GLOBAL PROTEOME INVESTIGATION OF MYCOBACTERIOPHAGE OCHI17-MYCOBACTERIUM SMEGMATIS INTERACTIONS

Bacteriophages (phages) have broad applications in diverse areas including phage therapy, agriculture, food safety, and environmental protection. In order to fully realize the potential for phage applications, it is critical to understand phage-bacteria interactions and characterize bacterial responses/targets to phage infection. Previous studies have largely focused on other classes of phages other than mycobacteriophages. This research provides the first global proteome investigation of the dynamic relationship between a mycobacteriophage and a mycobacterial host. Mycobacteriophages are viruses that infect mycobacteria. They have been reported to have vital potential uses in various fields, especially as an alternative in the prevention and treatment of mycobacterial diseases such as tuberculosis. Despite their potential, not much is known about the molecular interaction with mycobacteria during a mycobacteriophage infection, especially at the translational level. To better understand this, a novel mycobacteriophage, Ochi17 was first isolated and characterized based on the genome and structure. I then applied label-free quantitative proteomics using the model host, Mycobacteria smegmatis,which was infected with Ochi17 at different infection time points. Phage Ochi17 was found to be a temperate phage and classified as a Siphoviridae. The proteome changes occurring at the mid-lytic stage of Phage Ochi17 infection was first examined followed by a temporal study of the global changes. More than 2,000 M. smegmatis proteins and at least 50 Ochi17 proteins were identified across all time points. Homologous recombination and host macromolecular synthetic processes were significantly upregulated, while lipid metabolism was significantly downregulated. The results suggested that Ochi17 suppressed the growth of Mycobacterium smegmatis not just by utilizing the macromolecular synthesis of the host, but also by suppressing host transcription, and fatty acid biosynthesis, in addition to the degradation of fatty acids irrespective of infection time. The two-component system was a target at only 24 h post infection. I also showed that phage Ochi17 proteome expression is time-dependent and the proteins typically cluster based on functional relatedness. The results presented here may contribute in the development of mycobacteriophages as antimicrobial therapies that can overcome various defense strategies employed by host mycobacteria.