Identification of three cytotoxic early proteins of mycobacteriophage L5 leading to growth inhibition in Mycobacterium smegmatis.

The article presents a study which shows that the temperate mycobacteriophage L5 produces toxic proteins leading to growth inhibition of the natural host Mycobacterium smegmatis. According to the study, ORFs encoding the toxic gene products are located in the right arm of the phage genome, that primarily codes for regulatory proteins like DNA helicase, primase and repressor. The study shows that the finding that a temperate phage expresses early toxic proteins is remarkable and difficult to interpret, particularly since the closest relative to L5, mycobacteriophage D29, a lytic phage with high sequence similarity and a shared host range, lacks these early genes and the repressor gene.