loading
loading
NIH grant 1R15GM166965-01: Functional Characterization of Novel Phage Satellites in Mycobacteria
Institute: {'code': 'GM', 'abbreviation': 'NIGMS', 'name': 'National Institute of General Medical Sciences', 'admin_org_id': '12500024', 'admin_funding_url': ''}. PI: MARGARET S SAHA. Award: $571875.
Start: 2026-09-05T00:00:00.
PROJECT SUMMARY
Phage Satellites are mobile genetic elements that depend on helper phage for replication and assembly.
They exist as plasmids, integrated chromosomal elements, or independent infectious particles. Lacking
essential genes, they parasitize helper phage to complete their life cycles, creating dynamic interactions
among host bacteria, helper phages, and satellites. Phage satellites can benefit their bacterial hosts by
conferring immunity to non-helper phages, enhancing virulence, and disrupting helper phage
reproduction. Once overlooked as degraded phage, phage satellites are now recognized as major drivers
of virus–virus interactions, horizontal gene transfer, microbial evolution, and bacterial population
dynamics. They also offer promising applications in biotechnology and phage therapy, however the vast
majority of phage satellites remain unexplored. Only a single instance of a phage satellite has been
identified in the entire Actinobacteria phylum, and none have been reported in Mycobacteria until the
discovery of Extracellular Prophage-Inducing Particles (EPIPs) by our laboratory—the first phage
satellites discovered to infect the Mycobacterium genus. EPIPs consistently trigger excision and
activation of the helper prophage HerbertWM from Mycobacterium aichiense, establishing a novel
satellite–helper system and the first reported in the mycobacterial genus. The overarching goal of this
proposal is to advance fundamental understanding of Mycobacterium phage satellite biology by
delineating patterns of gene expression during infection, determining satellite gene functions through
overexpression and targeted knockouts, and characterizing their host range and prevalence in natural
environments through the following specific aims. Aim 1 will quantify temporal gene expression
dynamics of the host, helper phage, and satellite during infection by performing RNA sequencing and
mass spectrometry-based proteomics at multiple time points following infection with the satellite. Aim 2
will elucidate molecular functions of EPIP-encoded genes through inducible overexpression, targeted
gene knockouts, and integrative structural bioinformatics to predict and test mechanistic roles in
replication, excision, and helper activation. Aim 3 will delineate the host range of EPIPs by testing host
specificity, cross-species mobilization, and prevalence across Mycobacterium and related Actinobacteria
using infection assays, qPCR-based excision tracking, and computational genome mining with satellite
discovery software developed in our laboratory. This project will enhance our understanding of
fundamental principles governing satellite–helper interactions in Actinobacteria and molecular
determinants of viral parasitism. The resulting insights will expand mechanistic understanding of phage
regulation, inform evolutionary models of horizontal gene transfer, and provide a foundation for future
applications in biotechnology, controlling bacterial infections, and phage therapy.document fetched 2026-09-13 02:45