Topic
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.
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TL;DR: The unicellular soil-freshwater alga Chlamydomonas reinhardtii was found to secrete substances that mimic the activity of the N-acyl-l-homoserine lactone signal molecules used by many bacteria for quorum sensing regulation of gene expression, providing evidence that the secretion of AHL mimics by the alga could be effective in disruption of quorumensing in naturally encountered bacteria.
Abstract: The unicellular soil-freshwater alga Chlamydomonas reinhardtii was found to secrete substances that mimic the activity of the N-acyl-L-homoserine lactone (AHL) signal molecules used by many bacteria for quorum sensing regulation of gene expression. More than a dozen chemically separable but unidentified substances capable of specifically stimulating the LasR or CepR but not the LuxR, AhyR, or CviR AHL bacterial quorum sensing reporter strains were detected in ethyl acetate extracts of C. reinhardtii culture filtrates. Colonies of C. reinhardtii and Chlorella spp. stimulated quorum sensing-dependent luminescence in Vibrio harveyi, indicating that these algae may produce compounds that affect the AI-2 furanosyl borate diester-mediated quorum sensing system of Vibrio spp. Treatment of the soil bacterium Sinorhizobium meliloti with a partially purified LasR mimic from C. reinhardtii affected the accumulation of 16 of the 25 proteins that were altered in response to the bacterium's own AHL signals, providing evidence that the algal mimic affected quorum sensing-regulated functions in this wild-type bacterium. Peptide mass fingerprinting identified 32 proteins affected by the bacterium's AHLs or the purified algal mimic, including GroEL chaperonins, the nitrogen regulatory protein PII, and a GTP-binding protein. The algal mimic was able to cancel the stimulatory effects of bacterial AHLs on the accumulation of seven of these proteins, providing evidence that the secretion of AHL mimics by the alga could be effective in disruption of quorum sensing in naturally encountered bacteria.
236 citations
TL;DR: The results suggest that the real-time PCR assay developed in this study is useful and reliable for quantifying the populations of ANAMMOX bacteria in environmental and engineering samples.
236 citations
01 Jan 1982
TL;DR: The most resistant microorganisms were able to survive 2min exposure to 10mgoffree chlorine perliter as discussed by the authors, and the most sensitive bacteria were killed bychlorine concentrations of 1.0mgliter-' orless, and included most gram-positive micrococci, CorynebacteriumlArthrobacter, Klebsiella, PseudomonaslAlcaligenes, FlavobacteriumIMoraxella, andAcinetobacter.
Abstract: microorganisms inchlorinated waters. Bacteriaretained onthesurfaces of2.0-p.m Nuclepore membranefilters weresignificantly moreresistant tofree chlorine compared tothetotal microbial population recovered on0.2-p.m membrane filters, presumably because aggregated cells or bacteria attached tosuspended particulate matterexhibit moreresistance than unassociated microorganisms. Inaccordance withthishypothesis, scanning electron microscopy ofsuspended particulate matterfromthewatersamples revealed thepresence ofattached bacteria. Themostresistant microorganisms wereabletosurvive a2-min exposure to10mgoffree chlorine perliter. These included gram-positive spore-forming bacilli, actinomycetes, andsomemicrococci.Themostsensitive bacteria werereadily killed bychlorine concentrations of 1.0mgliter-' orless, andincluded mostgram-positive micrococci, CorynebacteriumlArthrobacter, Klebsiella, PseudomonaslAlcaligenes, FlavobacteriumIMoraxella, andAcinetobacter.
236 citations
TL;DR: Emerging evidence suggests that the metabolism of bacteria grown in vivo differs profoundly from their metabolism in axenic cultures.
Abstract: Bacterial metabolism has been studied intensively since the first observations of these 'animalcules' by Leeuwenhoek and their isolation in pure cultures by Pasteur. Metabolic studies have traditionally focused on a small number of model organisms, primarily the Gram negative bacillus Escherichia coli, adapted to artificial culture conditions in the laboratory. Comparatively little is known about the physiology and metabolism of wild microorganisms living in their natural habitats. For approximately 500-1000 species of commensals and symbionts, and a smaller number of pathogenic bacteria, that habitat is the human body. Emerging evidence suggests that the metabolism of bacteria grown in vivo differs profoundly from their metabolism in axenic cultures.
235 citations
TL;DR: Cell death was not associated with a reduction in culture turbidity or a loss of membrane integrity since morphologically normal membranes were observed by electron microscopy and only a small proportion of the cytoplasmic enzyme beta-galactosidase leaked into the supernatant fluid of acid-treated E. coli K12 cultures.
Abstract: When strains of Escherichia coli K12 and Salmonella spp. were incubated with 0.5-0.7 mol/l formic or propionic acid at pH 5.0, propionic acid was more active than formic acid. It killed 90% of the cell population within 60 min compared with over 3 h for formic acid. Cell death was not associated with a reduction in culture turbidity or a loss of membrane integrity since morphologically normal membranes were observed by electron microscopy and only a small proportion of the cytoplasmic enzyme beta-galactosidase leaked into the supernatant fluid of acid-treated E. coli K12 cultures.
235 citations