[ODP-164] The repression of antitoxin gene ECs5399 of toxin-antitoxin system in EHEC reduces pathogenicity
Toxin-antitoxin systems are generally found in bacteria. Activation of toxin by inactivation of antitoxin induces growth arrest or cell death, through inhibiting fundamental cellular processes. We found genes coding a novel type II TA system, ECs5400-5399, on the chromosome of EHEC O157 Sakai. Our previous studies showed that the induction of this RNase toxin gene (ECs5400) at high level reduced bacterial growth. At low level induction, growth was not suppressed but the production of virulence factors was reduced though expression of housekeeping genes was not affected. These data suggested the novel role of the toxin-antitoxin system in regulation of gene expression rather than inhibition of cell growth. To confirm this, we created the system that can induce repression of antitoxin but not toxin expression on the chromosome genes. The system was based on the CRISPR interference (CRISPRi) method with inducible nuclease deficient dCas9. Growth of EHEC wild type was not affected when suppression of antitoxin expression was induced, on the other hand, the production of virulence factors and the adherence capacity to human intestinal epithelial cells were reduced by suppressing antitoxin expression. These results indicated that the activation of Toxin alters the gene expression profile rather than arrests the growth or induces the cell death.