Genomic and proteomic portrait of a novel mycobacteriophage SWU2 isolated from China

Phage therapy, especially combination with antibiotics, was revitalized to control the antibiotics resistance. Mycobacteriophage, the phage of mycobacterium with the most notorious Mycobacterium tuberculosis (M. tuberculosis), was intensively explored. A novel mycobacteriophage SWU2 was isolated from a soil sample collected at Nanchang city, Jiangxi province, China, by using Mycolicibacterium smegmatis (M. smegmatis) mc² 155 as the host. Phage morphology and biology were characterized. Phage structure proteins were analyzed by LC-MS/MS. The putative functions of phage proteins and multi-genome comparison were performed with bioinformatics. The transmission electron microscopy result indicated that this phage belongs to Siphoviridae of Caudovirales. Plaques of SWU2 appeared clear but small. In a one-step growth test, we demonstrated that SWU2 had a latent period of 30 min and a logarithmic phase of 120 min. Among the 76 predicted Open Reading Frames (ORFs), 9 ORFs were identified as phage structure proteins of SWU2. The assembled phage genome size is 50,013 bp, with 62.7% of G + C content. SWU2 genome sequence shares 88% identity with Mycobacterium phages HINdeR and Timshel, differing in substitutions, insertions and deletions in SWU2. Phylogenetic tree revealed that SWU2 is grouped into A7 sub-cluster. There are several substitutions, insertions and deletions in SWU2 genome in comparison with close cousin phages HINdeR and Timshel. The new phage adds another dimension of abundance to the mycobacteriophages.