Anaerobic growth of Rhodopseudomonas palustris on 4-hydroxybenzoate is dependent on AadR, a member of the cyclic AMP receptor protein family of transcriptional regulators.
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.
Dispensa
M
M
Department of Microbiology, University of Iowa, Iowa City 52242.
Thomas
C T
CT
Kim
M K
MK
Perrotta
J A
JA
Gibson
J
J
Harwood
C S
CS
D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001426:Bacterial Proteins; D001483:Base Sequence; D001565:Benzoates / Q000378:metabolism*; D019817:Benzoic Acid; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010226:Parabens / Q000378:metabolism; D011953:Receptors, Cyclic AMP / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping; D012241:Rhodopseudomonas / Q000235:genetics* / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D001565:Benzoates; D010226:Parabens; D011953:Receptors, Cyclic AMP; D014157:Transcription Factors; C076607:AadR protein, Rhodopseudomonas palustris; D019817:Benzoic Acid; C038193:4-hydroxybenzoic acid