Streptomyces isolated from bird feathers as a potential source for novel antibiotics

Streptomyces, the main source of antibiotics essential for human health, are widely distributed in nature among terrestrial, oceanic and atmospheric environments. New trends in antibiotic discovery are focused in the search for novel bioactive strains in unexplored habitats. We provide here evidence of the presence of diverse Streptomyces populations in wild bird feathers, such as the seagull, Larus michahellis, collected at Northern Spain; the sparrow, Passer domesticus, and the hoopoe, Upupa epops, both collected in Southern Spain. Taxonomic identification of fourteen bioactive strains, by sequencing their 16S rRNA gene and phylogenetic analyses, revealed that all of them are homologous to a total of 10 different Streptomyces. Strains from seagull samples are homologous to other antibiotic producers previously isolated from atmospheric, marine and terrestrial environments in the Cantabrian Sea region, Northern Spain. Isolates form Southern feather samples, from a house sparrow and a Eurasian hoopoe, are homologues to Streptomyces strains previously isolated mainly from soils along the Mediterranean region. The most relevant feature is that they are producers of diverse antibiotics with activity against Gram-positive, Gram-negative bacteria and fungi. We report here the successful activation of silent antibiotic biosynthetic pathways in response to changes in environmental conditions, such as incubation temperature and salinity of the culture medium, in agreement with the OSMAC approach, One Strain Many Compounds. The finding of bioactive Streptomyces in bird's plumage might be of relevance, not only in the ecology of Streptomyces-birds associations, but also in medicine and biotechnology since they can be regarded as a potential source for novel antibiotics.