Mechanisms of reverse transcriptase mediated phage resistance in Enterobacteriaceae - PROJECT SUMMARY
Intestinal colonization by multidrug-resistant (MDR) Enterobacteriaceae represents an urgent public
health threat, promoting the dissemination of antimicrobial resistance mechanisms and leading to severe and
often lethal infections. Multiple avenues of protection exist in the gut to defend against potentially pathogenic
organisms, with bacteriophages constituting a crucial node of control over bacterial invasion and expansion.
However, given that bacteria encode a variety of defense pathways to ward off phage predation, the activity of
phage defense systems may serve an essential role in modulating the colonization potential and pathogenicity
of intestinal microbes. The investigation of phage defense mechanisms and their roles in bacterial pathogenesis
is therefore critical for understanding the proliferation of MDR Enterobacteriaceae in the context of the intestinal
microbiome. Additionally, detailed study of phage defense systems has the potential to guide the engineering of
phages as alternatives to antibiotic treatment, an emerging strategy that is already showing considerable promise
in the treatment of MDR infections.
A group of reverse transcriptase (RT) genes that is broadly represented in Enterobacteriaceae has
recently been discovered to function in phage defense. However, the mechanistic link between their RNA-
templated DNA synthesis activity and antiphage immunity remains puzzling. This proposal aims to investigate
the functions of defense-associated RTs (DRTs) in phage defense, and evaluate their contributions to the
pathogenicity of intestinal microbes. Aim 1 will focus on the development of an unbiased experimental approach
for discovering the in vivo RNA substrates and cDNA products of RTs, and will apply this approach to study
diverse DRT systems. Aim 2 will utilize biochemical and genetics assays to determine the minimal components
underlying DRT activity. Aim 3 will leverage a combination of genetic screening and in vivo bacterial pathogenesis
modeling to investigate how dynamic interactions between phages and DRTs modulate the pathogenicity of
Enterobacteriaceae. In addition to illuminating mechanistic features of a compelling new group of phage defense
systems, and linking the activity of these systems to colonization and proliferation of pathogenic bacteria, this
work has the potential to guide future strategies for the prevention and treatment of antibiotic-resistant infections.
This fellowship will support the candidate’s training in the MD/PhD program at Columbia University, which
includes thesis work in the laboratory of Dr. Samuel Sternberg and the remainder of medical training in the
Vagelos College of Physicians and Surgeons. The combination of rigorous scientific training, clinical exposure,
and career development guidance outlined in the proposal will prepare the candidate for a successful career as
an independent investigator and physician-scientist.
