Reductive, coenzyme A-mediated pathway for 3-chlorobenzoate degradation inthe phototrophic bacterium Rhodopseudomonas palustris

We isolated a strain of Rhodopseudomonas palustris (RCB100) by selective en richment in light on 3-chlorobenzoate to investigate the steps that it uses to accomplish anaerobic dechlorination. Analyses of metabolite pools as we ll as enzyme assays suggest that R. palustris grows on 3-chlorobenzoate by (i) converting it to 3-chlorobenzoyl coenzyme A (3-chlorobenzoyl-CoA), (ii) reductively dehalogenating 3-chlorobenzoyl-CoA to benzoyl-CoA, and (iii) d egrading benzoyl-CoA to acetyl-CoA and carbon dioxide. R. palustris uses 3- chlorabenzoate only as a carbon source and thus incorporates the acetyl-CoA that is produced into cell material. The reductive dechlorination route us ed by R. palustris for 3-chlorobenzoate degradation differs from those prev iously described in that a CoA thioester, rather than an unmodified aromati c acid, is the substrate for complete dehalogenation.