A peptidoglycan hydrolase similar to bacteriophage endolysins acts as an autolysin in Neisseria gonorrhoeae

We have identified a gene encoding an autolysin (atlA) from Neisseria gonorrhoeae. The deduced amino acid sequence of AtlA shows significant similarity to the peptidoglycan degrading transglycosylases (endolysins) of bacteriophages lambda and P2, suggesting that the encoded protein also functions in peptidoglycan hydrolysis. An atlA mutant was identical to the wild-type strain in exponential growth rate, but demonstrated reduced lysis and peptidoglycan turnover in the stationary phase of growth. When transferred into a buffer solution, at a pH non-permissive for other gonococcal autolysins, an autolytic activity was detectable in the wild-type strain that was not present in the mutant. The most dramatic phenotype of the mutant occurred after extended time in stationary phase. After approximately 16h in stationary phase, both strains underwent an apparent replication event, after which the wild-type strain died rapidly whereas the atlA mutant survived considerably longer. Even after both the wild-type and mutant cells were dead, many of the mutant cells maintained intact morphology, whereas the wild-type cells were lysed. These results suggest that AtlA is a peptidoglycan transglycosylase related to bacteriophage endolysins and acts as an autolysin in the stationary phase.