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Graduation Term

Summer 2025

Degree Name

Master of Science (MS)

Department

School of Biological Sciences

Committee Chair

Kyle Floyd

Committee Co-Chair

Jan-Ulrik Dahl

Committee Member

Tom Hammond

Abstract

The aquatic bacterium, Vibrio cholerae, causes the gastrointestinal disease cholera, resulting in ~3-5 million reported cases and ~100,000-140,000 deaths annually. The ability to form multicellular biofilms is associated with its environmental survival and persistence. Current circulating pandemic strains of V. cholerae, attach to surfaces using the type IV mannose-sensitive hemagglutinin (MSHA) pilus. Loss of MSHA pili attenuates surface colonization and biofilm formation. Components of the MSHA pilus are encoded within two predicted genetic operons; msh-I (mshHIJKLMNEGF) and msh-II (mshBACDOPQ). However, the function of most msh genes remains to be characterized. Understanding the mechanisms of MSHA pilus biogenesis is key to deciphering the environmental survival of V. cholerae. To this end, I have generated deletions of each msh gene, along with corresponding complementation plasmids. Analysis of MSHA pilus production for each deletion strain via hemagglutinin (HA) assay, demonstrated that msh-I genes mshIJKLEG, and msh-II genes mshACDOP are vital for pilus production. Genes mshH, mshM, mshN, mshF, mshB, and mshQ were observed to still support pilus production either partially or fully, and might play an accessory role in assembly/function. Analysis of major pilin subunit (MshA) protein production via immunoblot, demonstrated similar MshA levels among each deletion mutant (except ΔmshA), suggesting that pilus components are produced but not assembled among the mutants. Currently, studies are underway to directly visualize MSHA pilus production, and biofilm formation utilizing an established flow-cell model amongst these msh deletion strains. These studies will identify genes crucial for MSHA pilus production, aiming to develop strategies to reduce V. cholerae survival in the environment.

Access Type

Thesis-ISU Access Only

DOI

https://doi.org/10.30707/ETD.1763755358.633203

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