SUMMARY. The aim of current study was to estimate the influence of waaLOS and waaLPS genes deletion on lipopolysaccharide (LPS) synthesis, bacterial motility and stress resistance of bacteria Yersinia enterocolitica 6471/76. Single and double waaL mutants were created by replacing the wild-type alleles in bacterial chromosome for mutant ones. The phenotypes of mutants were visualized by DOC-PAGE gels stained with silver and immunoblot with specific to O-polysaccharide and outer core monoclonal antibodies. Bacterial motility was evaluated by the diameter of the migration zone. Wild type bacteria and mutants were analyzed by bacterial growth curves in a hypertonic medium. Participation of WaaL ligases in resistance to osmotic pressure was found only in case of both ligese genes deletion. Also the YeO3_os_ps mutants showed motility decreasing, which recovered after adding a functionally active gene. Thus, deletion of both waaL ligase genes lead to a drastic reduction in bacterial motility and increase their sensitivity to hypertonic medium that can indirectly characterize biological role of WaaL ligases.
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