Different characteristics between mycobacteriophage Chy1 and D29, which were classified as cluster A2 mycobacteriophages.

ABSTRACT

Purpose: The aim of this study was to isolate a novel mycobacteriophage and then explore its anti‑tuberculosis (TB) potential. Materials and Methods: Phage was isolated from enriched soil sample. A total of 36 mycobacterial strains obtained from clinical specimens were subjected to investigate the host range of phage by the spot lysis assay. Biological characteristics were investigated through growth curve, host range and phage antimicrobial activity in vitro. Then, genome sequencing and further analysis were accomplished by using an ABI3730XL DNA sequencer and comparative genome, respectively. Results: A lytic mycobacteriophage (Chy1) was isolated and the plaque morphology was similar to D29. The genome of Chy1 was estimated to be about 47,198 base pair (bp) and strong similarity (97.4% identity) to D29, especially, the Chy1 gene 7 encoding holin which is considered as a clock controlling growth cycle of the corresponding phage, was identical (100% identity) to phage D29 gene 11, thus classifying Chy1 as a member of the cluster A2 family. However, to our surprise, Chy1 can infect a narrower range of host‑mycobacterial strains than that of D29. The latent period of Chy1 was quite longer compared to D29. Moreover, Chy1 has a weaker ability to lyse Mycobacterium smegmatis compared to D29. Conclusions: The sequence of Chy1 showed 97.4% homology with the genome sequence of D29, but there was a large difference in their biological characteristics. Overall, the results of this investigation indicate that Chy1 is not an ideal candidate for developing mycobacteriophage‑based anti‑TB therapies but for future researches to investigate the reason why biological characteristics of Chy1 and D29 were remarkably different.