Amino acids bacteria

Peptidoglycan D-amino acids Bacteria, mainly gram-positive strains... 

More than 700 amino acids have been discovered in Nature and most of them are a-amino acids. Bacteria, fungi and algae and other plants provide nearly all these, which exist either in the free form or bound up into larger molecules (as constituents of peptides and proteins and other types of amide, and of alkylated and ester-ified structures). 

Enzymes that possess the same catalytic activity but are evolutionarily unrelated and play very diverse biological functions can be found, for example, in a group of PLP-dependent enzymes with desulfhydrase activity, that is, enzymes that release H2S from thiol amino acids. Bacteria employ desulfhydrases not only in the metabolism of sulfurated amino acids and in the adaptation to new nutrient sources, but also, sometimes, as virulence factors. An E. coli enzyme with desulfhydrase activity is even known to act as a modulator of gene expression, although this function seems to be unrelated to catalysis. Sulfide production by PLP-dependent enzymes is also important in vertebrates, where H2S has been shown to act as a neuromodulator. " ... 

M.p. 140°C. An amino-acid occasionally formed in the hydrolysis products of proteins and occurring in the urine of some birds as dibenzoylornithine. Ornithine is a precursor of arginine in plants, animals and bacteria. 

The product quaUty considerations for nonphotosynthetic microorganisms are similar to those for algae. Tables 6 and 7 present composition and amino acid analyses, respectively, for selected bacteria, yeasts, molds, and higher fungi produced on a large pilot-plant or commercial scale. Table 8 summarizes results of proteia quaUty and digestibiUty studies. 

Most of the bacteria, yeasts, molds, and higher fungi of interest for SCP production are deficient in methionine and must be supplemented with this amino acid to be suitable for animal feeding or human food appHcations. Also, lysine—arginine ratios should be adjusted in poultry rations in which yeast SCP is used (62). Human feeding studies have shown that only limited quantities of yeast such as Candida utilis can be added to food products without adverse effects on flavor (63). 

The nutrient sparing effect of antibiotics may result from reduction or elimination of bacteria competing for consumed and available nutrients. It is also recognized that certain bacteria synthesize vitamins (qv), amino acids (qv), or proteins that may be utilized by the host animal. Support of this mode of action is found in the observed nutritional interactions with subtherapeutic use of antibiotics in animal feeds. Protein concentration and digestibiHty, and amino acid composition of consumed proteins may all influence the magnitude of response to feeding antibiotics. Positive effects appear to be largest... 

After World War II, analytical methods for amino acids were improved and new methods were iatroduced. The first was microbial assay usiag lactic acid bacteria which require all of the regular amino acids for growth. Manometric determiaation (by use of a Warburg manometer) of CO2 Hberated by the... 

In the 1950s, a group of coryneform bacteria which accumulate a large amount of L-glutamic acid in the culture medium were isolated (21). The use of mutant derivatives of these bacteria offered a new fermentation process for the production of many other kinds of amino acids (22). The amino acids which are produced by this method are mostiy of the T.-form, and the desired amino acid is singly accumulated. Therefore, it is very easy to isolate it from the culture broth. Rapid development of fermentative production and en2ymatic production have contributed to the lower costs of many protein amino acids and to their availabiUty in many fields as economical raw materials. 

Microbiological procedures which exploit the ability of bacteria and photosynthetic algae to incorporate exogenous labeled precursors such as 14CO2, SO%, and 32pQ3- [ can be used to label complex molecules in cells such as proteins (qv) and nucleic acids (qv), which are then processed to give labeled constituents such as uniformly labeled C-amino acids, C-nucleotides, C-fipids, LS-amino acids, etc (8). 

Physiological Role of Citric Acid. Citric acid occurs ia the terminal oxidative metabolic system of virtually all organisms. This oxidative metabohc system (Fig. 2), variously called the Krebs cycle (for its discoverer, H. A. Krebs), the tricarboxyUc acid cycle, or the citric acid cycle, is a metaboHc cycle involving the conversion of carbohydrates, fats, or proteins to carbon dioxide and water. This cycle releases energy necessary for an organism s growth, movement, luminescence, chemosynthesis, and reproduction. The cycle also provides the carbon-containing materials from which cells synthesize amino acids and fats. Many yeasts, molds, and bacteria conduct the citric acid cycle, and can be selected for thek abiUty to maximize citric acid production in the process. This is the basis for the efficient commercial fermentation processes used today to produce citric acid. 

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