Biodegradation of trichloroethylene (TCE) by bacterial strain G4 resulted in complete dechlorination of the compound, as indicated by the production of inorganic chloride. A component of the water from which strain G4 was isolated that was required for TCE degradation was identified as phenol. Strain G4 degraded TCE in the presence of chloramphenicol only when preinduced with phenol. Toluene, o-cresol, and m-cresol could replace the phenol requirement. Two of the inducers of TCE metabolism, phenol and toluene, apparently induced the same aromatic degradative pathway that cleaved the aromatic ring by meta fission. Cells induced with either phenol or toluene had similar oxidation rates for several aromatic compounds and had similar levels of catechol-2,3-dioxygenase. The results indicate that one or more enzymes of an inducible pathway for aromatic degradation in strain G4 are responsible for the degradation of TCE.
A Beijerinckia strain designated strain Bl was shown to oxidize benz[a]anthracene after induction with biphenyl, m-xylene, and salicylate. Biotransformation experiments showed that after 14 h a maximum of 56% of the benz[a]anthracene was converted to an isomeric mixture of three o-hydroxypolyaromatic acids. Nuclear magnetic resonance and mass spectral analyses led to the identification of the major metabolite as 1-hydroxy-2-anthranoic acid. Two minor metabolites were also isolated and identified as 2-hydroxy-3-phenanthroic acid and 3-hydroxy-2-phenanthroic acid. Mineralization experiments with [12-14C]benz[ajanthracene led to the formation of '4Co2. These results show that the hydroxy acids can be further oxidized and that at least two rings of the benz[a]anthracene molecule can be degraded.
The toxicity of Kepone to mixed populations of estuarine microorganisms was determined by standard plate assays on Zobell marine medium containing 0.02, 0.20, and 2.0 mg of Kepone per liter. Under aerobic conditions, Kepone reduced the number of colony-forming units at all concentrations tested, but had no effect on the number of anaerobic microorganisms. Gram-positive organisms were more sensitive to Kepone than were gram-negative organisms. Growth of gramnegative isolates was not inhibited in nutrient broth, but was significantly inhibited in a minimal salts broth. Oxygen uptake by most isolates was reduced 25 to 100% by 20 ppm (20 mg/ml) of Kepone. Oxygen evolution was observed when several gram-positive isolates were exposed to Kepone concentrations of 20 ppm. Pentachlorophenol at concentrations above 28 ppm produced effects similar to those produced by Kepone. Inhibition of electron transport by Kepone was demonstrated by a significant reduction in the specific activities of NADH oxidases and succinooxidase.
Carbon is distributed in the environment in a variety of chemical compounds that range from gases (methane and carbon dioxide) to liquids (benzene and toluene) to solids (simple sugars and polymers such as cellulose, and asphaltic components of crude o i l ) . The biological degradation of many of these compounds is a naturally occurring reaction. The rate of this reaction, however, is highly dependent on a variety of factors including the specific stmcture of the compound; the availability of nutrients, oxygen, and water for the microorganisms; and the nature of soil or other matrix in which the compound resides. In some cases, certain compounds can be biologically degraded in hours, while other compounds, such as asphaltics, are virtually totally nondegradable.
<=AEMIcAz. STRUCTURE OF PETROLEUM PRODUCISThe susceptibility of petroleum products to biodegradation varies with the types and sizes of the component molecules. Since there are several hundred individual component molecules in any given crude oil, which can vary with its origii, the rate and extent of degradation is not easily predictable. Thus, the overall degradabdity of a specific petroleum product will depend on the proportion of degradable compounds of which it 1s REMBDIATION/AUIUMN 1991 373 Joim C. Cram Wuruhi R lMAHAppBp T m M. W~l~~o c r
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.