Date of Completion

9-7-2019

Embargo Period

9-6-2020

Keywords

squid, symbiosis, cephalopods, innate immunity, development, E. scolopes, Vibrio fischeri, hemocyte

Major Advisor

Spencer V. Nyholm

Associate Advisor

Joerg Graf

Associate Advisor

Nichole Broderick

Associate Advisor

David A. Knecht

Associate Advisor

Michael Lynes and Adam Zweifach

Field of Study

Molecular and Cell Biology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Beneficial associations with microorganisms are widespread in the animal kingdom. The Hawaiian bobtail squid (Euprymna scolopes) has two symbiotic organs with bacteria. The light organ symbiosis contains one species of bioluminescent bacteria, Vibrio fischeri, which produces light allowing the squid to camouflage itself against down-welling moonlight. The second organ, the accessory nidamental gland (ANG), is found only in female squid and houses a consortium of bacteria1. Bacteria from the ANG are deposited into the squid’s egg jelly coat 2, where they play a defensive role against biofouling 3 1,4.

This dissertation characterizes the development of the ANG showing that the nascent ANG develops to recruit bacteria from the environment. . Furthermore, in laboratory culture, ANG tubules do not form and the host is not colonized in the absence of an environmental cue found in substrate from the host’s natural environment. In captivity, ANGs developed by raising squid on sand collected from the host’s natural environment, suggesting that specific bacteria may be required for development.

Immune cells are thought to be important for the maintenance of symbiosis. Live cell microscopy with squid immune cells (hemocytes), revealed that hemocyte-bacteria interactions are partially mediated via bacteria membrane components. These assays identified specific molecules that may play a role in recognition of the symbiont, including an outer membrane porin, OmpU and lipopolysaccharide. This work also showed that long-term colonization by V. fischeri influenced development and maturation of the host hemocyte response specifically to the symbiont.

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