Anaerobic growth of Rhodopseudomonas palustris on 4-hydroxybenzoate is dependent on AadR, a member of the cyclic AMP receptor protein family of transcriptional regulators
Open Access
- 1 September 1992
- journal article
- research article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 174 (18), 5803-5813
- https://doi.org/10.1128/jb.174.18.5803-5813.1992
Abstract
The purple nonsulfur phototrophic bacterium Rhodopseudomonas palustris converts structurally diverse aromatic carboxylic acids, including lignin monomers, to benzoate and 4-hydroxybenzoate under anaerobic conditions. These compounds are then further degraded via aromatic ring-fission pathways. A gene termed aadR, for anaerobic aromatic degradation regulator, was identified by complementation of mutants unable to grow anaerobically on 4-hydroxybenzoate. The deduced amino acid sequence of the aadR product is similar to a family of transcriptional regulators which includes Escherichia coli Fnr and Crp, Pseudomonas aeruginosa Anr, and rhizobial FixK and FixK-like proteins. A mutant with a deletion in aadR failed to grow on 4-hydroxybenzoate under anaerobic conditions and grew very slowly on benzoate. It also did not express aromatic acid-coenzyme A ligase II, an enzyme that catalyzes the first step of 4-hydroxybenzoate degradation, and it was defective in 4-hydroxybenzoate-induced expression of benzoate-coenzyme A ligase. The aadR deletion mutant was unaffected in other aspects of anaerobic growth. It grew normally on nonaromatic carbon sources and also under nitrogen-fixing conditions. In addition, aerobic growth on 4-hydroxybenzoate was indistinguishable from that of the wild type. These results indicate that AadR functions as a transcriptional activator of anaerobic aromatic acid degradation.Keywords
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