Cutaneous Microbial Antibiosis in the Salamander Ensatina e. klauberi

Overview

Objectives/Goals The objective is to determine if bacteria on the skin of the salamander Ensatina eschscholtzii klauberi produce compounds (antibiotics) that inhibit the growth of microbes from the soil and leaf litter found in the salamander's terrestrial habitat. Methods/Materials Bacterial flora was sampled from 4 wild Ensatina found at two sites on Mt. Palomar (San Diego Co Calif.). Three of the samples came from specimens found at Cedar Creek. The fourth sample came from a specimen found in Doane Valley. The leaf and soil sample was also taken from Doane Valley. The resulting mixed samples where grown in sterilized Petri Dishes. Morphologically distinct bacteria colonies where then isolated so that pure cultures were obtained. Using a microscope, the cellular morphology of each isolate was noted. Ensatina skin bacteria were tested for inhibitory activity against soil bacteria in Inhibition Trials. Inhibition was measured as a zone of unobservable growth adjacent to the bacterial streak. Results The inhibition trials did not demonstrate the presence of bacteria from the skin of Ensatina capable of inhibiting microbial growth from the soil and leaf litter. Unexpectedly, one of the soil bacteria from Doane Valley produced antibiotics that killed off 79% of the bacteria isolated from Cedar Creek Ensatina. However, 100% of the "native" Ensatina bacteria from Doane Valley where unaffected when exposed. Conclusions/Discussion More work is necessary to understand the relation of bacteria to the salamander Ensatina e. klauberi. The study neither refutes nor confirms the presence of cutaneous microbial antibiosis in the salamander Ensatina e. klauberi. Work in the area is vitally and rapidly important because if the role of symbiotic bacteria is found to be significant, removal of them due to pollution may account for many of the current amphibian declines. An "error" in sampling of soil and Ensatina bacteria between two sites on Mount Palomar led to the discovery that the microbial communities of the mountain have evolved a "finely tuned system" of relative stasis. In each case, bacteria have evolved a resistance to antibiotics produce by forms in their native area.

Competition history

• CSEF 2003 Microbiology · Entry S1311

Resources

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