Volume 13, Issue 6 p. 1590-1600

Strict and direct transcriptional repression of the pobA gene by benzoate avoids 4-hydroxybenzoate degradation in the pollutant degrader bacterium Cupriavidus necator JMP134

Raúl A. Donoso

Raúl A. Donoso

Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile

Millennium Nucleus on Plant Functional Genomics, Center for Advanced Studies in Ecology, P. Universidad Católica de Chile, Santiago, Chile

Search for more papers by this author
Danilo Pérez-Pantoja

Danilo Pérez-Pantoja

Millennium Nucleus on Plant Functional Genomics, Center for Advanced Studies in Ecology, P. Universidad Católica de Chile, Santiago, Chile

Search for more papers by this author
Bernardo González

Corresponding Author

Bernardo González

Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile

Millennium Nucleus on Plant Functional Genomics, Center for Advanced Studies in Ecology, P. Universidad Católica de Chile, Santiago, Chile

E-mail [email protected]; Tel. (+56) 2 3311619; Fax (+56) 2 3311906. Search for more papers by this author
First published: 30 March 2011
Citations: 21

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.