Bacillus subtilis EzrA and FtsL synergistically regulate FtsZ ring dynamics during cell division.

Previous work has shown that the Bacillus subtilis EzrA protein directly inhibits FtsZ ring assembly, which is required for normal cell division, and that loss of EzrA results in hyperstabilization of the FtsZ polymer in vivo. Here, it was found that in ezrA-disrupted cells, artificial expression of YneA, which suppresses cell division during the SOS response, and disruption of noc (yyaA), which acts as an effector of nucleoid occlusion, resulted in accumulation of multiple non-constricting FtsZ rings, inhibition of cell division, and synthetic lethality. Overexpression of the essential cell division protein FtsL suppressed the effect of ezrA disruption. FtsL overexpression recovered the delayed FtsZ ring constriction seen in ezrA-disrupted wild-type cells. Conversely, the absence of EzrA caused lethality in cells producing a lower amount of FtsL than wild-type cells. It has previously been reported that FtsL is recruited to the division site during the later stages of cell division, although its exact role is currently unknown. The results of this study suggest that FtsL and EzrA synergistically regulate the FtsZ ring constriction in B. subtilis. Interestingly, FtsL overexpression also suppressed the cell division inhibition due to YneA expression or Noc inactivation in ezrA-disrupted cells.