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.

The amino acid pool in escherichia coli

Abstract: Bacteria maintain internally synthesized small molecules at high internal concentrations and in addition have the capacity to concentrate many compounds from the environment. Since the majority of these compounds are intermediates in synthesis, they are collectively termed the pool of metabolic intermediates or, simply, the "pool." However, the state of organization and ultimate chemical fate of exogenous compounds concentrated by the cell may be different from those of identical compounds synthesized by the cell.

Human colonic microbiota: ecology, physiology and metabolic potential of intestinal bacteria.

Abstract: In both health and disease, the colonic microbiota plays an important role in several areas of human physiology. This complex assemblage of microorganisms endows great metabolic potential on the large intestine, primarily through its degradative abilities. Many hundreds of different types of bacteria, varying widely in physiology and biochemistry, exist in a multitude of different microhabitats in the lumen of the large gut, the mucin layer and on mucosal surfaces. Both microbiota and host obtain clear benefits from association. For example, growth substrates from diet and body tissues, together with a relatively stable environment for bacteria to proliferate are provided by the host, which in turn has evolved to use butyrate, a bacterial fermentation product, as its principal source of energy for epithelial cells in the distal bowel. The main sources of carbon and energy for intestinal bacteria are complex carbohydrates (starches, non-starch polysaccharides). Carbohydrate metabolism is of great importance in the large intestine, since generically, and in terms of absolute numbers, the vast majority of culturable microorganisms are saccharolytic. The amounts and types of fermentation products formed by colonic bacteria depend on the relative amounts of each substrate available, their chemical structures and compositions, as well as the fermentation strategies (biochemical characteristics and catabolite regulatory mechanisms) of bacteria participating in depolymerization and fermentation of the substrates. Protein breakdown and dissimilatory amino acid metabolism result in the formation of a number of putatively toxic metabolites, including phenols, indoles and amines. Production of these substances is inhibited or repressed in many intestinal microorganisms by a fermentable source of carbohydrate. Owing to the anatomy and physiology of the colon, putrefactive processes become quantitatively more important in the distal bowel, where carbohydrate is more limiting.

Quantification of ammonia-oxidizing bacteria in arable soil by real-time PCR.

Abstract: Real-time PCR was used to quantify populations of ammonia-oxidizing bacteria representing the β subdivision of the classProteobacteria in samples of arable soil, both nitrogen fertilized and unfertilized, from Mellby, Sweden. Primers and probes targeting a 16S ribosomal DNA region of the ammonia-oxidizing bacteria were designed and used. In the fertilized soil there were ∼6.2 × 107 ammonia-oxidizing bacteria per g of soil, three times more than the number of bacteria in the unfertilized soil. The lytic efficiency of bead beating in these soils was investigated by using populations of free or loosely attached bacteria, bacteria tightly bound to particles, and bacteria in nonfractionated samples. The shapes of the curves generated in these tests showed that the concentration of template DNA released at various times remained constant after 10 to 100 s of bead beating.

Respiratory chains and bioenergetics of acetic acid bacteria.

Abstract: Publisher Summary The chapter discusses the respiratory chains and bioenergetics of acetic acid bacteria. Acetic acid bacteria are obligate aerobes and well known as “vinegar producers.” They produce acetic acid from ethanol by two sequential catalytic reactions of membrane-bound alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Besides alcohols and aldehydes, acetic acid bacteria are able to oxidize various sugars and sugar alcohols such as D-glucose, glycerol, and D-sorbitol. Such oxidation reactions are called “oxidative fermentations”, because they involve incomplete oxidation of alcohols or sugars accompanied by accumulation of the corresponding oxidation products in huge amounts in the growth medium. Bacteria capable of effecting oxidative fermentations are called “oxidative bacteria,” of which the most prominent are acetic acid bacteria. Acetic acid bacteria are also important for the fermentation industries to produce biomaterials such as vinegar and L-sorbose. Acetic acid bacteria are classified into two genera, Gluconobacter and Acetobacter of the family Acetobacteraceae. Gluconobacter species catalyze highly active oxidation reactions on ethanol or D-glucose— including also oxidative reactions on sugars such as D-gluconic acid, D-sorbitol, and glycerol. By contrast, Acetobacter species have a highly active ethanoloxidizing system but not enzymes for sugar oxidation. The respiratory chain in Acetobacter spp. has ubiquinone, cytochrome b , cytochrome c , and a terminal ubiquinol oxidase, which is either cytochrome a 1 or cytochrome o .