Effect of Superoxide Dismutase Gene Inactivation on Virulence of Pseudomonas aeruginosa PAO1 toward the Silkworm, Bombyx mori

• DOI: 10.1128/aem.00981-06
• Publication Date: 2007-01-13T01:35:27Z
• Authors: Kazuhiro Iiyama; Yuuka Chieda; Jae Man Lee; Takahiro Kusakabe; Chisa Yasunaga-Aoki; Susumu Shimizu
• Keywords: 0301 basic medicine; 03 medical and health sciences; Bacterial Proteins; Virulence; Superoxide Dismutase; Mutation; Pseudomonas aeruginosa; Animals; Gene Silencing; Bombyx

ABSTRACT

To investigate the role of superoxide dismutase (SOD) in virulence against the silkworm, Bombyx mori , mutants of Pseudomonas aeruginosa PAO1 lacking manganese-SOD (PAO1 sodM ), iron-SOD (PAO1 sodB ), or both (PAO1 sodMB ) were generated. The mutants were injected into the hemocoel of B. mori . The virulence decreased in the order PAO1 = PAO1 sodM > PAO1 sodB > PAO1 sodMB . In particular, PAO1 sodMB was avirulent at a dose of 10 5 cells or less. The sod double mutant PAO1 sodMB was then complemented with either pSodM or pSodB in trans . In both the complemented strains, the virulence was partially restored. Of the two plasmids, pSodB contributed more to the virulence of P. aeruginosa against B. mori . The results of growth in B. mori hemolymph broth and microscopic analysis suggested that a longer lag phase and superoxide sensitivity correlated with decreased virulence in sod mutants. In conclusion, the SODs are required for full virulence of P. aeruginosa against B. mori and Fe-SOD is more important than Mn-SOD in the infection process.