Identification and characterization of an essential gene inListeria monocytogenesusing an inducible gene expression system

The Listeria monocytogenes gene lmo1594 is a homolog of the Bacillus subtilis cell division gene ezrA. EzrA is a negative regulator of FtsZ ring formation, which is required for efficient cell division as it regulates the frequency and position of Z-rings in the cell and prevents aberrant polar cell division. Previously identified as a putative high pressure (HP) resistance mechanism; conferring enhanced barotolerance when heterologously expressed against an Escherichia coli background; the aim of the current study was to investigate whether lmo1594 plays a role in listerial barotolerance. When the creation of a deletion mutant proved unsuccessful, the role of lmo1594 was addressed by creating a conditional knockout mutant which demonstrated that the gene is in fact essential for cell survival and growth in L. monocytogenes. In order to investigate the effect of lmo1594 on barotolerance, the gene was over-expressed. The over-expression of lmo1594 increased survival levels in L. monocytogenes treated at 300 MPa, but survival levels similar to those of the wild-type strain were observed when treated at a higher pressure (≥400 MPa). In conclusion, this study reveals for the first time that lmo1594 is absolutely essential for listerial cell growth and survival, and also plays an important role in listerial barotolerance.