of di- and trichlorobenzenes by two bacteria isolated
from polluted tropical soils
Sunday A. Adebusoyea, Flynn W. Picardalb,*,
Matthew O. Iloria, Olukayode O. Amunda
, Clay Fuquac, Nathan Grindlec
Department of Environmental Engineering and Science, Clemson
University, Clemson, SC 29634-0919, USA.
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
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
Keywords: Aerobic biodegradation, Soil pollutants,
Chlorobenzene, Enterobacter sp,Bioremediation,polychlorinated
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