Characterization of fliYfunction and regulation in the squid-vibrio symbiosis

Abstract

The Hawaiian bobtail squid, Euprymna scolopes, forms a symbiosis with the marine bacterium, Vibrio fischeri, in a specialized structure called the light organ. Bacterial transmission in the squid-vibrio symbiosis is horizontal, i.e., juvenile squid hatch from their eggs un-colonized and acquire V. fischeri symbionts from the surrounding seawater. Previous work demonstrated that cysteine auxotrophs of V. fischeri are accommodated within the light organ; however, free cysteine was not detected in the light organ matrix fluid. An alternative mechanism V. fischeri can use to acquire cysteine involves the periplasmic binding protein, FliY, which binds to cystine, the oxidized form of cysteine. Therefore, we hypothesized that FliY allows for the acquisition of host-derived cystine within the light organ. However, a colonization defect was not observed with a ∆fliY mutant, suggesting our initial hypothesis is incorrect. In this study, we also found that the expression of fliY varies among the different populations within the light organ. Culture work has shown that fliY expression is repressed by cysteine and cystine. The results of a transposon mutagenesis screen have suggested that the cysteine biosynthetic pathway activates fliY expression. A regulator of this biosynthetic pathway is the protein CysB. Taken together, our results suggest that some V. fischeri populations within the squid light organ must synthesize cysteine while others receive cysteine in a form different from free cysteine or cystine.

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Work Title Characterization of fliYfunction and regulation in the squid-vibrio symbiosis
Access
Penn State
Creators
  1. Nathan Wasilko
Keyword
  1. Biochemistry and Molecular Biology
  2. Hawaiian bobtail squid
  3. FLiY
  4. quorum-sensing mutant
License Attribution-NonCommercial-NoDerivs 3.0 United States
Work Type Thesis
Acknowledgments
  1. Amie Boal - thesis reader
  2. Tim Miyashiro - research mentor
Publisher
  1. Eberly College of Science
  2. Department of Biochemistry and Molecular Biology
Publication Date Spring 2015
Subject
  1. Biochemistry and Molecular Biology
Language
  1. English
Deposited June 22, 2016

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  • Added 2v692t469c_version1_Nathan_Wasilko_fliY_thesis.pdf
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