title: Growth on dichlorobiphenyls with chlorine substitution on each ring by bacteria isolated from contaminated African soils.
abstract: 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 Nigerian 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 10(9) cells) and lowest for 2,2'-diCB (0.37 +/- 0.12 to 2.7 +/- 1.2 nmol/min per 10(9) cells).
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: D001673:Biodegradation, Environmental; D002713:Chlorine / Q000737:chemistry; D015169:Colony Count, Microbial; D004754:Enterobacter / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D009549:Nigeria; D011078:Polychlorinated Biphenyls / Q000737:chemistry / Q000378:metabolism*; D011549:Pseudomonas / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D043367:Ralstonia / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D012989:Soil Pollutants; D002713:Chlorine; D011078:Polychlorinated Biphenyls