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Strict and direct transcriptional repression of the pobA gene by benzoate avoids 4‐hydroxybenzoate degradation in the pollutant degrader bacterium Cupriavidus necator JMP134
Author(s) -
Donoso Raúl A.,
PérezPantoja Danilo,
González Bernardo
Publication year - 2011
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2011.02470.x
Subject(s) - cupriavidus necator , hydroxybenzoate , biology , psychological repression , mutant , biochemistry , transcription (linguistics) , activator (genetics) , bacteria , gene , gene expression , genetics , linguistics , philosophy , polyhydroxyalkanoates
Summary As other environmental bacteria, Cupriavidus necator JMP134 uses benzoate as preferred substrate in mixtures with 4‐hydroxybenzoate, strongly inhibiting its degradation. The mechanism underlying this hierarchical use was studied. A C. necator benA mutant, defective in the first step of benzoate degradation, is unable to metabolize 4‐hydroxybenzoate when benzoate is also included in the medium, indicating that this substrate and not one of its catabolic intermediates is directly triggering repression. Reverse transcription polymerase chain reaction analysis revealed that 4‐hydroxybenzoate 3‐hydroxylase‐encoding pobA transcripts are nearly absent in presence of benzoate and a fusion of pobA promoter to lacZ reporter confirmed that benzoate drastically decreases the transcription of this gene. Expression of pobA driven by a heterologous promoter in C. necator benA mutant, allows growth on 4‐hydroxybenzoate in presence of benzoate, overcoming its repressive effect. In contrast with other bacteria, regulators of benzoate catabolism do not participate in repression of 4‐hydroxybenzoate degradation. Moreover, the effect of benzoate on pobA promoter can be observed in heterologous strains with the sole presence of PobR, the transcriptional activator of pobA gene, indicating that PobR is enough to fully reproduce the phenomenon. This novel mechanism for benzoate repression is probably mediated by direct action of benzoate over PobR.