Meeting Abstract
Chytrid fungus, Batrachochytrium dendrobatidis (Bd) has been one of the major source of amphibian decline worldwide. This fungus grows and colonizes the keratin layer of the amphibian skin. Different kinds of bacteria inhabit the skin of amphibians, where some of these bacteria can cause inhibition of the activities of Bd. A violacein-producing bacteria (Janthinobacterium lividum) is one of the most studied anti-Bd bacteria but there are Chromobacterium spp that equally produce (a) similar metabolite(s) and have received less study. We identified 4 ribotypes of Chromobacterium (C. sphagnii, C. substugae, C.vaccinii, C. amazonense) isolated from skin swabs of cricket frogs collected from wetlands in the Tuskegee National Forest during several sample periods throughout the year. We tested the violacein-type metabolite produced by each of these 4 ribotypes against three of the most pathogenic strains of Bd at a series of 4 different temperatures (12°C, 16°C, 20°C, 24°C). We hypothesized that the violacein-type metabolites produced by the different ribotypes of Chromobacterium will vary in their ability to inhibit Bd and this variation will be temperature dependent. The bioassay was done using cell-free supernatants from three-day old tryptone broth cultures of each ribotype. When the Bd cultures had reached maximal growth, we challenged each with the supernatants of each of the ribotypes. C. sphagnii exhibited the most inhibitory effect, reducing growth by 60% during the bioassay for three of the Bd strains at 20°C We also observed slow growth of Bd as well as its inhibition at 12°C for all 4 ribotypes. This study shows that these set of violacein-type producing bacteria are also abundant and important in mitigation of Bd infection of amphibians.
