Toxicity microbial transformation

L. Y. Young and C. E. CemigUa, eds.. Microbial Transformation and Degradation of Toxic Organic Chemicals, WUey-Liss, New York, 1995. 

Findlay M, S Fogel, L Conway, A Taddeo (1995) Field treatment of coal tar-contaminated soil based on results of laboratory treatment studies. In Microbial transformation and degradation of toxic organic chemicals (Eds LY Young, CE Cerniglia), pp. 487-513. Wiley-Liss, New York. 

Sutherland JB, Rafii F, Khan AA et al (1995) Mechanisms of polycyclic aromatic hydrocarbon degradation. In Young LY, Cemiglia CE (eds) Microbial transformation and degradation of toxic organic chemicals. Wiley, New York... 

The higher content of DDT metabolites (DDE + DDD) compared with DDT itself (i.e., (DDE + DDD)/DDT > 1) in surface waters indicates a high degree of microbial transformation of the initial compound in the soil. The DDE and DDD are formed by DDT dehydrochlorination and dechlorination, respectively. On the whole it means that loss or leaching of toxic compounds take place from RPA formed some decades ago. 

Toxic Substances Control Act (TSCA) List, Grignard reagents listed on, 72 833—834t, 75 256, 259 Toxic substances, regulation of, 27 829 removal of, 74 423 in microbial transformations, 76 412 Toxic use reduction (TUR) regulations, 27 590... 

One of the most undesirable aspects of microbial transformations in nature is the formation of toxicants. A large number of organic compounds which are themselves innocuous can be, and often are, converted to products that may be harmful to humans, animals, plants, and microorganisms. By such means, the environment may create a pollutant where none was present before. The process of forming toxic products from innocuous precursors is known as activation [171-177]. 

Swoboda-Goldberg, N.G. Chemical contamination of the environment sources, types, and fate of synthetic organic chemicals. In Microbial Transformation and Degradation of Toxic Organic Chemicals Young, L.Y., Cemiglia, C., Eds. Wiley-Liss NY, 1995 27-74. 

Limonene (92) is the most widely distributed terpene in nature after a-pinene [68]. The (+)-isomer is present in Citrus peel oils at a concentration of over 90% a low concentration of the (-)-isomer is found in oils from the Mentha species and conifers [26]. The first data on the microbial transformation of limonene date back to the sixties. A soil Pseudomonad was isolated by enrichment culture technique on limonene as the sole source of carbon [69]. This Pseudomonad was also capable of growing on a-pinene, / -pinene, 1-p-menthene and p-cymene. The optimal level of limonene for growth was 0.3-0.6% (v/v) although no toxicity was observed at 2% levels. Fermentation of limonene by this bacterium in a mineral-salts medium resulted in the formation of a large number of neutral and acidic products. Dihydrocarvone, carvone, carveol, 8-p-menthene-1,2-cw-diol, 8-p-menthen-1 -ol-2-one, 8-p-menthene-1,2-trans-diol and 1 -p-menthene-6,9-diol were among the neutral products isolated and identified. The acidic compounds isolated and identified were perillic acid, /Msopropenyl pimelic acid, 2-hydroxy-8-p-menthen-7-oic acid and... 

Differences in rates of transformation and/or utilization between the two systems are possibly due to a) constant input vs. single input of p-coumaric acid and nutrient solution, b) aerobic (open system) vs. more anaerobic (closed system) conditions, c) little chance for accumulation of transformation products and/or toxic microbial byproducts (constant flushing of system) vs. potential build up of transformation products and/or toxic microbial byproducts (closed system), d) different microbial communities both in terms of species (air-dried soil vs. autoclaved-inoculated soil) and numbers (10s vs. 108), and e) input of p-coumaric acid (53 pg/mL/h or 187 pg/h vs. 58 pg/mL one time addition) added to different amounts of soil (60 g of soil for the flow-through system vs. 1 g of soil for the test tube system). 

Natural particles suspended in the air can be transported to regions far from their sources. This is important for transporting many metals and metalloids in the ecosystem. A few metals and metalloids, most notably Hg, As, and Se, can exist not only in the solid and liquid phases but also as gases in ambient environments. The loss of Hg from the aqueous phase can result from reduction of Hg " " to Hg and alkylation to form methyl- or dimethylmercury. Through microbial activity, the methylated forms can be converted to Hg, which is more volatile and less toxic. Microbial mediation can also transform several other trace elements (e.g., As, Se) to organometallic compounds (Gadd, 1993). These volatile organometallic compounds can dominate the transport of these trace elements in local environments. However, bacterial mediation of alkylation of metals such as Hg is influenced substantially by Hg speciation. Mineral colloids vary in their ability to affect the bioavailability and methylation of Hg(II) in aqueous systems... 

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