Bacteria synthesizing

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... 

Vitamin Bjg is not synthesized by animals or by plants. Only a few species of bacteria synthesize this complex substance. Carnivorous animals easily acquire sufficient amounts of Bjg from meat in their diet, but herbivorous creatures typically depend on intestinal bacteria to synthesize Bjg for them. This is sometimes not sufficient, and certain animals, including rabbits, occasionally eat their feces in order to accumulate the necessary quantities of Big. 

An intriguing question which is, of course, as yet impossible to answer, is why the bacteria synthesize so many and so diverse polysaccharide components. A common speculation is that this gives them an advantage in their protection against the bacteriophages. The latter have to develop specific... 

The importance of bacteria in mediating Mn(II) oxidation in certain environments is evident. But, the mechanisms whereby bacteria oxidize Mn(II) are poorly understood. Some bacteria synthesize proteins or other materials that enhance the rate of Mn(II) oxidation (.52). Other strains of bacteria require oxidized manganese to oxidize Mn(II) (53), suggesting that they may catalyse the oxidation of Mn(II) on the manganese oxide surface. Other bacteria may catalyse the oxidation of Mn(II) on iron oxide surfaces, as iron is associated with manganese deposits on bacteria collected in the eastern subtropical North Pacific (54). 

Natural pesticides show promise for alleviating the pollution problem. Plants make some of these pesticides for their own protection, and bacteria synthesize others for purposes that are poorly understood. In spite of their promise, however, products based on natural pesticides have been on the market for years without much success, their major drawbacks being high cost and a reputation for unreliability. The present hope is that continuing research can... 

Folic acid is vital for both humans and bacteria. Bacteria synthesize this compound, but humans are unable to synthesize it and, consequently, obtain the necessary amounts from the diet, principally from green vegetables and yeast. This allows selectivity of action. Therefore, sulfa drugs are toxic to bacteria because folic acid biosynthesis is inhibited, whereas they produce little or no ill effects in humans. The structural relationships between carboxylic acids and sulfonic acids that we have observed in rationalizing chemical reactivity are now seen to extend to some biological properties. 

Cells regulate their lipid composition to achieve a constant membrane fluidity under various growth conditions. For example, bacteria synthesize more unsaturated fatty acids and fewer saturated ones when cultured at low temperatures than when cultured at higher temperatures (Table 11-2). As a result of this adjustment in lipid composition, membranes of bacteria cultured at high or low temperatures have about the same degree of fluidity. 

Plants and bacteria synthesize all 20 common amino acids. Mammals can synthesize about half the others are required in the diet (essential amino acids). 

Bacteria synthesize D-amino acids from L-amino acids in racemization reactions requiring pyridoxal phosphate. 

The synthesis of some enzymes is referred to as constitutive, implying that the enzyme is formed no matter what the environmental conditions of the cell. For example, many bacteria synthesize the enzymes required to catabolize glucose under all conditions of growth. Other enzymes, known as inducible, are often produced only in small amounts. However, if... 

Some bacteria synthesize C50 carotenoids such as decaprenoxanthin (Fig. 22-5), the extra carbon atoms at each end being donated from additional prenyl groups, apparently at the stage of cyclization of lycopene.134 Thus, a carbocation derived by elimination of pyrophosphate from dimethylallyl-PP could replace the H+ shown in the first step of Eq. 22-11. The foregoing descriptions deal with only a few of the many known structural modifications of carotenoids.2 135 136... 

Biotin required for growth and normal function by animals, yeast, and many bacteria is seldom found in deficiency in humans because the intestinal bacteria synthesize it in sufficient quantity to meet requirements. Biotin deficiency does occur, however, 111 animals fed raw whiles of eggs. The egg white contains a protein, avidin, which combines with biotin, and tins complex is not broken down by enzymes of the gastrointestinal tract. Hence, a deficiency develops. 

A wide range of compounds also inhibit a number of the enzyme systems that are involved in the biosynthesis of purines and pyrimidines in bacteria. For example, sulphonamide bacteriostatics inhibit dihydropteroate synthetase, which prevents the formation of folic acid in both humans and bacteria. However, although both mammals and bacteria synthesize their folic acid from PABA (Figure 7.12), mammals can also obtain it from their diet. In contrast, trimethoprim specifically inhibits bacterial DHF, which prevents the conversion... 

Cystic fibrosis patients are usually advised to take more than the recommended daily amounts of these vitamins in order to prevent deficiency. A common problem associated with poor absorption of fat-soluble vitamins is deficiency of vitamin K. Vitamin K is required by the liver to produce many blood coagulation factors. Part of the problem for cystic fibrosis patients is their chronic antibiotic therapy, which decreases the bacterial population of the colon colonic bacteria synthesize vitamin K. Vitamin K deficiency leads to prolonged blood-clotting time. Vitamin D deficiency could cause rickets in a child or osteomalacia in adults. Vitamin A deficiency leads to night blindness, skin and other ocular defects. 

Intestinal bacteria synthesize riboflavin, and fecal losses of the vitamin may be five- to six-fold higher than intake. It is possible that bacterial synthesis makes a significant contribution to riboflavin intake, because there is carrier-mediated uptake of riboflavin into colonocytes in culture. The activity of the carrier is increased in riboflavin deficiency and decreased when the cells are cultured in the presence of high concentrations of riboflavin. The same carrier mechanism seems to be involved in tissue uptake of riboflavin (Said et al., 2000). 

Because ROS attack is an important defense mechanism against infections in animals. Cars have functions in bacteria that protect them against the immune system. Many bacteria synthesize Cars for their protection, and many virulent forms of Cars are colored deeply by Cars. 

A closer look at these events reveals that bacteria synthesize folic acid using several enzymes, including one called dihydropteroate synthetase, which catalyzes the attachment of p-aminobenzoic acid to a pteridine ring system. When sulfanilamide is present it competes with the p-amino-benzoic acid (note the structural similarity) for the active site on the enzyme. This activity makes it a competitive inhibitor. Once this site is occupied on the enzyme, folic acid synthesis stops and bacterial growth stops. Folic acid can also be synthesized in the laboratory. ... 

Plants and some bacteria synthesize all 20 amino acids (see also Chapter 2). Humans (and other animals) can synthesize about half of them (the nonessential amino acids) but require the other half to be supplied by the diet (the essential amino acids). Diet must also provide a digestible source of nitrogen for synthesis of the nonessential amino acids. The eight essential amino acids are isoleucine, leucine lysine, methionine, phenylalanine, threonine, tryptophan, and valine. In infants, histidine (and possibly arginine) is required for optimal development and growth and is thus essential. In adults, histidine is nonessential, except in uremia. Under certain conditions. 

Other antibiotics may not be quite as selective and may react with both human and bacterial enzymes, thereby making them somewhat toxic. An example of the latter is chloramphenicol, an antibiotic that targets the protein synthesis apparatus. Since both humans and bacteria synthesize proteins, the potential for some crossreactivity is obvious. This antibiotic can have some deleterious side effects in humans. The level of the deleterious effect is a matter of debate and it is a duty of governmental regulatory agencies to monitor these properties. 

Minor monosaccharides released upon hydrolysis of sediments can also provide source indications. For example, the methoxy (i.e. O-methyl) monosaccharides 3-O-methylxylose and 6-O-methylmannose are abundant in the coccolithophore species Emiliania huxleyi. Bacteria synthesize a wider range of these components together with deoxy monosaccharides (Klok et al. 1984a). 

There are two major mechanisms by which bacteria synthesize UFAs mostly of them, including Escherichia coli, synthesize UFAs anaerobically (Mansilla et al., 2004) whereas some prokaryotes such as cyanobacteria, bacilli, mycobacteria and pseudomonads use an oxygen-dependent fatty acid desaturation pathway (Mansilla and de Mendoza, 2005 Phetsuksiri et al., 2003 Zhu et al., 2006). 

E. coli and other Gram-negative bacteria synthesize the IPP and dimethylallyl diphosphate (DMAPP) by the mevalonate-independent pathway, also known as the nonmevalonate pathway (other names are deoxyxylulose phosphate or methylerythritol phosphate pathway). In contrast. Gram-positive bacteria and eukaryotes, including yeast, synthesize the side chain precursors by the mevalonate pathway. Interestingly, Streptomycetes possess both the mevalonate and nonmevalonate pathways. These pathways are the subject of Chapters 1.12, 1.13, 1.14, 1.22. 

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