Isolation and characterization of a transposon mutant of Pseudomonas fluorescens BM07 enhancing the production of polyhydroxyalkanoic acid but deficient in cold-induced exobiopolymer production

Abstract

Pseudomonas fluorescens BM07 is known to produce cold-induced exobiopolymer, which is mainly composed of water-insoluble hydrophobic polypeptides (up to 85%) and saccharides (8%), by decreasing the culture temperature down to as low as 10 °C. We screened for transposon insertion mutants of P. fluorescens BM07 that were unable to produce the exobiopolymer. Among the eight mutants that showed the deficiency of exobiopolymer and O-lipopolysaccharide, one mutant BM07-59 that had the highest polyhydroxyalkanoates (PHA) production was selected. The transposon inserted gene in BM07-59 was identified as galU. The disruption of the gene galU coded for the putative product, UDP-glucose pyrophosphorylase (GalU), resulted in 1.5-fold more accumulation of PHA compared with the wild-type strain from 70 mM fructose or galactose at 30 °C. Electrophoretic analysis of lipopolysaccharide showed that the mutant lacked the O-antigen lipopolysaccharide bands. The glycosyl composition of the lipopolysaccharide produced by the mutant strain was significantly different from that of the wild-type strain. We suggest that the deletion of galU could be a way to shift carbon flux efficiently from exobiopolymer toward PHA in P. fluorescens BM07. © 2010 Federation of European Microbiological Societies.