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Date Permissions Signed

9-13-2018

Date of Award

Fall 2018

Document Type

Masters Thesis

Department or Program Affiliation

Biology

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Brodhagen, Marion (Marion L.)

Second Advisor

Miner, Benjamin G., 1972-

Third Advisor

Donovan, Deborah Anne, 1972-

Abstract

In 2013 sea star wasting disease (SSWD) caused an epizootic in over 20 species of asteroids along the west coast of North America. To see if SSWD was still affecting wild populations, we surveyed populations of the sea star, Pisaster ochraceus, in Birch Bay, WA. Our surveys indicated that advanced symptoms (lesion formation) increased 73% from July to September in 2017. To understand the role of bacteria in SSWD, we isolated bacteria with tissue-degrading potential from epidermal tissues of P. ochraceus animals in Birch Bay, WA. Next, we identified these isolates via 16S rRNA gene sequencing. Our results indicated that the community structure differed between SSWD-affected and healthy stars. In addition, we found that many of the Vibrio species isolated primarily from diseased sea stars lyse red blood cells, avidly degrade gelatin, and are related to species that cause disease in other marine animals. Other researchers have suggested that SSWD is caused by a microbial agent smaller than most bacterial cells (0.2 microns). Although none of the bacteria we isolated were smaller than 0.2 microns, we theorized that their signaling molecules could transmit disease. Quorum sensing signals (QSSs) are bacterially-produced, autoinducing molecules that regulate gene expression in a population-dependent manner within bacterial populations. We hypothesized that quorum sensing signals from diseased animals could facilitate development of SSWD on healthy individuals by triggering expression of virulence genes in opportunistic bacterial pathogens creating a state of dysbiosis. We tested bacterial isolates and tissue extracts from diseased and healthy sea stars for the presence of a subset of QSSs, acyl homoserine lactones (AHLs). We found that organic extracts from healthy and diseased stars differed in how strongly they activated a QSS bioreporter, and that multiple of the bacterial isolates associating with diseased stars produced AHLs. Thus, quorum sensing might contribute to transmission of SSWD.

Type

Text

Keywords

Sea star wasting disease, sea star wasting syndrome, epizootic disease

Publisher

Western Washington University

OCLC Number

1076552186

Subject – LCSH

Pisaster ochraceus--Diseases and pests--Washington (State)--Birch Bay (Bay); Pisaster ochraceus--Pathogens--Washington (State)--Birch Bay (Bay); Chronic wasting disease--Washington (State)--Birch Bay (Bay); Pathogenic bacteria--Washington (State)--Birch Bay (Bay); Quorum sensing (Microbiology)

Geographic Coverage

Birch Bay (Wash. : Bay)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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