An Auto-Regulating Type II Toxin-Antitoxin System Modulates Drug Resistance and Virulence in .

Toxin-antitoxin (TA) systems are ubiquitous genetic elements that play an essential role in multidrug tolerance and virulence . So far, little is known about the TA systems in . In this study, the Xress-MNTss TA system, composed of the MNTss toxin in the periplasmic space and its interacting Xress antitoxin, was identified in . β-galactosidase activity and electrophoretic mobility shift assay (EMSA) revealed that Xress and the Xress-MNTss complex could bind directly to the Xress-MNTss promoter as well as downregulate streptomycin adenylyltransferase . Interestingly, the Xress deletion mutant was less pathogenic following a challenge in mice. Transmission electron microscopy and adhesion assays pointed to a significantly thinner capsule but greater biofilm-formation capacity in Δ than in the wild-type strain. These results indicate that Xress-MNTss, a new type II TA system, plays an important role in antibiotic resistance and pathogenicity in .