QUORUM SENSING BETWEEN VIBRIO FISCHERI POPULATIONS WITHIN THE SQUID LIGHT ORGAN

Open Access
Author:
Murtha, Andrew
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Timothy Iwao Miyashiro, Thesis Supervisor
  • Ming Tien, Honors Advisor
Keywords:
  • Vibrio
  • quorum sening
  • bioluminescence
  • host-microbe symbiosis
Abstract:
Bacteria impact that health and development of host organisms, and disruption of these interactions can have adverse effects on host fitness. Microbes acquired from the environment must adapt to host conditions in order to survive and remain colonized. This is often achieved through modifications in cellular physiology, such as the production of biofilms or induction of motility. Changes in bacterial gene expression regulate these processes, often times through a process known as quorum sensing. Quorum sensing describes a signaling mechanism that coordinates behaviors among bacterial cells. Vibrio fischeri is a bacterium that colonizes specific sites within the light organ of the Hawaiian bobtail squid, where the resulting populations produce bioluminescence via quorum sensing. This light production is necessary for maintenance of the symbiosis, as non-luminous strains of V. fischeri become attenuated within the light organ. The goal of this work was to investigate how quorum sensing impacts the ability of V. fischeri to maintain symbiosis with the squid. First, the physiology of a natural isolate of V. fischeri was studied. This isolate was taken from an adult squid, meaning that it has persisted over the lifetime of the animal. Then, the impact of luminescence on growth in vitro was tested. This was necessary to determine if effects observed in vivo were related to growth rate. Finally, the impact of quorum sensing on maintenance of the symbiosis was directly measured. This work has found that quorum sensing is necessary for the maintenance of V. fischeri in the Hawaiian bobtail squid.