Type VI Secretion System Dependent Interactions and Diversity in Vibrio fischeri
Open Access
- Author:
- Moore, Peyton
- Area of Honors:
- Microbiology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Timothy Iwao Miyashiro, Thesis Supervisor
Timothy Charles Meredith, Thesis Honors Advisor - Keywords:
- Vibrio fischeri
Euprymna scolopes
Type VI secretion system
Effectors
Interference competition
Strain diversity
Host-microbe
Symbiosis - Abstract:
- Many animals rely on symbioses with microorganisms for normal development and health. Symbiont populations usually consist of multiple species and/or strains that exhibit diverse traits, and these characteristics impact their fitness for establishing and maintaining symbiosis. These traits include mechanisms that promote interactions between cells, specifically competitive interactions to obtain space and resources within habitats in the host. A gap in knowledge currently exists regarding how diversity in these traits impacts formation of symbiont populations. To address this knowledge gap, this study characterizes a natural isolate of Vibrio fischeri, which is a bacterial symbiont that forms a multi-strain symbiosis with the Hawaiian bobtail squid Euprymna scolopes. This characterization contributes to our understanding of strain diversity within a system. Specifically, we investigate the diversity of a molecular mechanism that promotes interference competition among V. fischeri in the host called the type VI secretion system (T6SS), which is a contact-dependent nanomachine that delivers toxic effectors into neighboring cells. T6SS-positive (T6SS+) cells prevent self-intoxication by co-expressing immunity proteins that neutralize the toxins. How non-isogenic T6SS+ strains interact with each other remains poorly understood, which prevents the ability to predict which strains can coexist within the same habitats. This study showcases diversity among T6SS effectors to highlight factors that potentially influence population organization. We showcase that strains can readily utilize adopted toxins, and foreign toxins from competitor cells can cause inhibition of kin cells, despite harboring immunity proteins. Taken together, these findings support a model in which T6SS+ strains inhibit each other using diverse effectors, which provides insight into how different T6SS+ strains can occupy the same habitat.