|Solaiman, Daniel - Dan|
Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2005
Publication Date: 2/1/2005
Citation: Solaiman, D., Catara, V., Greco, S. 2005. Poly(hydroxyalkanoate) synthase genotype and pha production of pseudomonas corrugata and p. mediterranea. Journal of Industrial Microbiology and Biotechnology. 32(2):75-82. Interpretive Summary: Poly(hydroxyalkanoates) (PHAs) are bioplastics produced by many different bacteria. There is a need to find new bacteria that can use inexpensive raw materials (for example, the renewable agricultural fats, oils and coproducts) for cell growth and production of new PHAs. Researchers at ERRC earlier discovered a PHA-producing bacterium called Pseudomonas corrugata (PC). Unlike many other Pseudomonas species, PC can grow at a temperature high enough to melt solid fats when those fats are the raw materials. To lay the groundwork to find more bacteria having more desirable growth and product properties, the ERRC researcher collaborated with an Italian research group that has a large collection of different strains of PC and a closely related bacterium called P. mediterranea (PM). Using methods developed by ERRC researchers, 56 strains of PC and 21 strains of PM were screened to characterize their genes responsible for PHA synthesis. We found that all the PM strains have the same organization of PHA genes (called PHA genotype). Six of the PC strains have a similar (but not identical) PHA genotype to that of the PMs, but the remaining 50 PCs are distinctive from the other two groups. Detailed analysis of their PHA genes showed that they are more than 95% identical to each other. We isolated and analyzed the PHA from one representative strain of each group, and found only slight compositional differences among them. Our research helps narrow down the 77 strains of the collection into three distinct groups with different PHA genotypes. This should greatly facilitate future research to identify among these groups the bacteria most useful for production of PHA from agricultural byproducts.
Technical Abstract: 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 (mcl-) PHA synthase genes, we demonstrated the presence of phaC1 and phaC2 in all P. mediterranea strains tested and in six out of fifty-six strains of P. corrugata screened. The remaining fifty strains of P. corrugata yielded only the phaC2 subgenomic fragment on detection by a combined PCR-restriction endonuclease analysis method or a semi-nested PCR amplification approach. Nucleic-acid sequences of the subgenomic phaC fragments of the representative strains 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%).