Project Summary / Abstract
The gut microbiota plays a crucial role in various aspects of host health, including resistance against
pathogen colonization. Phages, viruses that infect bacteria, can impact the composition and function of the gut
microbiota, leading to changes in gene expression, metabolic activity, and/or acquisition of novel traits. Our
research focuses on how phages interact with the gut microbiota and influence infection outcomes, specifically
in the context of Vibrio cholerae (Vc) infection, the causative agent of cholera. We have determined that
differences in gut microbiota-mediated bile metabolism are key factors in personalized outcomes of Vc
infection. As Vc uses bile in the gut to regulate its virulence gene expression during infection. The gut
microbiota, particularly the Bacteroidota, can modify the bile pool via enzymes called bile salt hydrolases
(BSHs), which converts bile acid molecules from those that strongly induce Vc virulence to weakly inducing
forms, thereby disrupting the regulatory cascade of Vc. We have also found that phage infection in
Bacteroidota can lead to significant changes in gene expression, including the repression of a sensory protein
(TspO) that regulates BSH activity, resulting in increased ability to deconjugate bile acids and reduce Vc
colonization. Based on these findings, we hypothesize that phage infections in closely related strains and
species of Bacteroidota lead to conserved changes in gene expression, disrupting Vc colonization through up-
regulation of BSH activity, while other genes regulated by TspO increase vulnerability to Vc competition. To
test our hypotheses, we will (Aim I) track phage mobilization in gut microbes using fluorescent protein
reporters and characterize the effect of phage on BSH activity in new hosts. We will also (Aim II) investigate
the consequences of commensal phage on Vc infection using mutagenesis and co-colonization experiments,
to identify the genetic determinants responsible for Vc antagonism of Bacteroidota without phage. These
studies will provide valuable insights into the role of commensal phages in modifying gut bacterial bile salt
sensing and deconjugation, and contribute to our understanding of how phage-mediated processes can be
harnessed for prophylactic interventions against gastrointestinal pathogens such as V. cholerae. Further
understanding of the interactions between phages and the gut microbiota will enable the development of
strategies to manage and potentially engineer the effects of phage-mediated processes on community
dynamics and host health. Overall, our research sheds light on the complex interplay between phages, gut
microbiota, and host-pathogen interactions in the context of Vc infection, with potential implications for
personalized medicine and interventions against infectious diseases.