Growth on Dichlorobiphenyls with Chlorine Substitution on Each Ring by Bacteria Isolated from Contaminated African Soils.
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Until recently, it was generally believed that the presence of more than one chlorine substituent prevented chlorinated biphenyls from serving as a sole source of carbon and energy for aerobic bacteria. In this study, we report the isolation of three aerobic strains, identified as Enterobacter sp. SA-2, Ralstonia sp. SA-4, and Pseudomonas sp. SA-6 from Nigeria polluted soils, that were able to grow on a wide range of dichlorobiphenyls (diCBs). In addition to growing on all monochlorobiphenyls (monoCBs), the strains were all able to utilize 2,2’-, 2,4’-, and 2,3-diCB as a sole source of carbon and energy. With the exception of strain SA-2, growth was also sustainable on 3,3’-, and 3,5-diCB. Washed benzoate-grown cells were typically able to degrade 68 to 100% of the diCB (100 ppm) within 188 h, concomitant with a cell number increase of up to three orders-of-magnitude and elimination of varying amounts of chloride. In many cases, stoichiometric production of a chlorobenzoate (CBA) as a product was observed. During growth on 2,2’, and 2,4’-diCB, organisms exclusively attacked an o-chlorinated ring resulting in the production of 2-CBA and 4-CBA, respectively. A gradual decline in the concentration of the latter was observed, which suggested that the product was being degraded further. In the case of 2,3-diCB, the unsubstituted ring was preferentially metabolized. Initial diCB degradation rates were greatest for 2,4’-diCB (11.2+0.91 to 30.3+7.8 nmol/min per 109 cells) and lowest for 2,2’-diCB (0.37+0.12 to 2.7+1.2 nmol/min per 109 cells).
Chlorine , Biphenyls , Chlorinated biphenyls , Ralstonia sp. , Enterobacter sp. , Pseudomonas sp.
Adebusoye, et al. (2007). Growth on Dichlorobiphenyls with Chlorine Substitution on Each Ring by Bacteria Isolated from Contaminated African Soils. Applied Microbiology and Biotechnology 74, 484-492.