Date of Submission

Spring 2013

Academic Program

Biology

Project Advisor 1

Brooke Jude

Abstract/Artist's Statement

Chytridiomycosis is a disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). It has been shown that chytridiomycosis is a leading cause of recent global amphibian extinctions (Skerratt et al. 2007). B. dendrobatidis attacks the keratinized skin cells of amphibians, causing the inhibition of vital regulatory processes, and leading to eventual death. It has been shown that certain bacteria such as Janthinobacteria lividum can inhibit the growth of B. dendrobatidis (Berger et al. 2000). Therefore, J. lividum and other similar bacteria could be used to protect amphibian species through bioaugmentation. It is proposed that the mechanism of protection lies in the bacterial production of violacein, a purple-pigmented secondary metabolite (Harris et al. 2009). More research is needed to confirm that violacein is the precise product that inhibits B. dendrobatidis growth. If it is proven that violacein is indeed the factor responsible for inhibiting B. dendrobatidis, then future bio-control studies can be aimed at creating hyper-violacein producing bacterial mutants to bioaugment B. dendrobatidis-afflicted areas. In this study, I use both environmental isolates of violacein-producing bacteria, and violacein-producing mutants created by transposon mutagenesis to test the B. dendrobatidis-inhibition capacities of the different bacterial strains. I designed a novel chytrid-killing assay, and found that strains that produced more violacein were generally better able to kill B. dendrobatidis than strains that produced a minimal amount or no violacein. In all, purple violacein-producing bacteria and violacein extracts proved successful in killing B. dendrobatidis, whereas non-purple pigmented mutants and isolates did not successfully kill B. dendrobatidis, suggesting that violacein is the compound responsible for the anti-chytrid activity and can indeed be considered for use as a protective agent for amphibians.

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