Acquisition of the ability for Rhodopseudomonas palustris to degrade chlorinated benzoic acids as the sole carbon source

Three strains of Rhodopseudomonas palustris were isolated from phototrophic enrichment cultures containing 3-chlorobenzoate (3-CBA) and benzoate (BA). These new strains as well as several previously described strains of R. palustris were tested in this study and shown to degrade 3-CBA if grown in media that contained BA as a co-substrate. All of the pure cultures that originally required BA for the degradation of 3-CBA acquired the ability to degrade 3-CBA as the sole carbon source after long periods of incubation that ranged from 1 to 3 months. After this adaptation period, the 3-CBA-degrading capabilities of all variants were stable, and the rates of 3-CBA degradation were significantly enhanced as compared to the parental strains. Furthermore, the variants had also acquired the ability to metabolize 2and 4-CBA as sole carbon sources indicating that the enhanced ability to metabolize 3-CBA was accompanied by an expanded ability to metabolize chlorinated benzoates. These data indicate that acquisition of the ability to degrade 3-CBA may be rather common among strains of R. palustris and mutations that confer the ability to metabolize 3-CBA may provide a selective advantage to R. palustris under specific environmental conditions. ß 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.