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Multiple Homologues (multiple + homologue)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

The genome of Syntrophomonas wolfei: new insights into syntrophic metabolism and biohydrogen production

ENVIRONMENTAL MICROBIOLOGY, Issue 8 2010
Jessica R. Sieber
Summary Syntrophomonas wolfei is a specialist, evolutionarily adapted for syntrophic growth with methanogens and other hydrogen- and/or formate-using microorganisms. This slow-growing anaerobe has three putative ribosome RNA operons, each of which has 16S rRNA and 23S rRNA genes of different length and multiple 5S rRNA genes. The genome also contains 10 RNA-directed, DNA polymerase genes. Genomic analysis shows that S. wolfei relies solely on the reduction of protons, bicarbonate or unsaturated fatty acids to re-oxidize reduced cofactors. Syntrophomonas wolfei lacks the genes needed for aerobic or anaerobic respiration and has an exceptionally limited ability to create ion gradients. An ATP synthase and a pyrophosphatase were the only systems detected capable of creating an ion gradient. Multiple homologues for ,-oxidation genes were present even though S. wolfei uses a limited range of fatty acids from four to eight carbons in length.Syntrophomonas wolfei, other syntrophic metabolizers with completed genomic sequences, and thermophilic anaerobes known to produce high molar ratios of hydrogen from glucose have genes to produce H2 from NADH by an electron bifurcation mechanism. Comparative genomic analysis also suggests that formate production from NADH may involve electron bifurcation. A membrane-bound, iron,sulfur oxidoreductase found in S. wolfei and Syntrophus aciditrophicus may be uniquely involved in reverse electron transport during syntrophic fatty acid metabolism. The genome sequence of S. wolfei reveals several core reactions that may be characteristic of syntrophic fatty acid metabolism and illustrates how biological systems produce hydrogen from thermodynamically difficult reactions. [source]

Gene diversity of CYP153A and AlkB alkane hydroxylases in oil-degrading bacteria isolated from the Atlantic Ocean

ENVIRONMENTAL MICROBIOLOGY, Issue 5 2010
Liping Wang
Summary Alkane hydroxylases, including the integral-membrane non-haem iron monooxygenase (AlkB) and cytochrome P450 CYP153 family, are key enzymes in bacterial alkane oxidation. Although both genes have been detected in a number of bacteria and environments, knowledge about the diversity of these genes in marine alkane-degrading bacteria is still limited, especially in pelagic areas. In this report, 177 bacterial isolates, comprising 43 genera, were obtained from 18 oil-degrading consortia enriched from surface seawater samples collected from the Atlantic Ocean. Many isolates were confirmed to be the first oil-degraders in their affiliated genera including Brachybacterium, Idiomarina, Leifsonia, Martelella, Kordiimonas, Parvibaculum and Tistrella. Using degenerate PCR primers, alkB and CYP153A P450 genes were surveyed in these bacteria. In total, 82 P450 and 52 alkB gene fragments were obtained from 80 of the isolates. These isolates mainly belonged to Alcanivorax, Bacillus, Erythrobacter, Martelella, Parvibaculum and Salinisphaera, some of which were reported, for the first time, to encode alkane hydroxylases. Phylogenetic analysis showed that both genes were quite diverse and formed several clusters, most of which were generated from various Alcanivorax bacteria. Noticeably, some sequences, such as those from the Salinisphaera genus, were grouped into a distantly related novel cluster. Inspection of the linkage between gene and host revealed that alkB and P450 tend to coexist in Alcanivorax and Salinisphaera, while in all isolates of Parvibaculum, only P450 genes were found, but of multiple homologues. Multiple homologues of alkB mostly cooccurred in Alcanivorax isolates. Conversely, distantly related isolates contained similar or even identical sequences. In summary, various oil-degrading bacteria, which harboured diverse P450 and alkB genes, were found in the surface water of Atlantic Ocean. Our results help to show the diversity of P450 and alkB genes in prokaryotes, and to portray the geographic distribution of oil-degrading bacteria in marine environments. [source]

MicroReview: Envelope stress responses and Gram-negative bacterial pathogenesis

MOLECULAR MICROBIOLOGY, Issue 5 2005
Tracy L. Raivio
Summary The ,E, Cpx and Bae envelope stress responses of Escherichia coli are involved in the maintenance, adaptation and protection of the bacterial envelope in response to a variety of stressors. Recent studies indicate that the Cpx and ,E stress responses exist in many Gram-negative bacterial pathogens. The envelope is of particular importance to these organisms because most virulence determinants reside in, or must transit through, this cellular compartment. The Cpx system has been implicated in expression of pili, type IV secretion systems and key virulence regulators, while the ,E pathway has been shown to be critical for protection from oxidative stress and intracellular survival. Homologues of the ,E, and Cpx-regulated protease DegP are essential for full virulence in numerous pathogens, and, like ,E, DegP appears to confer resistance to oxidative stress and intracellular survival capacity. Some pathogens contain multiple homologues of the Cpx-regulated, disulphide bond catalyst DsbA protein, which has been demonstrated to play roles in the expression of secreted virulence determinants, type III secretion systems and pili. This review highlights recent studies that indicate roles for the ,E, Cpx and Bae envelope stress responses in Gram-negative bacterial pathogenesis. [source]