[Show abstract][Hide abstract] ABSTRACT: A vast array of structurally diverse aromatic compounds is continually released into the environment due to the decomposition of green plants and as a consequence of human industrial activities. Increasing numbers of bacteria that utilize aromatic compounds in the absence of oxygen have been brought into pure culture in recent years. These include most major metabolic types of anaerobic heterotrophs and acetogenic bacteria. Diverse microbes utilize aromatic compounds for diverse purposes. Chlorinated aromatic compounds can serve as electron acceptors in dehalorespiration. Humic substances serve as electron shuttles to enable the use of inorganic electron acceptors, such as insoluble iron oxides, that are not always easily reduced by microbes. Substituents that are attached to aromatic rings may serve as carbon or energy sources for microbes. Examples include acyl side chains and methyl groups. Finally, aromatic compounds can be completely degraded to serve as carbon and energy sources. Routes by which various types of aromatic compounds, including toluene, ethylbenzene, phenol, benzoate, and dihydroxylated compounds, are degraded have been elucidated in recent years. Biochemical strategies employed by microbes to destabilize the aromatic ring in preparation for degradation have become apparent from this work.
[Show abstract][Hide abstract] ABSTRACT: We isolated a strain of Rhodopseudomonas palustris(RCB100) by selective enrichment in light on 3-chlorobenzoate to investigate the steps that it uses to accomplish anaerobic
dechlorination. Analyses of metabolite pools as well 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) degrading benzoyl-CoA to acetyl-CoA and carbon dioxide.R. palustris uses 3-chlorobenzoate only as a carbon source and thus incorporates the acetyl-CoA that is produced into cell material. The
reductive dechlorination route used by R. palustris for 3-chlorobenzoate degradation differs from those previously described in that a CoA thioester, rather than an unmodified
aromatic acid, is the substrate for complete dehalogenation.