Regulation of pchP gene in Pseudomonas aeuginosa

MASSIMELLI, MJ; CHOI, KH; BEASSONI, PR; DOMENECH, CE; SCHWEIZER, HP; LISA, AT

Rosario, Argentina

Congreso; XLII Reunión Anual, Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

Taking advantage of the recent identification of the gene encoding for phosphorylcholine phosphatase enzyme, named pchP, we proposed to elucidate the molecular mechanisms governing its expression in P. aeruginosa. We showed that this gene is principally transcribed as a monocistronic mRNA. Consistently, a functional promoter was found in the intergenic region immediately upstream of pchP. b-gal activity measurements showed that pchP promoter is induced by choline and derivatives, and it is shut down by addition of succinate plus ammonium. By fusing different fragments of the pchP upstream region to a promoter-less lacZ reporter gene, the region from –74 to –55 was shown to include the most likely pchP promoter. PA5293, a putative LysR-type regulator-encoding gene, is located usptream of pchP. A deletion mutant of this gene, which will henceforth be called pchT, was constructed. DpchT mutant produced greatly reduced levels of PChP activity in periplasmic extract, but the deletion of this gene did not affect pchP promoter activity. The DpchT mutant also showed up to 8-fold increase in pchP transcription, relative to the wild-type strain, atributed to a constitutive increase of transcription from pchT promoter. This indicates that this LysR regulator is not involved in the regulation of pchP promoter at the transcriptional level, at least not under the conditions employed in this study.