Degradation, microbial

Fries MR, LJ Forney, JM Tiedje (1998b) Phenol- and toluene-degrading microbial populations from an aquifer in which successful trichloroethene cometabolism occurred. Appl Environ Microbiol 63 1523-1530. 

Table 3 Techniques used to study degrading microbial community structures in various wastewater treatment systems... 

Keywoids Chiral synthon. Chiral building blocks. Stereospecific synthesis. Stereoselective degradation. Microbial transformation. 

Apajalahti,J. H. Salkinoja-Salonen, M. S. (1984). Absorption of pentachlorophenol (PCP) by bark chips and its role in microbial PCP degradation. Microbial Ecology, 10,359-67. 

Cell walls are biochemically rather inert with reduced digestibility to many organisms because of their complex cellulose, pectin, and lignin molecules. Callose and lignin are often accumulated at the site of infection or wounding (6,7) and form a penetration barrier. Synthesis of inhibitory proteins (e.g., lectins, protease inhibitors) or enzymes (e.g., chitinase, lysozyme, hydrolases, nucleases) that could degrade microbial cell walls or other microbial constituents would be protective, as well as synthesis of peroxidase and phe-nolase, which could help inactivate phytotoxins produced by many bacteria and fungi. These proteins are either stored in the vacuole... 

Soil temperature influences chemical degradation, microbial decomposition, and volatilization. For example, no aldrin or heptachlor was lost from frozen soils, but at 6°C, 16-27% of the dose applied to soil was lost in 56 days at 26°C, 51-55% disappeared and at 46°C, 86-98% was lost. Diazinon was also degraded faster at higher temperatures than at low ones (Edwards, 1973b). Temperature also influences the adsorption of pesticide in soils because adsorption is a exothermic process, so that increased temperatures decrease adsorption and release pesticides. 

In general, both P2HAs and P3HAs, are subjected to acid-based catalyst hydrolytic decomposition in a low-temperature range, and only biotechnologically produced PHAs are subjected in addition to enzymatic decomposition due to extracellular enzymes. Some microorganisms excrete extracellular depolymerases to degrade microbial PHAs and to utilize the decomposed compounds as nutrients. 

An important issue emerged from the results of experiments with 14C-labeled pyrene added to a pristine forest soil (Guthrie and Pfaender 1998) (1) extensive mineralization took place only in samples amended with a pyrene-degrading microbial community, (2) there was a substantially greater nonextractable fraction of label in soils containing either the natural or introduced microflora compared with an azide-treated control, (3) metabolites that could be released by acid and base extraction remained in the soil after 270 days of incubation. 

Pesticide-Degrading Microbial Populations. Innovative microbiological investigations have paved the way for increased understanding of the mechanisms of enhanced degradation. One of the... 

Biological Degradation. Microbial (enzymatic) attack can occur on silk, but it is the water-soluble sericin, that is the more readily depolymerised. 

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