Bacteria metabolizing

HUR H G, LAY J o Jr, BEGER R D, FREEMAN J p and RAFii F (2000) Isolation of human intestinal bacteria metabolizing the natural isoflavone glycosides daidzin and genistin. Arch Microbiol. 174 (6) 422-8. 

Jones, K.L., Kim, S.-W. and Keasbng, J.D. (2000) Low-copy plasmids can perform as well as or better than high-copy plasmids for metabolic engineering of bacteria. Metabolic Engineering, 2, 328-338. 

Clayton RK, Sistrom WR (1978) In Merrick JM (ed) The photosynthetic bacteria metabolism of reserve materials. Plenum Press, New York... 

Fumaric Aero Inhibition. Another means of preventing malo-lactic fermentation is to add fumaric acid after alcoholic fermentation is complete (45, 46, 47,48). The inhibition is relative and its extent is dependent on the amount added. The susceptibility to fumaric acid is also dependent on the strain of malo-lactic bacteria tested (49). However, we know of no case where fumaric acid addition at the levels suggested by Cofran and Meyer (45) (about 0.05%) did not delay malo-lactic fermentation under normal winemaking conditions. This includes several experiments from our pilot winery (50). Nevertheless, we have not been hasty to recommend the use of fumaric acid as an inhibitor because 1) of the difficulty in solubilizing the acid in wine 2) we do not know the mechanism of action of its inhibition [Pilone (47, 48) has shown that the bacteria metabolize low levels of fumaric acid to lactic acid but, at inhibitory levels at wine pH, the acid is bactericidal] and 3) of the desirability of minimizing the use of chemical additives. 

Biofilms enhance bacteria-DOM interactions by several means. Their spatial and chemical heterogeneity provides additional sorption sites for DOM compared with clean surfaces. Their loose architecture with interstitial voids and channels increases diffusivity and to some extent allows convective flow within biofilm structures. Because bacteria metabolize organic matter sorbed to the biofilm, a diffusion flux from the free water to the biofilm is maintained. Large proportions of organic matter sorbed to the biofilm are not instantly turned over but remain in the biofilm as a reservoir, which buffers direct effects of DOM depletion in the water column. 

Subsequent yeast and lactic bacteria metabolism in the press-run juice occurs in a medium rich in sugars and with a high potential for microbial growth (Barre, 1969). This helps explain the speed of the second fermentation phase, the early "biologic stability" of the wines, and the possible yeast and bacterial competition. 

Fungi and bacteria metabolize a wide variety of PAHs (Cerniglia, 1993 Sutherland et al., 1995 Juhasz Naidu, 2000), although the principal pathways used by these groups are different. Some PAH bioactivation pathways found in mammals are also observed in microorganisms (Cerniglia Gibson, 1980). 

Relevant Aspects of Lactic Acid Bacteria Metabolisms... 

Ben-Bassat A., Lamed R., and Zeikus J. G. (1981) Ethanol production by thermophilic bacteria metabolic control of end product formation in Thermoanaerobium brockii. J. Bacteriol. 146, pp. 192-199. 

The oxidation of organic matter in anaerobic sediments can utilize a number of species as oxidants, of which sulfate is the most important. In seawater at pH values close to 8, sulfate-reducing bacteria metabolize organic matter according to the following simplified equation ... 

There are four major bile acids (see Figures 47-5 to 47-7). Cholic acid and chenodeoxycholic acid, the primary bile acids, are synthesized in the liver. Bacteria metabolize these primary bile acids to the secondary bile acids—deoxy-cholic acid and lithocholic acid, respectively. Bile acids are conjugated in the liver with the amino acids glycine or taurine. This decreases passive absorption in the biliary tree and proximal small intestine, but permits conservation through active transport in the terminal ileum. This combi-... 

With few exceptions, enzymatic processes in carbohydrates cause degradation. Enzymes are used in the form of pure or semipure preparations or together with their producers, i.e., microorganisms. Currently, semisynthetic enzymes are also in use. Alcoholic fermentation is the most common method of utilization of monosaccharides, sucrose, and some polysaccharides, e.g., starch. Lactic acid fermentation is another important enzymatic process. Lactic acid bacteria metabolize mono- and disaccharides into lactic acid. This acid has a chiral center thus either D(-), L(+), or racemic products can be formed. In the human organism, only the L(+) enantiomer is metabolized, whereas the D(-) enantiomer is concentrated in blood and excreted with urine. Among lactic acid bacteria, only Streptococcus shows specificity in the formation of particular enantiomers, and only the L(+) enantiomer is produced. 

Sulfate reduction. All plants, animals, and bacteria metabolize sulfur in order to synthesize amino acids such as cysteine and methionine. The sulfur may be assimilated as sulfate or as organic molecules containing sulfate. The reduction of sulfate in biosynthesis is termed assimilatory sulfate reduction and can take place in aerobic or anaerobic environments (cf. Goldhaber and Kaplan 1974 Rheinheimer 1981 Cullimore 1991). 

Yeasts and bacteria metabolize xylose by following sHghtly different pathways as showing in Fig. 1. Yeasts rely on xylose reductase and xyHtol dehydrogenase, but bacteria rely on xylose isomerase, to convert xylose to xylulose [2, 3]. Although the Saccharomyces yeasts as well as other fermentative yeasts are not able to ferment xylose, Saccharomyces yeasts are able to ferment xylulose to ethanol [4]. Furthermore, they are also able to ferment xylose when a bacterial xylose isomerase is present in the medium [5]. This indicates that Saccharomyces yeasts lack only the enzymes for the conversion of xylose to xylulose. 

The large intestine extends from the ileocecal valve to the anus. It is wider than the small intestine except for the descending colon, which when empty may have the same diameter as the small intestine. Major functions of the colon are absorption of water, Na+, and other electrolytes, as well as temporary storage of excreta followed by their elimination. The colon harbors large numbers of mostly anaerobic bacteria that can cause disease if they invade tissues. These bacteria metabolize carbohydrates to lactate, short-chain fatty acids (acetate, propionate, and butyrate), and gases (CO2, CH4, and H2). Ammonia, a toxic waste product, is produced from urea and other nitrogenous compounds. Other toxic substances are also produced in the colon. Ammonia and amines (aromatic or aliphatic) are absorbed and transported to the liver via the portal blood, where the former is converted to urea (Chapter 17) and the latter is detoxified. The liver thus protects the rest of the body from toxic substances produced in the colon. Colonic bacteria can also be a source of certain vitamins (e.g., vitamin K, Chapter 36). 

Anthraquinone derivatives include cascara sagrada, sennosides, and casanthrol. Gut bacteria metabolizes these agents to their active compounds, but the exact mechanisms of action are not understood. Effects are limited to the colon, and stimulation of Auerbach s plexus may be involved. Recommendations for the use of these agents are similar to those for the diphenyhnethane derivatives. In most cases, intermittent use is acceptable daily use should be strongly discouraged. 

Aeetie acid is produced photoehemieally mainly from reactions of the peroxy acetyl radical (CH3CO3) wifli oflier peroxy radieals. For example, the reaction of CH3CO3 with HO2 is known to lead to about 20% CH3C(0)OH (Tyndall et al, 2001). Aeetie acid in the gas phase is also produced by reaction of ozone with various olefins like propene, butene or pentene (Atkinson and Arey, 2003). A total photochemical source strength of 120 Tg/year has been reported (Baboukas et al, 2000). The contribution of direct emissions from anthropogenie (biomass eombustion, motor exhaust) and biogenie (bacteria metabolisms, emission from soil and vegetation) sourees is estimated at 48 Tg/year (Chebbi and Carlier, 1996). 

In another example, biodegradation of azetidine ring structures was investigated using the toxic, plant, natural product L-azetidine-2-carboxylic acid (ACA). ACA is made in large quantities by certain plants, such as Lily of the Valley, to ward off pathogens [26]. Despite this, some bacteria metabolize ACA productively (Fig. 3). Pseudomonas strain A2C was isolated from soil beneath Lily of the Valley plants and was able to grow on L-azetidine-... 

Various cell culture lines and ruminal bacteria metabolize T-2 toxin by deacylation of specific... 

The ring forming assay on semisolid agar—a technique that was introduced by J. Adler in the nineteen sixties [4]— is perhaps the most commonly used technique even today. In this assay, bacteria are put at a certain spot in a plate containing semisolid agar and a homogeneous, low concentration of a metabolizable chemoattractant. The bacteria metabolize the chemoattractant and thereby produce a chemoattractant... 

Various enteric bacteria metabolized DMNA through denitrosation, by which dimethylamine and nitrite were formed, and dimethylamine was not further metabolized [75]. 

Table 13.1 Lactic acid bacteria metabolic groups and tbeir characteristics (Hammes Vogel, 1995)...

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