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.

Genetics of bacteriocins produced by lactic acid bacteria

Abstract: Lactic acid bacteria produce a variety of bacteriocins that have recently come under detailed investigation. The biochemical and genetic characteristics of these antimicrobial proteins are reviewed and common elements are discussed between the different classes of bacteriocins produced by these Gram-positive bacteria.

Protein content and protein synthesis rates of planktonic marine bacteria

Abstract: Bacterial carbon production is an important parameter in understanding the flows of carbon and energy in aquatic ecosystems, but has been difficult to measure. Present methods are based on measuring the rate of cell production, and thus require a knowledge of cellular carbon content of the growing bacteria to convert cell production into carbon production. We have examined the possibility that protein synthesis rate of pelagic bacteria might serve as the basis for directly estimating bacterial carbon production. We measured bacterial protein content and protein production of pelagic bacteria. Bacterial protein content was measured as amino acids by high performance liquid chromatography of cell hydrolysates of bacterial assemblages of mean diameters from 0.026 to 0.4 km. Cellular protein:volume (w/v) in the largest bacteria was 15.2 '10 (similar to cultured Escherichia coli] but increased with decreasing cell size to 46.5 % in 0.026 pm bacteria. Protein per bacterium was correlated with cell volume by the power function y = 8 8 . ~ 2 ~ ' (r2 = 0.67; p C 0.01; n = 25) . An inventory of major bacterial macromolecular pools revealed that cell protein:dry weight and cell protein:carbon were essentially constant (63 % and 54 %. respectively) for the entire cell size range although cell protein:volume increased with decreasing cell size. Thus, the smaller cells in the size range were rich in carbon and dry weight and poor in water compared with larger cells. We established the experimental conditions for estimating protein synthesis on the basis of 3H leucine incorporation by bacteria, and determined the necessary parameters (including the intracellular isotope dilution by HPLC) for converting 3~ leucine incorporation into protein synthesis rate. In samples from Scripps Institution of Oceanography pier the intracellular isotope dilution was only 2-fold. In a field study in Southern California Bight bacterial protein production and %I-thymidine incorporation methods yielded comparable rates of bacterial production. Bacterial protein production method was an order of magnitude more sensitive and yielded bacterial carbon production directly without the need to know the cell size of the part of the assemblage in growth state.

The taxonomic significance of fermentative versus oxidative metabolism of carbohydrates by various gram negative bacteria

Abstract: For many years bacteriologists have observed that some bacteria produce acid from carbohydrates only under aerobic conditions while others produce acid both under aerobic and anaerobic conditions. The significance of these observations does not seem to have been appreciated generally by taxonomists. Studies of bacterial physiology have made it increasingly evident that the bacterial metabolism of carbohydrates may be accomplished by two apparently fundamentally different mechanisms (see for example Porter, 1946; Werkman and Wilson, 1951). By one mechanism, appropriately called fermentation, the glucose molecule first is phosphorylated and then split into two triose molecules which undergo further changes. This process is independent of oxygen. By the other mechanism, which we shall call oxidation, the glucose molecule is not split into two triose molecules, but the aldehyde group is oxidized to a carboxyl group forming gluconic acid. Further oxidation may take place to form various products such as 2-ketogluconic acid. Several studies of this mechanism, summarized by Sebek and Randles (1952), have failed to detect phosphorylation of the glucose molecule preliminary to oxidation. In the absence of compounds such as nitrates, the oxidation of carbohydrates is a strictly aerobic process, whereas fermentation is an anaerobic process.