Lytic Efficiency of Mycobacteriophages

Mycobacteriophages D29 and TM4 are the two virulent phages widely used for the study of mycobacterial genetics. Both the phages are capable of killing Mycobacterium tuberculosis but the efficiency of these phages in killing has not been evaluated and compared. There are reports based on codon usage analysis where TM4 is predicted to be a better killing phage over D29 which corroborated with the whole genome in silico analysis. In addition a kill assay using 5 wild type virulent mycobacteriophages viz. D29, TM4, I3, Che7 and Che11 was performed to study the killing efficiency of these phages using LRP assay. Based on the results, D29 was found to infect all the 10 clinical strains of M. tuberculosis and significantly reduced RLU at 3 hours and this effect continued up to 24 hours. Thus, D29 is found to have better killing efficiency than TM4 contradicting the earlier predictions. In silico analysis of holin and lysin genes of TM4 and D29 substantiated our findings.