Mycobacteriophage TM4: genome structure and gene expression.

Mycobacteriophage TM4 is a dsDNA-tailed phage that infects both fast-growing and slow-growing strains of mycobacteria. While TM4 has been used extensively for the construction of mycobacterial shuttle phasmids and for the delivery of reporter genes and transposons into mycobacterial cells, little is known about its genetics or molecular biology. We describe here the complete 52,797 bp genome sequence of TM4 and a map of its genome organization. While not a close relative of other mycobacteriophages, TM4 encodes several proteins with sequence similarity to those of other bacteriophages--including L5 and D29--indicating that they have common ancestry. In addition, TM4 encodes proteins with similarity to haloperoxidases, glutaredoxins and the WhiB family of transcriptional regulators. Following infection, TM4 genes are expressed in a defined temporal pattern, with the virion structural proteins expressed late in the phage growth cycle. Understanding the genetics of TM4 will greatly facilitate its use as a tool for the genetic manipulation of the mycobacteria.