Immunity Protein Protects Gut Bacteria from Cholera Infection

In a study published in Nature Communications, researchers from Ecole Polytechnique Fédérale de Lausanne shared insights on the way V. cholerae interacts with bacteria of the human microbiota. Their findings showed that although several species of gut bacteria are depleted following T6SS-mediated attacks by V. cholerae, a significant subset resist it. Specifically, some Klebsiella gut species shield themselves against the T6SS attacks of V. cholerae with a polysaccharide capsule that is characteristic of encapsulated bacteria.

Because it is a highly efficient killing device, bacteria like V. cholerae that use T6SS also have ways to protect themselves to avoid self-intoxication. To do this, T6SS-using bacteria produce specific immunity proteins that block the toxic effects of the T6SS. But the study found that some members of the human microbiota protect themselves from T6SS attacks without going the immunity-protein route. Specifically, the study showed that E. cloacae—itself an opportunistic pathogen—fight back by actually killing V. cholerae first with its own, superior, T6SS weaponry.

“This work provides us with some new insight into bacterial community behavior within the intestinal microbiota and how defense against T6SS intoxication might help bacterial populations to defend themselves against invading pathogens,” says lead researcher Melanie Blokesch. But she also emphasizes that the study was carried out in vitro, and additional studies are needed if we are to get a more complete picture. 

“Nonetheless, our work could serve as a starting point to rationally design T6SS-shielded probiotic strains that are able to restore defective colonization barriers or enhance the barriers’ efficiency,” the authors conclude.