The iap gene of Listeria monocytogenes is essential for cell viability, and its gene product, p60, has bacteriolytic activity

Spontaneous mutants of Listeria monocytogenes have reduced expression of the p60 extracellular protein, leading to rough colony morphology and formation of long chains of cells separated by double septa. The cell-chain-shortening activity of p60, which is encoded by iap, was investigated. The results showed that increased expression of iap leads to shortening of cell chains, and under certain conditions, p60 exhibits bacteriolytic activity. Furthermore, inactivation of iap led to loss of cell viability. It is proposed that p60 is a murein hydrolase which is essential for cell division.