Phage mobilization and microbiota dynamics driving colonization resistance to Vibrio cholerae invasion - 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.
