title: Aerobic degradation of di- and trichlorobenzenes by two bacteria isolated from polluted tropical soils.
abstract: Two polychlorinated biphenyl (PCBs)-degrading bacteria were isolated by traditional enrichment technique from electrical transformer fluid (Askarel)-contaminated soils in Lagos, Nigeria. They were classified and identified as Enterobacter sp. SA-2 and Pseudomonas sp. SA-6 on the basis of 16S rRNA gene analysis, in addition to standard cultural and biochemical techniques. The strains were able to grow extensively on dichloro- and trichlorobenzenes. Although they failed to grow on tetrachlorobenzenes, monochloro- and dichlorobenzoic acids, they were able to utilize all monochlorobiphenyls, and some dichlorobiphenyls as sole sources of carbon and energy. The effect of incubation with axenic cultures on the degradation of 0.9 mM 1,4-dichlorobenzene, 0.44 mM 1,2,3- and 0.43 mM 1,3,5-trichlorobenzene in mineral salts medium was studied. Approximately, 80-90% of these xenobiotics were degraded in 200 h, concomitant with cell increase of up to three orders of magnitude, while generation times ranged significantly (P<0.05) from 17-32 h. Catechol 1,2-dioxygenase and catechol 2,3-dioxygenase activities were detected in crude cell-free extracts of cultures pre-grown with benzoate, with the latter enzyme exhibiting a slightly higher activity (0.15-0.17 micromolmin(-1) mg of protein(-1)) with catechol, suggesting that the meta-cleavage pathway is the most readily available catabolic route in the SA strains. The wider substrate specificity of these tropical isolates may help in assessing natural detoxification processes and in designing bioremediation and bioaugmentation methods.
authors.affiliation: Department of Botany and Microbiology, University of Lagos, Lagos, Nigeria.
authors.forename: Sunday A
authors.initials: SA
authors.lastname: Adebusoye
authors.forename: Flynn W
authors.initials: FW
authors.lastname: Picardal
authors.forename: Matthew O
authors.initials: MO
authors.lastname: Ilori
authors.forename: Olukayode O
authors.initials: OO
authors.lastname: Amund
authors.forename: Clay
authors.initials: C
authors.lastname: Fuqua
authors.forename: Nathan
authors.initials: N
authors.lastname: Grindle
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002722:Chlorobenzenes / Q000737:chemistry* / Q000378:metabolism; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism
chemical_list: D002722:Chlorobenzenes; D012989:Soil Pollutants; C036720:trichlorobenzene