Abstract
Abstract Pseudomoas aeruginosa is an important opportunistic pathogen capable of causing acute infections in immunocompromised individuals and chronic infections in cystic fibrosis patients. The galU gene encodes UDP-glucose pyrophosphorylase, which catalyses the reversible formation of UDP-glucose from glucose 1-phosphate and UTP. We have constructed a galU mutant of P. aeruginosa by insertion of kanamycin-resistant-gene cassette through homologous recombination. The mutant strain with the inactivated galU gene was verified by the loss of UDP-glucose pyrophosphorylase activities. Environmental stresses such as acidic pH and hypertonic medium did not affect the growth of the mutant strain. But the mutant strain exhibited increased sensitivity to heat and paraquat, a redox compound inducing intracellular levels of superoxide. An interesting finding is its reduced susceptibility to b-lactam antibiotics. Comparison analysis of the outer membrane protein profiles between the galU mutant and wild type bacterium did not show significant differences except that an 8-kDa protein was found only in the galU mutant. We also observed that the galU mutant was incapable of synthesizing a complete lipopolysaccharide (LPS), which may contribute to the increased serum sensitivity and reduced virulence in neutropenic mice model. The data presented here demonstrated that the galU gene is required for the synthesis of a complete LPS and the defective LPS may result from failing to incorporation of glucose to the core region of LPS.