CHARACTERIZATION OF A MYCOBACTERIUM-SMEGMATIS GENE THAT CONFERS RESISTANCE TO PHAGES L5 AND D29 WHEN OVEREXPRESSED

Bacteriophage infection requires a specific interaction with the outer surface of a bacterial host followed by interaction with the cell mem brane and phage DNA injection. Phages of the mycobacteria encounter a cell wall that is rich in unusual lipid- and sugar-containing componen ts which form a formidable barrier that must be passed to gain access to the membrane. We describe here a gene of Mycobacterium smegmatis th at confers resistance to mycobacteriophages L5 and D29. The phage-resi stance phenotype results not from mutation but from elevated expressio n of a wild-type gene. It appears that the product of this multicopy p hage-resistance (mpr) gene may alter the structure of the host cell wa ll or membrane, thereby inhibiting productive phage DNA injection.