Topology of the Bacillus subtilis SpoIISA protein and its role in toxin-antitoxin function.

SpoIISAB is a toxin-antitoxin module encoded on the chromosomes of Bacillus subtilis and related Bacilli species. The SpoIISA toxin was previously shown to target the cytoplasmic membrane and to induce lysis in both B. subtilis and Escherichia coli; however, the precise manner of SpoIISA toxicity remains unknown.

The structure and interactions of SpoIISA and SpoIISB, a toxin-antitoxin system in Bacillus subtilis.

Spore formation in Bacillus subtilis begins with an asymmetric cell division, following which differential gene expression is established by alternative compartment-specific RNA polymerase σ factors. The spoIISAB operon of B. subtilis was identified as a locus whose mutation leads to increased activity of the first sporulation-specific sigma factor, σ(F).

Expression and localization of SpoIISA toxin during the life cycle of Bacillus subtilis.

The previously identified spoIIS locus encodes a toxin-antitoxin system in Bacillus subtilis. It comprises two genes, spoIISA encoding a toxin and spoIISB encoding an antitoxin, which lies adjacent to each other on the chromosome. Each of the spoIIS coding sequences is preceded by a promoter region and the two genes together constitute an operon.

Expression of functional Bacillus SpoIISAB toxin-antitoxin modules in Escherichia coli.

SpoIISA and SpoIISB proteins from Bacillus subtilis belong to a recently described bacterial programmed-cell death system. The current work demonstrates that the toxin-antitoxin module is also functional in Escherichia coli cells, where the expression of SpoIISA toxin leads to transient growth arrest coupled with cell lysis, and SpoIISA-induced death can be prevented by coexpression of its cognate antitoxin, SpoIISB. Escherichia coli cells appear to be able to escape the SpoIISA killing by activation of a specific, as yet unidentified protease that cleaves out the cytosolic part of the protein.