Poly(hydroxyalkanoate) synthase genotype and PHA production of Pseudomonas corrugata and P. mediterranea.

A collection of Pseudomonas corrugata and P. mediterranea strains, two closely related species, was evaluated for the presence and variability of pha loci. Using PCR methods that specifically amplify segments of medium-chain-length poly(hydroxyalkanoate) (mcl-PHA) synthase genes, we demonstrated the presence of phaC1 and phaC2 in all P. mediterranea strains tested and in six out of 56 strains of P. corrugata screened. The remaining 50 strains of P. corrugata yielded only the phaC2 subgene fragment on detection by a combined PCR-restriction endonuclease analysis method or a semi-nested PCR-amplification approach. A Southern hybridization study on a representative strain from this group, however, indicated the presence of the phaC1 gene. Nucleic acid sequences of the subgene phaC fragments of the representative strains from the three groups showed an overall similarity ranging from 95% to 100%. The major repeat-unit monomers of the mcl-PHAs isolated from these selected strains are beta-hydroxyoctanoate (33-47 mol%) and beta-hydroxydecanoate (26-36 mol%). These results differentiate for the first time the strains of P. corrugata into two pha-distinguishable groups. This study also documents for the first time the production of mcl-PHA in P. mediterranea.