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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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Journal ArticleDOI
TL;DR: The FISH technique in which slurry hybridization is used holds great promise for use with phylogenetic probes and for automatic counting of soil bacteria.
Abstract: A fluorescence in situ hybridization (FISH) technique based on binding of a rhodamine-labelled oligonucleotide probe to 16S rRNA was used to estimate the numbers of ribosome-rich bacteria in soil samples. Such bacteria, which have high cellular rRNA contents, were assumed to be active (and growing) in the soil. Hybridization to an rRNA probe, EUB338, for the domain Bacteria was performed with a soil slurry, and this was followed by collection of the bacteria by membrane filtration (pore size, 0.2 micrometer). A nonsense probe, NONEUB338 (which has a nucleotide sequence complementary to the nucleotide sequence of probe EUB338), was used as a control for nonspecific staining. Counting and size classification into groups of small, medium, and large bacteria were performed by fluorescence microscopy. To compensate for a difference in the relative staining intensities of the probes and for binding by the rhodamine part of the probe, control experiments in which excess unlabelled probe was added were performed. This resulted in lower counts with EUB338 but not with NONEUB338, indicating that nonspecific staining was due to binding of rhodamine to the bacteria. A value of 4.8 x 10(8) active bacteria per g of dry soil was obtained for bulk soil incubated for 2 days with 0.3% glucose. In comparison, a value of 3.8 x 10(8) active bacteria per g of dry soil was obtained for soil which had been air dried and subsequently rewetted. In both soils, the majority (68 to 77%) of actively growing bacteria were members of the smallest size class (cell width, 0.25 to 0.5 micrometer), but the active (and growing) bacteria still represented only approximately 5% of the total bacterial population determined by DAPI (4', 6-diamidino-2-phenylindole) staining. The FISH technique in which slurry hybridization is used holds great promise for use with phylogenetic probes and for automatic counting of soil bacteria.

168 citations

Journal ArticleDOI
TL;DR: Results indicate that a chlorine dose of 30 mg/L could achieve a 2.2-3.4 log bacteria reduction in lagoon samples, however, increasing the dose of chlorine did not significantly enhance the disinfection activity due to the presence of chlorine-resistant bacteria.

168 citations

Journal ArticleDOI
TL;DR: With the use of an in vitro model system of nongrowing bacteria, a select group of beta-lactam antibiotics has been found that demonstrates a striking and unusual ability to kill nongrows bacteria despite phenotypic tolerance to conventional beta- lactamiotics.
Abstract: beta-Lactam antibiotics rapidly kill bacteria during logarithmic growth but fail to kill nongrowing cells. This trait is the most universal example of phenotypic tolerance (the ability of bacteria to evade the bactericidal activity of antibiotics). Both nongrowing and slowly growing bacteria are found very frequently during infection in vivo, and phenotypic tolerance to the bactericidal activity of antibiotics as a consequence of reduced growth rate can be detected in vivo. With the use of an in vitro model system of nongrowing bacteria, a select group of beta-lactam antibiotics has been found that demonstrates a striking and unusual ability to kill nongrowing bacteria despite phenotypic tolerance to conventional beta-lactam antibiotics. These same compounds also effectively kill phenotypically tolerant cells in cerebrospinal fluid and serum. The extension of bactericidal activity to nongrowing and slowly growing bacteria may be a major advance in efforts to improve the chemotherapy for infectious diseases.

168 citations

Journal ArticleDOI
TL;DR: The data suggest that Met degradation in Cheddar cheese will depend on the organism used in production, the amount of enzyme released during aging, and the amounts of Met in the matrix.
Abstract: Methanethiol has been strongly associated with desirable Cheddar cheese flavor and can be formed from the degradation of methionine (Met) via a number of microbial enzymes. Methionine gamma-lyase is thought to play a major role in the catabolism of Met and generation of methanethiol in several species of bacteria. Other enzymes that have been reported to be capable of producing methanethiol from Met in lactic acid bacteria include cystathionine beta-lyase and cystathionine gamma-lyase. The objective of this study was to determine the production, stability, and activities of the enzymes involved in methanethiol generation in bacteria associated with cheese making. Lactococci and lactobacilli were observed to contain high levels of enzymes that acted primarily on cystathionine. Enzyme activity was dependent on the concentration of sulfur amino acids in the growth medium. Met aminotransferase activity was detected in all of the lactic acid bacteria tested and alpha-ketoglutarate was used as the amino group acceptor. In Lactococcus lactis subsp. cremoris S2, Met aminotransferase was repressed with increasing concentrations of Met in the growth medium. While no Met aminotransferase activity was detected in Brevibacterium linens BL2, it possessed high levels of L-methionine gamma-lyase that was induced by addition of Met to the growth medium. Met demethiolation activity at pH 5.2 with 4% NaCl was not detected in cell extracts but was detected in whole cells. These data suggest that Met degradation in Cheddar cheese will depend on the organism used in production, the amount of enzyme released during aging, and the amount of Met in the matrix.

167 citations

Journal ArticleDOI
TL;DR: High prevalence of phenotypic resistance for aminoglycoside was found in isolates from Europe, and the ability of Lb.

167 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20235,286
202210,729
20211,047
20201,096
20191,044