Bacterial Toxin Sets the Course for Infection

Various toxins and effector proteins of bacterial pathogens have been found to manipulate eukaryotic cell machineries to promote persistence and proliferation within their hosts.

Some isolates of Yersinia pseudotuberculosis produce the cytotoxic necrotizing factor (CNFγ), but the functional consequences of this toxin for host-pathogen interactions during the infection are unknown.

Scientists at Helmholtz Center for Infection Research (Brunswick, Germany) cultured Yersinia strains in Luria-Bertani (LB) broth at 25 °C or 37 °C. All DNA manipulations, polymerase chain reactions, restriction digestions, ligations, and transformations were performed using standard techniques. The β-galactosidase activity was determined for three independent cultures of bacteria.

Activation of Ras homolog gene family, member A (RhoA) was tested using the Rho activation assay kit (Millipore; Billerica, MA, USA) and activation of ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 homolog (Cdc42) was determined with the Rho/Rac/Cdc42 Activation Assay Combo Kit (Cell Biolabs; San Diego, CA, USA).

In order to elucidate its function, the scientists genetically modified a bacterial strain that usually forms CNFγ in such a way that it lost the ability to produce this factor. They identified the molecular target that CNFγ manipulates, generating the dramatic consequences that involve the so-called small Rho guanosine triphosphate enzymes (GTPases). These enzymes initiate a whole cascade of events, for example alteration of the cytoskeleton. This leads to pores in the host cell surface, through which bacterial syringes can more efficiently transport active agents into the cell. The observed cell mortality of the immune cells is introduced through Rho GTPases as well.

Petra Dersch, PhD, a professor and senior author of the study explained, “We have discovered a very clever strategy of Yersinia pseudotuberculosis. With the aid of CNFγ, the bacterium manipulates the host cell in such a manner that the injection apparatus can work more effectively. It sets the course for an efficient infection and triggers onset of the disease.” The authors concluded that CNFγ is important for pathogenicity by showing that this toxin modulates inflammatory responses, protects the bacteria from attacks of innate immune effectors and enhances the severity of a Yersinia infection. The study was published on November 7, 2013, in the journal Public Library of Science Pathogens.

Related Links:
Helmholtz Centre for Infection Research
Millipore 
Cell Biolabs