Senior Honors Projects, 2010-current

Date of Award

Spring 2015

Document Type

Dissertation/Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Biology

Advisor(s)

Reid Harris

Eria Rebollar

Abstract

As Malagasy amphibians are facing an impending extinction crisis from the lethal skin fungus Batrachochytrium dendrobatidis (Bd), it has become imperative to proactively mitigate the threat. Bd sporangia develop in the skin of infected amphibians and cause the skin to thicken, leading to ionic imbalance and eventual heart failure. It has been shown that certain bacterial species are able to inhibit Bd growth on amphibians by producing antifungal metabolites. Community-based probiotics are one approach used to combat chytridomycosis by inoculating an environment with Bd-inhibitory bacteria so that many amphibian species are treated at once. With this method, it is important to minimize effects on non-target organisms by selecting anti-Bd bacteria that occur on the amphibians’ skins with the goal of augmenting bacterial abundance. The purpose of this study was to determine which bacteria from an amphibian community at Ranomafana National Park, Madagascar, are capable of inhibiting Bd. To identify anti-Bd bacterial isolates, inhibition assays of each isolate against Bd were conducted. Changes in optical density (492nm) of isolates’ culture filtrates with Bd were compared to controls. After finding which bacteria were positive for inhibition, relationships between the anti-Bd bacterial families, genera, and species and the relative abundances found on each frog species were assessed. Overall, Bd inhibitory isolates were found on every species. Several bacterial isolates were able to inhibit Bd as found in previous studies. However, only two isolates of Sphingobacterium multivorum were identified to inhibit Bd at the species level. Based on this study, I recommend that more research is conducted with greater sample sizes to identify a possible probiotic species that is more commonly found than S. multivorum.

 
 

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