Prevalence of feather-degrading Bacillus spp. on the plumage of birds in Australia

Abstract

<p> Bird plumage hosts a diverse microbial community, including microbes capable of degrading the β-keratin in feathers (i.e. feather-degrading bacteria). The prevalence and effects of feather-degrading bacteria have primarily been studied in the Northern Hemisphere, and knowledge of the occurrence of these bacteria on Southern Hemisphere bird species is lacking. We explored the prevalence of feather-degrading bacteria on wild birds in Australia by sampling feathers from 254 individuals representing 25 species. First, to determine the total plumage bacterial load, we sampled bacteria from three body regions and identified and enumerated three presumed feather-degrading <i>Bacillus</i> spp. (<i>B. licheniformis, B. cereus, and B. subtilis</i>) based on morphology. Second, we collected a feather from each bird and in laboratory tests confirmed the presence of feather-degrading bacteria. Third, we tested for a relationship between the number of presumed feather-degrading <i>Bacillus</i> spp. counted and the presence of feather-degrading bacteria on the following variables: habitat type, foraging behaviour, flocking status, and feather wear. We found 85% of birds sampled harboured presumed <i>Bacillus</i> spp. Of the feather samples that tested positive for <i>Bacillus</i> in lab experiments, 62% were confirmed as feather-degrading <i>Bacillus</i> spp. The total plumage bacterial load varied with habitat type, with birds in heath habitats harbouring fewer bacteria. This study is the first report of feather-degrading bacteria on the plumage of wild Australian birds <i>in vivo</i>.</p>