Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology
Christine Dawson - California State University, Bakersfield
Worldwide the amphibian population is greatly suffering due to a deadly fungal pathogen known as Batrachochytrium dendrobatidis (Bd) (Reeder et al. 2012). As amphibians obtain oxygen through their thin layers of skin, Bd infects and thickens it, causing amphibians to suffocate and ultimately die. Prior research reveals that some amphibians may have bacteria on the surface of their skin with antifungal properties, allowing for their overall success against Bd (Harris et al. 2009). In California, the Pacific Chorus frog is thriving despite Bd being present in their environment. I hypothesize that the bacteria found on the amphibians’ skin have antifungal properties that has allowed the amphibian to survive against amphibian pathogens. Furthermore, I hypothesize that the cutaneous amphibian bacteria will inhibit the growth of human pathogens. The human pathogens in question are: Candida albicans (Ca), Cryptococcus neoformans (Cn), Microsporum gypseum (Mg), Epidermophyton Floccosum (Ef), and Trichophyton mentagrophytes (Tm). The hypothesis has been tested by preparing bacterial challenge assays in triplicates with a control against Bd and Basidiobolus ranarum (Br), another known amphibian pathogen, and the human pathogens as well. Bacterial challenge assays were prepared against each fungus. A negative result is considered when the fungus continues to grow despite the presence of the bacterial isolate and a positive result is considered when the fungus ceases growth upon the presence of the bacterial isolate. Controls were used as a basis to compare the challenge assays to. To date, approximately 1% of the bacterial isolates have shown antifungal resistance against Bd and 16% against Br. Also, 67% of the bacterial isolates have inhibited at least one fungus, 22% have inhibited two fungi, and 11% have inhibited three or more fungi; these are including both the environmental and human fungal pathogens. Bacterial isolates that demonstrate antifungal properties were identified by sequencing a portion of the 16S rRNA gene. I identified the bacterial isolates using the following molecular techniques: DNA extraction, PCR, gel electrophoresis, and PCR purification. Our results show that the nineteen bacterial isolates belong to the following genus categories: Bacillus, Stenotrophomona, Ochrobactrum, Chryseobacterium, Curvibacter, Pseudomonas, Microbacterium, and Rhodococcus. Denaturing Gradient Gel Electrophoresis (DGGE) will be done to analyze those bacterial samples that are not able to grow in a laboratory setting. Preliminary results support our hypothesis. Results from this study have the potential to prevent the further decline of the amphibian population. This research is important for the amphibian population to survive pathogenic infection by using isolated compounds, which also may aid in the protection against human fungal pathogens. The identification of new, naturally occurring compounds may increase the livelihood and survival of the amphibian populations over time.
References: Harris R.N., Brucker R.M., Walke J.B., and et al. 2009. Skin microbes on frogs prevent morbidity and mortality caused by a lethal skin fungus. Multidisciplinary Journal of Microbial Ecology 3: 818-824.
Reeder, N. M., A. P. Pessier, and V. T. Vredenburg. 2012. A reservoir species for the emerging amphibian pathogen Batrachochytrium dendrobatidis thrives in a landscape decimated by disease. Plos One 7.
Funder Acknowledgement(s): The author gratefully acknowledges the financial support from NSF under grant HRD-0331537 (CSU-LSAMP). I would also like to thank the Student Research Scholars (SRS) program for the funding of our project.
Faculty Advisor: Kathleen Szick, firstname.lastname@example.org
Role: I have been actively involved in every aspect of the listed research.