CONSTRUCTING AND STUDYING OF THE PROPERTIES OF Francisella tularensis 15 NIIEG VARIANTS WITH REDUCED EXPRESSION OF sodB GENE ENCODING Fe-SUPEROXIDE DISMUTASE

Abstract

Within the frames of the investigation on constructing of an improved live tularemia vaccine with less reactogenicity by the method of allelic replacement using a suicidal plasmid pGM5, the mutant variants have been obtained from the vaccine strain Francisella tularensis 15 NIIEG with a reduced expression of the superoxide dismutase sodB gene. This reduction was a result of the substitution of rare for frequent natural codons in the F e-superoxide dismutase (FeSOD) gene. It was shown that the decrease in the FeSOD production up to 30% of the level in the original strain had no negative effect on the rate of the tularemia cause reproduction. It was shown that the mutant strains were more sensitive to hydrogen peroxide and paraquat as compared to the vacci- he bacteria. All the strains were shown (by Q-PCR) to have at the log phase the elevated content of gene groEL mRNA encoding GroEL chaperone.