A high yielding mutant of mycobacteriophage L1 and its application as a diagnostic tool

L1 is a lysogenic phage of mycobacteria, which along with L5 and D29 consti tute a closely linked family of homoimmune mycobacteriophages. These phages can be potentially used for genetic engineering of mycobacteria and diagno sis of mycobacterial infection. The effectiveness; of such phage based syst ems depends on the efficiency with which they infect and grow within target cells. While working with phage L1c1ts which is a temperature sensitive mu tant of phage L1, we observed that high yielding phage stocks were generate d by repeated passage through the host, Mycobacterium smegmatis. A plaque p urified mutant L1-P2, obtained from one such high yielding stock, when anal yzed further was found to infect host cells with increased efficiency. The DNA obtained from L1-P2. was examined by restriction digestion, and it was observed that spontaneous loss of DNA fragment from the right arm, which en codes early regulatory factors, had occurred. It has been further demonstra ted that the high yielding property of the mutant phage could be utilized t o increase the sensitivity of mycobacteriophage-based detection systems. (C ) 2000 Federation of European Microbiological Societies. Published by Elsev ier Science B.V. All rights reserved.