Bacterial degradation mechanisms

Haggblom M (1990) Mechanisms of bacterial degradation and transformation of chlorinated monoaromatic compounds. J Basic Microbiol 30 115-141. 

Extracellular breakdown mechanism used by white-rot fungus allows it to treat a wider range of contaminants than bacterial degraders. 

The approach of Casiot et al. [21] was soon accepted and followed in the held of Se speciation. Wrobel et al. [91] applied a bacterium (Arthrobacter luteus) derived lysing enzyme mixture added with PMSF to study the intermediary molecules of Se metabolism of Se-enriched yeast without proteolysis. In order to tailor the cell wall degrading mechanism to the samples under test, Michalke et al. [77] used bacterial lisozyme and pronase E, either alone or in combination, for the Se speciation of Se-enriched lactic acid bacteria. Independent and simultaneous experiments were carried out with the two enzymes, thus achieving outstanding total Se-extraction efficiency (85-105 percent) with the sole application of pronase E and relatively low chromatographic recovery (8-12 percent) (still... 

Intrinsic resistance to biocides as a consequence of bacterial degradative activities is thus not a major mechanism of insusceptibility. There are, of course, examples of plasmid-mediated enzymes that confer resistance to inorganic (and sometimes organic) mercurials and these will be discussed later... 

The chemical reactivity of simple heterocyclic aromatic compounds varies widely in electrophilic substitution reactions, thiophene is similar to benzene and pyridine is less reactive than benzene, while furan and pyrrole are susceptible to polymerization reactions conversely, pyridine is more readily susceptible than benzene to attack by nucleophilic reagents. These differences are to a considerable extent reflected in the susceptibility of these compounds and their benzo analogues to microbial degradation. In contrast to the almost universal dioxygenation reaction used for the bacterial degradation of aromatic hydrocarbons, two broad mechanisms operate for heterocyclic aromatic compounds ... 

Selective Biotransformation Potential. A number of factors might limit the possible extrapolation of results to the in vivo situation. Firstly, compounds may be degraded by different cells or mechanisms, e.g. due to acid conditions in the stomach, or by bacterial degradation in the lower parts of the G.I.-tract. Also, other organs may be involved in the biotransformation of a compound, possibly resulting in very specific metabolites. On the other hand, the isolation of hepatocytes results both in the disruption of the typical liver structure, and a selection of cell-types. This may be an important advantage of liver slices, especially now that their preparation has become much easier, faster and more reproducible (20, 21, 22, 23, 24). Last but not least, monolayer... 

Increased serum digoxin following erythromycin in selected patients (only 10% of population appears to be at risk) mechanism appears to be erythromycin-induced reduction in the bacterial degradation of digoxin in the intestine. 

Information on the hydrolytic activity in marine sediments has been obtained from the use of model substrates labeled with fluorescent dyes such as methylumbelliferone (MUF) or fluorescein. These substrates may be small dimeric molecules, the hydrolytic cleavage of which releases the fluorescence signal, which is then indicative of the activity of specific enzymes such as glucosidase, chitobiase, lipase, ami-nopeptidase or esterase (Chrost 1991). Also large fluorescently labeled polymers such as the polysaccharides laminarin or pullulan have been used in experiments to demonstrate the mechanism and kinetics of bacterial degradation (Amosti 1996). 

Fortunately, bed rest, rehydration, parenteral nutrition, and therapy directed at decreasing the production of toxins that result from bacterial degradation of nitrogenous substrates in the gut lumen (e.g., administration of lactulose, which reduces gut ammonia levels by a variety of mechanisms, the use of enemas and antibiotics to decrease the intestinal flora, a low-protein diet) prevented Percy Veere from progressing to the later stages of hepatic encephalopathy. As with most patients who survive an episode of fulminant hepatic failure, recovery to his previous state of health occurred over the next 3 months. Percy s liver function studies returned to normal, and a follow-up liver biopsy showed no histologic abnormalities. 

Seubert, W. and E. Pass, 1964a. Studies on the bacterial degradation of isoprenoids. V. The mechanism of... 

---