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Project Title: Glyphosate Inhibits Keratinolytic Activity of Bacillus spp. Isolated from Wild Songbirds
Mentor: Laura Tuhela-Reuning
Glyphosate is a frequently-used herbicide both domestically and in the agricultural industry worldwide. While the effect of glyphosate ingestion on bird health has been studied, less is known about the potential impact of glyphosate on bacteria found on avian plumage. This study investigated the effect of glyphosate on the degradation of bird feathers by keratinolytic plumage bacteria. To determine the effect of glyphosate on bacterial feather degradation, two strains of Bacillus spp. isolated from the plumage of wild songbirds captured in mist nets were tested. A disk-diffusion assay was used to determine that 8.44 g/L of glyphosate inhibited the growth of these two isolates. Feather degradation assays were subsequently performed on each of the Bacillus isolates to determine whether the keratinolytic activity of the bacteria was affected. For each isolate, four tubes were prepared that contained a basal salts medium and a white goose feather as the sole carbon and nitrogen source. To two of those tubes, 8.44 g/L of glyphosate was added, then one tube with glyphosate and one tube without glyphosate were inoculated with a Bacillus isolate. The other tubes with and without glyphosate were left uninoculated as controls. All experiments were done in replicates of 10, and all tubes were incubated at 37⁰C at 125 rpm for seven days. Aliquots from each tube were removed once every 24 hours. Feather degradation was determined by measuring the absorbance of the aliquots at 230 nm. At this wavelength, an increase in the absorbance indicated an increase in oligopeptides resulting from the degradation of keratin in the feathers. The results from uninoculated tubes indicated that glyphosate alone did not damage feathers. However, glyphosate inhibited bacterial feather degradation from 86% to 98% depending upon the isolate. These data suggest that exposure to glyphosate disrupts feather degradation by Bacillus spp.