REGULATION OF THE PHA GENES IN PSEUDOMONAS PUTIDA KT2440: INVOLVEMENT OF THE STATIONARY PHASE SIGMA FACTOR, sS, AND PUTATIVE TETR-TYPE TRANSCRIPTIONAL REGULATOR PHAD

LAURA RAIGER IUSTMAN; PAULA TRIBELLI; MARTINIANO RICARDI; JIMENA RUIZ

Córdoba

Congreso; VI Congreso Argentino de Microbiología General Sociedad Argentina de Microbiología General; 2009

Sociedad Argentina de Microbiología General

Pseudopmonas putida KT2440 synthesizes and accumulates medium-chain-length polyhydroxyalkanoates (PHA) under conditions of nutrient limitation and carbon excess. The pha locus of P. putida KT2440 consist of seven genes: two PHA polymerases: phaC1 and phaC2, a PHA depolymerase: phaZ, a putative transcriptional regulator of the TetR family: phaD and two PHA granule- associated proteins: phaI and phaF Previous result from our group (Raiger and Ruiz, 2008) demonstrate that the global regulator sigma S affect negatively the expression of the pC1 promoter. Since RpoS is a sigma factor, and a negative regulation by a direct action of a sigma factor is not a common mechanism, we suggested that there must be other regulator acting on pC1 promoter. In this work we showed by Real time PCR that in wild type strain the expression of phaD gene is about 11 fold than the obtained from an rpoS mutant, showing a positive regulation of this gene by the RpoS global regulator. On the other hand, an over-expression of phaD gene in a P. putida KT2440 that contain a pC1:lacZ fusion in the chromosome, shows a significant reduction, five fold, of the β galactosidase expression than the control. These results would indicate that RpoS activates the phaD expression, and PhaD acts as a negative regulator on pC1 promoter. The alternative sigma factor, sigma S, affects polyhydroxyalkanoate (PHA) metabolism in Pseudomonas putida. Laura Raiger Iustman and Jimena Ruiz.(2008). FEMS Microbiol Lett 284: 216-224.