Biology Projects

Title: The role of stress on tetrodotoxin production in rough-skinned newts (Taricha granulosa)

Newts of the genus Taricha have tetrodotoxin (TTX) in the glands of their skin, which is used to defend them from predation.  Tetrodotoxin is a small neurotoxin, that is most well known in puffer-fish, but is found in a wide array of other species.  Much is known about TTX in these species, but very little is known about the physiological constraints of TTX production by these species.  Stress has been shown to impact toxin/venom production in other species due to energetic costs, so it seems likely that this will also be the case in newts.  Students will learn to extract and quantify the stress hormone corticosterone in rough-skinned newts.  Further, students will learn to extract and quantify TTX in the tissues of newts.  This project will give students experience with basic lab skills like pipetting, as well as immunoassays and solid phase extraction as means of quantifying chemicals in the lab. 


Title: Do bacteria found on the skin of the Pacific tree frog (Pseudacris regilla) play a role in protecting the frogs from fungal disease?

Chytridiomycosis, a disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is causing a major decline in amphibian populations worldwide. Interestingly, some species will survive and co-exist in the presence of Bd. Our previous research reveals that bacteria associated with the skin of the North American Bull frog (Lithobates catesbeianus) and the California toad (Anaxyrus boreas halophilus) secrete antifungal compounds, which may play a role in protecting their host. We have also observed that in the Southern San Joaquin Valley, the Pacific tree frog (Pseudacris regilla) is thriving despite the presence of this invasive pathogen. The success of the Pacific tree frog may be attributed to the commensal bacteria living on their skin. Given that for humans and other animals, skin acts as the first barrier of defense, we hypothesize that the bacteria found on the skin of the Pacific tree frog will inhibit the growth of Bd. Furthermore, we hypothesize that the cutaneous bacteria may inhibit the growth of known amphibian and human pathogens. This project aims to identify each bacterial isolate that demonstrates antifungal properties by using DNA sequence analysis, and examining the diversity of cutaneous antifungal microbes. Antifungal bacterial isolates detected in this project may have the potential to widely impact global amphibian conservation and but more importantly their metabolites might be useful for novel chemotherapeutics to combat human diseases.