Bacteria

About: Bacteria is a research topic. Over the lifetime, 23676 publications have been published within this topic receiving 715990 citations. The topic is also known as: eubacteria.

Growth of desulfovibrio in lactate or ethanol media low in sulfate in association with H2-utilizing methanogenic bacteria.

Abstract: In the analysis of an ethanol-CO2 enrichment of bacteria from an anaerobic sewage digestor, a strain tentatively identified as Desulfovibrio vulgaris and an H2-utilizing methanogen resembling Methanobacterium formicicum were isolated, and they were shown to represent a synergistic association of two bacterial species similar to that previously found between S organism and Methanobacterium strain MOH isolated from Methanobacillus omelianskii. In lowsulfate media, the desulfovibrio produced acetate and H2 from ethanol and acetate, H2, and, presumably, CO2 from lactate; but growth was slight and little of the energy source was catabolized unless the organism was combined with an H2-utilizing methanogenic bacterium. The type strains of D. vulgaris and Desulfovibrio desulfuricans carried out the same type of synergistic growth with methanogens. In mixtures of desulfovibrio and strain MOH growing on ethanol, lactate, or pyruvate, diminution of methane produced was stoichiometric with the moles of sulfate added, and the desulfovibrios grew better with sulfate addition. The energetics of the synergistic associations and of the competition between the methanogenic system and sulfate-reducing system as sinks for electrons generated in the oxidation of organic materials such as ethanol, lactate, and acetate are discussed. It is suggested that lack of availability of H2 for growth of methanogens is a major factor in suppression of methanogenesis by sulfate in natural ecosystems. The results with these known mixtures of bacteria suggest that hydrogenase-forming, sulfate-reducing bacteria could be active in some methanogenic ecosystems that are low in sulfate.

Molecular and microscopic identification of sulfate-reducing bacteria in multispecies biofilms.

Abstract: The population architecture of sulfidogenic biofilms established in anaerobic fixed-bed bioreactors was characterized by selective polymerase chain reaction amplification and fluorescence microscopy. A region of the 16S rRNA common to resident sulfate-reducing bacteria was selectively amplified by the polymerase chain reaction. Sequences of amplification products, with reference to a collection of 16S rRNA sequences representing most characterized sulfate-reducing bacteria, were used to design both general and specific hybridization probes. Fluorescent versions of these probes were used in combination with fluorescence microscopy to visualize specific sulfate-reducing bacterial populations within developing and established biofilms.

The formation of hydrogen sulfide and methyl mercaptan by oral bacteria.

Abstract: The capacity to form volatile sulfur compounds was tested in bacteria isolated from subgingival microbiotas and in a representative number of reference strains. A majority of the 75 tested oral bacterial species and 7 unnamed bacterial taxa formed significant amounts of hydrogen sulfide from L-cysteine. The most active bacteria were found in the genera Peptostreptococcus, Eubacterium, Selenomonas, Centipeda, Bacteroides and Fusobacterium. Methyl mercaptan from L-methionine was formed by some members of the genera Fusobacterium, Bacteroides, Porphyromonas and Eubacterium. When incubated in serum for 7 d, the most potent producers of hydrogen sulfide were Treponema denticola and the black-pigmented species, Bacteroides intermedius, Bacteroides loescheii, Porphyromonas endodontalis and Porphyromonas gingivalis. P. endodontalis and P. gingivalis also produced significant amounts of methyl mercaptan in serum. No other volatile sulfur compound was detected in serum or in the presence of L-cysteine and L-methionine. These findings significantly increase the list of oral bacteria known to produce volatile sulfur compounds.

Diversity in Chemotaxis Mechanisms among the Bacteria and Archaea

Abstract: The study of chemotaxis describes the cellular processes that control the movement of organisms toward favorable environments. In bacteria and archaea, motility is controlled by a two-component system involving a histidine kinase that senses the environment and a response regulator, a very common type of signal transduction in prokaryotes. Most insights into the processes involved have come from studies of Escherichia coli over the last three decades. However, in the last 10 years, with the sequencing of many prokaryotic genomes, it has become clear that E. coli represents a streamlined example of bacterial chemotaxis. While general features of excitation remain conserved among bacteria and archaea, specific features, such as adaptational processes and hydrolysis of the intracellular signal CheY-P, are quite diverse. The Bacillus subtilis chemotaxis system is considerably more complex and appears to be similar to the one that existed when the bacteria and archaea separated during evolution, so that understanding this mechanism should provide insight into the variety of mechanisms used today by the broad sweep of chemotactic bacteria and archaea. However, processes even beyond those used in E. coli and B. subtilis have been discovered in other organisms. This review emphasizes those used by B. subtilis and these other organisms but also gives an account of the mechanism in E. coli.

Life after log.

Abstract: A remarkable feature of bacterial species is their capacity for rapid growth when nutrients are available and conditions are appropriate for growth. Perhaps even more remarkable is their ability to remain viable under conditions not propitious for growth. Many bacteria have evolved highly sophisticated mechanisms that allow them to maintain cell viability during starvation and resume growth rapidly when nutrients again become available. Some species form dormant spores, while others form multicellular aggregates and fruiting bodies in response to starvation conditions (26, 34). But even without the formation of such elaborately differentiated cells, many bacteria, among them Escherichia, Salmonella, and Vibrio spp., enter a starvation-induced program that results in a metabolically less active and more resistant state. Examination of starved cells using light microscopy reveals changes in cell morphology. Escherichia coli cells become much smaller and almost spherical when they enter stationary phase (22, 31). This phenomenon is even more striking for a number of marine bacteria which greatly decrease in size during starvation and form ultramicrocells, as small as 0.03 ,um3 (28). Ultramicrocells result from cells that undergo several cell divisions without an increase in biomass and then a further decrease in their size as a result of endogenous metabolism. One possible selective advantage of the reductive divisions seen in marine bacteria is to improve the survival of the clonal population by increasing the probability that some cells will encounter nutrients (38). In E. coli, these changes in cell size and shape are accompanied by changes in the subcellular compartments; the cytoplasm is condensed and the volume of the periplasm increases (48). The surface properties of starved cells are also different from those of growing cells. The surface of many marine bacteria becomes increasingly hydrophobic and the cells become more adhesive during starvation (28). Changes in the fatty acid composition of the cell membranes have been seen during starvation of several species (28). For example, in E. coli there is a conversion of all unsaturated membrane fatty acids to the cyclopropyl derivatives as cells enter stationary phase (14). Vibrio sp. strain S14 acquires new fimbraelike structures and forms cellular aggregates or clumps after prolonged starvation (1). In E. coli, such starvation-induced aggregates appear to form as the result of a self-generated and secreted attractant that is sensed by the chemotaxis machinery (7). The cell wall synthesized during amino acid starvation has