that this bacterium may employ a complicated molecular mechanism to defend against the H2O2 -induced stresses. [source] Cold adaptation in the marine bacterium, Sphingopyxis alaskensis, assessed using quantitative proteomicsENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Lily Ting Summary The cold marine environment constitutes a large proportion of the Earth's biosphere. Sphingopyxis alaskensis was isolated as a numerically abundant bacterium from several cold marine locations, and has been extensively studied as a model marine bacterium. Recently, a metabolic labelling platform was developed to comprehensively identify and quantify proteins from S. alaskensis. The approach incorporated data normalization and statistical validation for the purpose of generating highly confident quantitative proteomics data. Using this approach, we determined quantitative differences between cells grown at 10°C (low temperature) and 30°C (high temperature). Cold adaptation was linked to specific aspects of gene expression: a dedicated protein-folding system using GroESL, DnaK, DnaJ, GrpE, SecB, ClpB and PPIase; polyhydroxyalkanoate-associated storage materials; a link between enzymes in fatty acid metabolism and energy generation; de novo synthesis of polyunsaturated fatty acids in the membrane and cell wall; inorganic phosphate ion transport by a phosphate import PstB homologue; TonB-dependent receptor and bacterioferritin in iron homeostasis; histidine, tryptophan and proline amino acid metabolism; and a large number of proteins without annotated functions. This study provides a new level of understanding on how important marine bacteria can adapt to compete effectively in cold marine environments. This study is also a benchmark for comparative proteomic analyses with other important marine bacteria and other cold-adapted organisms. [source] Novel natural parabens produced by a Microbulbifer bacterium in its calcareous sponge host Leuconia niveaENVIRONMENTAL MICROBIOLOGY, Issue 6 2009Elodie Quévrain Summary A broad variety of natural parabens, including four novel structures and known ethyl and butyl parabens, were obtained from culture of a Microbulbifer sp. bacterial strain isolated from the temperate calcareous marine sponge Leuconia nivea (Grant 1826). Their structures were elucidated from spectral analysis, including mass spectrometry and 1D and 2D nuclear magnetic resonance. Their antimicrobial activity evaluated against Staphylococcus aureus was characterized by much higher in vitro activity of these natural paraben compounds 3,9 than commercial synthetic methyl and propyl parabens, usually used as antimicrobial preservatives. Compounds 4 and 9 revealed a bacteriostatic effect and compounds 6 and 7 appeared as bactericidal compounds. Major paraben compound 6 was also active against Gram positive Bacillus sp. and Planococcus sp. sponge isolates and was detected in whole sponge extracts during all seasons, showing its persistent in situ production within the sponge. Moreover, Microbulbifer sp. bacteria were visualized in the sponge body wall using fluorescence in situ hybridization with a probe specific to L4-n2 phylotypes. Co-detection in the sponge host of both paraben metabolites and Microbulbifer sp. L4-n2 indicates, for the first time, production of natural parabens in a sponge host, which may have an ecological role as chemical mediators. [source] Widespread occurrence of an intranuclear bacterial parasite in vent and seep bathymodiolin musselsENVIRONMENTAL MICROBIOLOGY, Issue 5 2009Frank U. Zielinski Summary Many parasitic bacteria live in the cytoplasm of multicellular animals, but only a few are known to regularly invade their nuclei. In this study, we describe the novel bacterial parasite "Candidatus Endonucleobacter bathymodioli" that invades the nuclei of deep-sea bathymodiolin mussels from hydrothermal vents and cold seeps. Bathymodiolin mussels are well known for their symbiotic associations with sulfur- and methane-oxidizing bacteria. In contrast, the parasitic bacteria of vent and seep animals have received little attention despite their potential importance for deep-sea ecosystems. We first discovered the intranuclear parasite "Ca. E. bathymodioli" in Bathymodiolus puteoserpentis from the Logatchev hydrothermal vent field on the Mid-Atlantic Ridge. Using primers and probes specific to "Ca. E. bathymodioli" we found this intranuclear parasite in at least six other bathymodiolin species from vents and seeps around the world. Fluorescence in situ hybridization and transmission electron microscopy analyses of the developmental cycle of "Ca. E. bathymodioli" showed that the infection of a nucleus begins with a single rod-shaped bacterium which grows to an unseptated filament of up to 20 ,m length and then divides repeatedly until the nucleus is filled with up to 80 000 bacteria. The greatly swollen nucleus destroys its host cell and the bacteria are released after the nuclear membrane bursts. Intriguingly, the only nuclei that were never infected by "Ca. E. bathymodioli" were those of the gill bacteriocytes. These cells contain the symbiotic sulfur- and methane-oxidizing bacteria, suggesting that the mussel symbionts can protect their host nuclei against the parasite. Phylogenetic analyses showed that the "Ca. E. bathymodioli" belongs to a monophyletic clade of Gammaproteobacteria associated with marine metazoans as diverse as sponges, corals, bivalves, gastropods, echinoderms, ascidians and fish. We hypothesize that many of the sequences from this clade originated from intranuclear bacteria, and that these are widespread in marine invertebrates. [source] A pyrene-degrading consortium from deep-sea sediment of the West Pacific and its key member Cycloclasticus sp.ENVIRONMENTAL MICROBIOLOGY, Issue 8 2008Summary A pyrene-degrading bacterial consortium was obtained from deep-sea sediments of the Pacific Ocean. The consortium degraded many kinds of polycyclic aromatic hydrocarbons (PAHs), including naphthalene, phenanthrene, pyrene, acenaphthene, fluorene, anthracene, fluoranthene, 2-methylnaphthalene and 2,6-dimethylnaphthalene, but it did not grow with chrysene and benzo[,]pyrene. With methods of plate cultivation and polymerase chain reaction,denaturing gradient gel electrophoresis (PCR-DGGE), 72 bacteria belonging to 22 genera were detected from this consortium. Among the detected bacteria, the following genera frequently occurred: Flavobacterium, Cycloclasticus, Novosphingobium, Halomonas, Achromobacter, Roseovarius and Alcanivorax. The first two genera showed the strongest bands in denaturing gradient gel electrophoresis (DGGE) profiles and appeared in all PAH treatments. By now, only one isolate designated P1 was confirmed to be a pyrene degrader. It was identified to be Cycloclasticus spirillensus (100%). Although P1 can degrade pyrene independently, other bacteria, such as Novosphingobium sp. (Band 14), Halomonas sp. (Band 16) and an unidentified bacterium (Band 35), were involved in pyrene degradation in some way; they persist in the consortium in the test of dilution to extinction if only the consortium was motivated with pyrene. However, the secondary most important member Flavobacterium sp. evaded from the community at high dilutions. As a key member of the consortium, P1 distinguished itself by both cell morphology and carbon source range among the isolates of this genus. Based on intermediate analyses of pyrene degradation, P1 was supposed to take an upper pathway different from that previously reported. Together with the results of obtained genes from P1 homology with those responsible for naphthalene degradation, its degradation to pyrene is supposed to adopt another set of genes unique to presently detected. Summarily, an efficient pyrene-degrading consortium was obtained from the Pacific Ocean sediment, in which Cycloclasticus bacterium played a key role. This is the first report to exploit the diversity of pyrene-degrading bacteria in oceanic environments. [source] Molecular link of different stages of the trematode host of Neorickettsia risticii to Acanthatrium oregonenseENVIRONMENTAL MICROBIOLOGY, Issue 8 2008Kathryn E. Gibson Summary Neorickettsia risticii, the obligatory intracellular bacterium that causes Potomac horse fever, has been detected in various developmental stages of digenetic trematodes in the environment. Neorickettsia risticii -infected gravid trematodes were identified as Acanthatrium oregonense, based on morphologic keys. However, whether immature trematodes harbouring N. risticii are also A. oregonense was unknown. The objective of this study was to infer the life cycle of N. risticii -positive trematode hosts and transstadial transmission of the bacterium by molecularly characterizing the relationship among adult and immature stages of trematodes confirmed infected with N. risticii. Sequences of 18S ribosomal RNA genes up to 1922 bp in size were obtained from infected adult gravid trematodes, sporocysts and cercariae, and metacercariae. The sequences from the different immature stages of trematode are closely related to those of adult trematodes, some with 100% sequence identity; thus, they likely are life stages of A. oregonense. Comparisons with known 18S ribosomal RNA gene sequences of other digenetic trematodes indicated that all tested stages of the N. risticii -positive trematodes belong to the family Lecithodendriidae, supporting the morphological identification. [source] Dominant sugar utilizers in sediment of Lake Constance depend on syntrophic cooperation with methanogenic partner organismsENVIRONMENTAL MICROBIOLOGY, Issue 6 2008Nicolai Müller Summary Six strains of novel bacteria were isolated from profundal sediment of Lake Constance, a deep freshwater lake in Germany, by direct dilution of the sediment in mineral agar medium containing a background lawn of the hydrogen-scavenging Methanospirillum hungatei as a syntrophic partner. The numbers of colony-forming units obtained after incubation for more than 2 months were in the same range as those of total bacterial counts determined by DAPI staining (up to 108 cells per millilitre) suggesting that these organisms were dominant members of the community. Identical dilution series in the absence of methanogenic partners yielded numbers that were lower by two to three orders of magnitude. The dominant bacteria were isolated in defined co-culture with M. hungatei, and were further characterized. Growth was slow, with doubling times of 22,28 h at 28°C. Cells were small, 0.5 × 5 ,m in size, Gram-positive, and formed terminal oval spores. At 20°C, glucose was fermented by the co-culture strain BoGlc83 nearly stoichiometrically to 2 mol of acetate and 1 mol of methane plus CO2. At higher temperatures, also lactate and traces of succinate were formed. Anaerobic growth depended strictly on the presence of a hydrogen-scavenging partner organism and was inhibited by bromoethane sulfonate, which together indicate the need for a syntrophic partnership for this process. Strain BoGlc83 grew also aerobically in the absence of a partner organism. All enzymes involved in ATP formation via glycolysis and acetyl CoA were found, most of them at activities equivalent to the physiological substrate turnover rate. This new type of sugar-fermenting bacterium appears be the predominant sugar utilizer in this environment. The results show that syntrophic relationships can play an important role also for the utilization of substrates which otherwise can be degraded in pure culture. [source] Life in Darwin's dust: intercontinental transport and survival of microbes in the nineteenth centuryENVIRONMENTAL MICROBIOLOGY, Issue 12 2007Anna A. Gorbushina Summary Charles Darwin, like others before him, collected aeolian dust over the Atlantic Ocean and sent it to Christian Gottfried Ehrenberg in Berlin. Ehrenberg's collection is now housed in the Museum of Natural History and contains specimens that were gathered at the onset of the Industrial Revolution. Geochemical analyses of this resource indicated that dust collected over the Atlantic in 1838 originated from the Western Sahara, while molecular-microbiological methods demonstrated the presence of many viable microbes. Older samples sent to Ehrenberg from Barbados almost two centuries ago also contained numbers of cultivable bacteria and fungi. Many diverse ascomycetes, and eubacteria were found. Scanning electron microscopy and cultivation suggested that Bacillus megaterium, a common soil bacterium, was attached to historic sand grains, and it was inoculated onto dry sand along with a non-spore-forming control, the Gram-negative soil bacterium Rhizobium sp. NGR234. On sand B. megaterium quickly developed spores, which survived for extended periods and even though the numbers of NGR234 steadily declined, they were still considerable after months of incubation. Thus, microbes that adhere to Saharan dust can live for centuries and easily survive transport across the Atlantic. [source] The obligate aerobic actinomycete Streptomyces coelicolor A3(2) survives extended periods of anaerobic stressENVIRONMENTAL MICROBIOLOGY, Issue 12 2007Geertje Van Keulen Summary The actinomycete Streptomyces coelicolor is an obligate aerobe that is found in soil and aqueous habitats. The levels of oxygen in these environments can vary considerably, which raises the question of how these bacteria survive during periods of anaerobiosis. Although S. coelicolor cannot grow in the complete absence of oxygen, we demonstrate here that it is capable of microaerobic growth and maintaining viability through several weeks of strict anaerobiosis. Both resting and germinated spores are able to survive abrupt exposure to anaerobiosis, which contrasts the situation with Mycobacterium species where gradual oxygen depletion is required to establish a latent state in which the bacterium is able to survive extended periods of anaerobiosis. Growth of S. coelicolor resumes immediately upon re-introduction of oxygen. Taken together these findings indicate that survival is not restricted to spores and suggest that the bacterium has evolved a mechanism to maintain viability and a membrane potential in the hyphal state. Furthermore, although we demonstrate that several members of the genus also survive long periods of anaerobic stress, one species, Streptomyces avermitilis, does not have this capacity and might represent a naturally occurring variant that is unable to adopt this survival strategy. [source] Heterotrophic symbionts of phototrophic consortia: members of a novel diverse cluster of Betaproteobacteria characterized by a tandem rrn operon structureENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Kristina R. Pfannes Summary Phototrophic consortia represent the most highly developed type of interspecific association of bacteria and consist of green sulfur bacterial epibionts attached around a central colourless rod-shaped bacterium. Based on 16S rRNA gene sequencing, the central bacterium of the consortium ,Chlorochromatium aggregatum' was recently shown to represent a novel and phylogenetically isolated lineage of the Comamonadaceae within the ,-subgroup of the Proteobacteria. To date, 19 types of phototrophic consortia are distinguished based on the different 16S rRNA gene sequences of their epibionts, but the diversity and phylogenetic relationships of the heterotrophic partner bacteria are still unknown. We developed an approach based on the specific rrn (ribosomal RNA) operon structure of the central bacterium of ,C. aggregatum' to recover 16S rRNA gene sequences of other central bacteria and their close relatives from natural consortia populations. Genomic DNA of the central bacterium of ,C. aggregatum' was first enriched several hundred-fold by employing a selective method for growth of consortia in a monolayer biofilm followed by a purification of the genome of the central bacterium by cesium chloride-bisbenzimidazole equilibrium density gradient centrifugation. A combination of inverse PCR, cloning and sequencing revealed that two rrn operons of the central bacterium are arranged in a tandem fashion and are separated by an unusually short intergenic region of 195 base pairs. This rare gene order was exploited to screen various natural microbial communities by PCR. We discovered a diverse and previously unknown subgroup of Betaproteobacteria in the chemoclines of freshwater lakes. This group was absent in other freshwater and soil samples. All the 16S rRNA gene sequences recovered are related to that of the central bacterium of ,C. aggregatum'. Fluorescence in situ hybridization indicated that two of these sequences originated from central bacteria of different phototrophic consortia, which, however, were only distantly related to the central bacterium of ,C. aggregatum'. Based on a detailed phylogenetic analysis, these central bacterial symbionts of phototrophic consortia have a polyphyletic origin. [source] Identification of genes involved in the biosynthesis of the cytotoxic compound glidobactin from a soil bacteriumENVIRONMENTAL MICROBIOLOGY, Issue 7 2007Barbara Schellenberg Summary Glidobactins (syn. cepafungins) are a family of structurally related cytotoxic compounds that were isolated from the soil bacterial strain K481-B101 (ATCC 53080; DSM 7029) originally assigned to Polyangium brachysporum and, independently, from an undefined species related to Burkholderia cepacia. Glidobactins are acylated tripeptide derivatives that contain a 12-membered ring structure consisting of the two unique non-proteinogenic amino acids erythro -4-hydroxy- l -lysine and 4(S)-amino-2(E)-pentenoic acid. Here we report the cloning and functional analysis of a gene cluster (glbA,glbH) involved in glidobactin synthesis from K481-B101, which according to its 16S rRNA sequence belongs to the Burkholderiales. The putative encoded proteins include a mixed non-ribosomal peptide/polyketide synthetase whose structure and architecture allowed to build a biosynthetic pathway model explaining the biosynthesis of the unique peptide part of glidobactins. Intriguingly, among the more than 600 bacterial strains whose genome sequence is currently available, homologous gene clusters were found in Burkholderia pseudomallei, the causing agent of melioidosis, and in the insect pathogen Photorhabdus luminescens, strongly suggesting that these organisms are capable to synthesize compounds similar to glidobactins. In addition, a glb gene cluster that was inactivated by transposon-mediated rearrangements was also present in Burkholderia mallei, a very close relative of B. pseudomallei and the causing agent of glanders in horse-like animals. [source] The ttgGHI solvent efflux pump operon of Pseudomonas putida DOT-T1E is located on a large self-transmissible plasmidENVIRONMENTAL MICROBIOLOGY, Issue 6 2007José J. Rodríguez-Herva Summary Pseudomonas putida DOT-T1E is a solvent-tolerant strain able to grow in the presence of > 1% (v/v) toluene in the culture medium. A set of multidrug efflux pumps have been found to play a major role in the tolerance of this bacterium to organic solvents (Rojas et al., J Bacteriol 183: 3967,3973). In the course of studies of the mechanisms underlying solvent tolerance in DOT-T1E, we isolated a spontaneous solvent-sensitive mutant derivative which had lost the genes encoding the TtgGHI efflux pump, the most important extrusion element in quantitative terms. Genomic comparisons between the mutant and its parental strain by microarray analysis revealed that in addition to the ttgVW-ttgGHI gene cluster, another group of genes, highly similar to those found in the Tn4653A and ISPpu12 transposable elements of the TOL plasmid pWW0 from P. putida mt-2, were also absent from this strain. Further analysis demonstrated that strain DOT-T1E harboured a large plasmid (named pGRT1) that was lost from the solvent-sensitive mutant. Mapping analysis revealed that the ttgVW-ttgGHI genes and the Tn4653A -like transposon are borne by the pGRT1 plasmid. Plasmid pGRT1 is highly stable and its frequency of loss is below 10,8 per cell per generation under a variety of growth conditions, including nutritional and physical stresses. The pGRT1 plasmid is self-transmissible, and its acquisition by the toluene-sensitive P. putida KT2440 and Pseudomonas aeruginosa PAO1 increased the recipient's tolerance to toluene up to levels similar to those exhibited by P. putida DOT-T1E. We discuss the importance and potential benefits of this plasmid for the development of bacteria with enhanced solvent tolerance, and its potential impact for bioremediation and whole-cell biotransformations. [source] Microbial community structure of ethanol type fermentation in bio-hydrogen productionENVIRONMENTAL MICROBIOLOGY, Issue 5 2007Nanqi Ren Summary Three continuous stirred-tank reactors (CSTRs) were used for H2 production from molasses wastewater at influent pH of 6.0,6.5 (reactor A), 5.5,6.0 (reactor B), or 4.0,4.5 (reactor C). After operation for 28 days, the microbial community formed ethanol type (C), propionate type (A) and ethanol-butyrate-mixed type (B) fermentation. The H2 production rate was the highest for ethanol type fermentation, 0.40 l (g VSS),1 day,1 or 0.45 l H2 (g COD removed),1. Microbial community dynamics and diversity were analysed using double-gradient denaturing gradient gel electrophoresis (DG-DGGE). Denaturing gradient gel electrophoresis profiles indicated that the community structures changed quickly in the first 14 days. Phylogenetic analysis indicated that the dominant bacterial groups were low G+C Gram-positive bacteria, Bacteroides, ,-Proteobacteria and Actinobacteria; ,-Proteobacteria, ,-Proteobacteria, ,-Proteobacteria and Spirochaetes were also presented as minor groups in the three reactors. H2 -producing bacteria were affiliated with Ethanoligenens, Acetanaerobacterium, Clostridium, Megasphaera, Citrobacter and Bacteroides. An ethanol-based H2 -producing bacterium, Ethanoligenens harbinense CGMCC1152, was isolated from reactor C and visualized using fluorescence in situ hybridization (FISH) to be 19% of the eubacteria in reactor C. In addition, isoenzyme activity staining for alcohol dehydrogenase (ADH) supported that the majority of ethanol-producing bacteria were affiliated with Ethanoligenens in the microbial community. [source] Microbial communities in a porphyry copper tailings impoundment and their impact on the geochemical dynamics of the mine wasteENVIRONMENTAL MICROBIOLOGY, Issue 2 2007Nouhou Diaby Summary The distribution and diversity of acidophilic bacteria of a tailings impoundment at the La Andina copper mine, Chile, was examined. The tailings have low sulfide (1.7% pyrite equivalent) and carbonate (1.4% calcite equivalent) contents and are stratified into three distinct zones: a surface (0-70-80 cm) ,oxidation zone' characterized by low-pH (2.5,4), a ,neutralization zone' (70,80 to 300,400 cm) and an unaltered ,primary zone' below 400 cm. A combined cultivation-dependent and biomolecular approach (terminal restriction enzyme fragment length polymorphism and 16S rRNA clone library analysis) was used to characterize the indigenous prokaryotic communities in the mine tailings. Total cell counts showed that the microbial biomass was greatest in the top 125 cm of the tailings. The largest numbers of bacteria (109 g,1 dry weight of tailings) were found at the oxidation front (the junction between the oxidation and neutralization zones), where sulfide minerals and oxygen were both present. The dominant iron-/sulfur-oxidizing bacteria identified at the oxidation front included bacteria of the genus Leptospirillum (detected by molecular methods), and Gram-positive iron-oxidizing acidophiles related to Sulfobacillus (identified both by molecular and cultivation methods). Acidithiobacillus ferrooxidans was also detected, albeit in relatively small numbers. Heterotrophic acidophiles related to Acidobacterium capsulatum were found by molecular methods, while another Acidobacterium -like bacterium and an Acidiphilium sp. were isolated from oxidation zone samples. A conceptual model was developed, based on microbiological and geochemical data derived from the tailings, to account for the biogeochemical evolution of the Piuquenes tailings impoundment. [source] The nodPQ genes in Azospirillum brasilense Sp7 are involved in sulfation of lipopolysaccharidesENVIRONMENTAL MICROBIOLOGY, Issue 11 2005Els Vanbleu Summary Here we report on the presence of sulfated lipopolysaccharide molecules in Azospirillum brasilense, a plant growth-promoting rhizosphere bacterium. Chemical analysis provided structural data on the O-antigen composition and demonstrated the possible involvement of the nodPQ genes in O-antigen sulfation. [source] Effect of thorium on the growth and capsule morphology of BradyrhizobiumENVIRONMENTAL MICROBIOLOGY, Issue 10 2003Mónica Santamaría Summary The thorium effect on Bradyrhizobium growth was assayed in liquid media. Th4+ inhibited the growth of Bradyrhizobium (Chamaecytisus) BGA-1, but this effect decreased in the presence of suspensions of live or dead bacterial cells. Th4+ induced the formation of a gel-like precipitate when added to a dense suspension of B. (Chamaecytisus) BGA-1 cells. Viable Bradyrhizobium cells remained in suspension after precipitate formation. Thorium was recovered in the precipitate, in which polysaccharide, lipopolysaccharide and proteins were also found. After Th4+ addition, the morphology of B. (Chamaecytisus) BGA-1 or Bradyrhizobium japonicum USDA 110 sedimented cells studied by scanning electron microscopy changed from an entangled network of capsulated bacteria to uncapsulated individual cells and an amorphous precipitate. Energy-dispersive X-ray spectroscopy showed that thorium was mainly in the amorphous fraction. Precipitate was also formed between B. (Chamaecytisus) BGA-1 and Al3+, which was also toxic to this bacterium. Precipitate induced by Th4+ or Al3+ was found in all Bradyrhizobium and Sinorhizobium strains tested, but not in Rhizobium, Salmonella typhimurium, Aerobacter aerogenes or Escherichia coli. These results suggest a specific defence mechanism based on metal precipitation by extracellular polymers. [source] A strain isolated from gas oil-contaminated soil displays chemotaxis towards gas oil and hexadecaneENVIRONMENTAL MICROBIOLOGY, Issue 10 2003Mariana P. Lanfranconi Summary In this report we describe the isolation of a strain from soil contaminated with gas oil by taking bacteria from a chemotactic ring on gas oil-containing soft agar plates. Partial 16 S rDNA sequencing of the isolated strain showed 99.1% identity with Flavimonas oryzihabitans. It was not only able to degrade different aliphatic hydrocarbons but it was also chemotactic towards gas oil and hexadecane, as demonstrated by the use of three different chemotaxis methods, such as agarose plug and capillary assays and swarm plate analysis. In addition, the strain was chemotactic to a variety of carbon sources that serve as growth substrates, including glucose, arabinose, mannitol, glycerol, gluconate, acetate, succinate, citrate, malate, lactate and casaminoacids. This is the first report on chemotaxis of a hydrocarbon-degrading bacterium towards a pure alkane, such as hexadecane. The fact that environmental isolates show chemotaxis towards contaminant/s present in the site of isolation suggests that chemotaxis might enhance biodegradation by favouring contact between the degrading microorganism and its substrate. [source] Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacteriumENVIRONMENTAL MICROBIOLOGY, Issue 10 2002Husen Zhang Summary Water treatment technologies are needed that can remove perchlorate from drinking water without introducing organic chemicals that stimulate bacterial growth in water distribution systems. Hydrogen is an ideal energy source for bacterial degradation of perchlorate as it leaves no organic residue and is sparingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium (Dechloromonas sp. strain HZ) that grows with carbon dioxide as sole carbon source. Strain HZ is a Gram-negative, rod-shaped facultative anaerobe that was isolated from a gas-phase anaerobic packed-bed biofilm reactor treating perchlorate-contaminated groundwater. The ability of strain HZ to grow autotrophically with carbon dioxide as the sole carbon source was confirmed by demonstrating that biomass carbon (100.9%) was derived from CO2. Chemolithotrophic growth with hydrogen was coupled with complete reduction of perchlorate (10 mM) to chloride with a maximum doubling time of 8.9 h. Strain HZ also grew using acetate as the electron donor and chlorate, nitrate, or oxygen (but not sulphate) as an electron acceptor. Phylogenetic analysis of the 16S rRNA sequence placed strain HZ in the genus Dechloromonas within the , subgroup of the Proteobacteria. The study of this and other novel perchlorate-reducing bacteria may lead to new, safe technologies for removing perchlorate and other chemical pollutants from drinking water. [source] Stable augmentation of activated sludge with foreign catabolic genes harboured by an indigenous dominant bacteriumENVIRONMENTAL MICROBIOLOGY, Issue 10 2002Kazuya Watanabe Summary Comamonas sp. rN7 is a phenol-degrading bacterium that represents the dominant catabolic population in activated sludge. The present study examined the utility of this bacterium for establishing foreign catabolic genes in phenol-digesting activated sludge. The phc genes coding for phenol hydroxylase and its transcriptional regulators of C. testosteroni R5 were integrated into the chromosome of strain rN7. The specific phenol-oxygenating activity of a resultant transformant designated rN7(R503) was three times higher than the activity of strain rN7, and the phc genes were stably inherited by rN7(R503) grown in a non-selective laboratory medium. Inoculation of phenol-acclimatized activated sludge with rN7(R503) resulted in a high phenol-oxygenating activity and improved resistance to phenol-shock loading compared to sludge inoculated with either no cells, rN7 or R5. Quantitative competitive polymerase chain reaction (PCR) showed that the phc genes were retained in the rN7(R503)-inoculated sludge at a density of more than 108 copies per ml of mixed liquor for more than 35 days, whereas those in the R5-inoculated sludge disappeared rapidly. No transfer of the phc genes to other indigenous populations was apparent in the rN7(R503)-harbouring sludge. From these results, we concluded that the phenol treatment of the activated sludge was enhanced by the phc genes harboured by the rN7(R503) population. This study suggests a possible bioaugmentation strategy for stably utilizing foreign catabolic genes in natural ecosystems. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||