Chemotaxis in Vibrio coralliilyticus: deciphering the behavioral dynamicals of a coral pathogen

Author: Karina Winn

Winn, Karina, 2017 Chemotaxis in Vibrio coralliilyticus: deciphering the behavioral dynamicals of a coral pathogen, Flinders University, School of Biological Sciences

Terms of Use: This electronic version is (or will be) made publicly available by Flinders University in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. You may use this material for uses permitted under the Copyright Act 1968. If you are the owner of any included third party copyright material and/or you believe that any material has been made available without permission of the copyright owner please contact with the details.


Microbes are linked to the fitness of coral and are integral players in the health of the entire coral reef ecosystem. Despite an increased awareness of the prevalence and influence microbes have on the decline of reef systems worldwide, there is limited information on the invasion mechanisms possessed by bacteria that initiate pathogenicity. Chemotactic motility and gene expression analysis is thought to yield the most informative and detailed view of bacterial capabilities, greatly increasing our ability to understand the methods, limitations and possibilities of infection. This thesis investigates the capabilities of Vibrio coralliilyticus to orientate through simulated regions of the natural coral holobiont. This determines the extent this pathogen remains motile irrespective of the fluctuations in the structural and chemical integrity of the coral mucus and surrounding seawater including viscosity variability and nutrient availability. The reoccurring theme of this thesis has been that V. coralliilyticus’s chemotactic search paths altered following the viscosity and daily oxygen fluctuations present within the coral organism. Furthermore, this thesis demonstrated that V. coralliilyticus’s 3-step flick search patterns showed a 14 times reduction when entering coral mucus regions presumably driven by the mechanical impediment viscosity has on the rotation of the flagellar motor. In addition, search patterns in the coral mucus exhibited an 11 times increase in energetic cost, in glucose molecules. This thesis provides detailed insight into the behavioral control V. coralliilyticus possess to manipulate and exploit nutrient and chemotactic regions by altering its search pattern run length to elevate its diffusivity values and for the first time, demonstrates that the gene expression of the flaA and flhA gene can be observed to correlate with chemotactic search pattern speed.

Keywords: Vibrio coralliilyticus, coral, pathogen, chemotaxis, motility,

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Biological Sciences
Supervisor: Professor Jim Mitchell