Characterization of DicB Inhibitory Activity in Cell Division Under Stress Conditions

In most bacteria, their chromosomes contain “cryptic”(or defective) prophages, which have lost genes required for the production of phage progeny. However, bacteria seem to have taken advantage of some cryptic prophage genes, albeit poorly characterized, to play various beneficial roles in bacterial host physiology. In this study, we focus on a cryptic-prophage-encoded small protein, DicB. Previously, we show that DicB interacts with MinC to result in cell division inhibition. By systematically probing DicB’s interaction with MinC using different DicB variants, we reveal that the entire N-terminal region of DicB participates in the interaction. We investigate the role of DicB in different physiological environments by monitoring the growth of E. coli under high salt conditions and in the presence of an acylampicillin antibiotic(Azlocillin). Our results demonstrate that DicB helps E. coli cope with high salt and Azlocillin stresses by impeding cell division. Under alkaline conditions, the inhibitory effect of DicB on E. coli cell division is also enhanced. Taken together, our work has shed further lights on the function of DicB, which has largely remained elusive.