BIO44) Cloning and characterization of polyhydroxyalkanoate (PHA) genes from Pseudomonas sp. isolated from Antarctica

Introduction Pseudomonas strains accumulate mediumchain-length poly(R)-3-hydroxyalkanoate (PHA) as carbon and energy source under conditions of limiting nutrients in the presence of an excess of carbon source (Fidler et al., 1992). This bacterial storage material, mainly formed of monomers of 6 to 14 carbon atoms, has potential as a renewable and biodegradable plastic (Prieto et al., 1999). Most of the research on PHAs was done on well-known PHA-producing soil microorganisms. However, PHA-producing microorganisms from the Arctic or Antarctic regions are still unknown. Psychrophilic bacteria are bacteria normally found in temperate countries. They can survive at low temperature (below 10°C). The psychrophiles are subdivided into obligate and facultative groups. Obligate psychrophiles seldom grow above 22°C and facultative psychrophiles (psychrotrophs) grow very well above 25°C. Several genes such as phaC (PHA synthase), phaA (β-ketothiolase), phaB (NADH-acetoacetyl-CoA reductase), phaG (3-hydroxyacyl-carrier protein-coenzyme A transferase) and phaJ (enoyl-CoA hydratase) are responsible in the accumulation of PHA. An enzyme known as PHA depolymerase coded by phaZ gene will then degrade these PHA compounds (Bernd et al., 1999). The PHA biosynthesis genes are often clustered in the bacterial genome as an operon called phaCAB (Steinbuchel et al., 1992). PHA synthase enzymes can be divided into three types; Type I PHA synthases (R. eutropha) preferentially uses coenzyme A thioesters of various short chain length (3HASCL) comprising three to five carbon atoms, whereas type II PHA synthases (P. aeruginosa) preferentially utilize coenzyme A thioesters of various medium chain length with at least five carbon atoms (3HAMCL). Type III PHA synthases (C. vinosum) prefer coenzyme A thioester of 3HASCL. In this paper, we describe the isolation of a PHAproducing bacterium from Antarctica for pha Synthase gene characterization.