[Study of expression of contact-dependent secretion systems in Vibrio cholerae on the model of Dictyostelium discoideum].

Aim: To detect T3SS and T6SS genes in Vibrio cholerae genomes and assessment of resistance of strains with different genotype characteristics to ingestion by Dictyostelium discoideum amoeba.

Materials And Methods: One hundred thirty-five toxigenic and non-toxigenic strains of Echolerae O1, O139, and non-O1/non-O139 were studied by PCR and on Dictyostelium discoideum model.

Results: T3SS cluster of genes was detected in several non-toxigenic representatives of 01 and non-O1/non-O139 serogroups. All toxigenic vibrios except one strain belonging to non-O1/ non-O139 serogroup lack this cluster. T6SS genes were presented in all studied strains although far from allofthem contained sequence coding ACD-domain of vgrG1 gene product--key effector of T6SS. Susceptibility of vibrios to ingestion by amoeba did not depend from presence of T3SS genes. Only strains with genetic determinants ACD-vgrG1 together with pathogenicity locus VPI were resistant to ingestion, all others were susceptible.

Conclusion: D. discoideum model is adequate for study of expression of T6SS but not T3SS in V. cholerae. The latter is rather needed for colonization of intestine than for antagonistic activity against protozoa in external environment. Expression of T6SS is characteristic for many non-toxigenic strains of V. cholerae, whereas use of contact-dependent secretion is unlikely necessary for majority of toxigenic strains.