Chicken intestinal mycobiome: Initial characterization and its response to bacitracin methylene disalicylate

The gastrointestinal (GI) tract harbors a diverse population of microorganisms. While much work has been focused on the characterization of the bacterial community, very little is known about the fungal community, or mycobiota, in different animal species and chickens in particular. Here, we characterized the biogeography of the mycobiota along the GI tract of day 28 broiler chicks and further examined its possible shift in response to bacitracin methylene disalicylate (BMD), a commonly used in-feed antibiotic, through Illumina sequencing of the internal transcribed spacer 2 (ITS2) region of fungal rRNA genes. Out of 124 samples sequenced, we identified a total of 468 unique fungal features that belong to four phyla and 125 genera in the GI tract. Ascomycota and Basidiomycota represented 90% to 99% of the intestinal mycobiota, with three genera, i.e., Microascus, Trichosporon, and Aspergillus, accounting for over 80% of the total fungal population in most GI segments. Furthermore, these fungal genera were dominated by Scopulariopsis brevicaulis (Scopulariopsis is the anamorph form of Microascus), Trichosporon asahii, and two Aspergillus species. We also revealed that the mycobiota are more diverse in the upper than lower GI tract. The cecal mycobiota transitioned from being S. brevicaulis dominant on day 14 to T. asahii dominant on day 28. Furthermore, 2-week feeding of 55 mg/kg BMD tended to reduce the cecal mycobiota α-diversity. Taken together, we provided a comprehensive biogeographic view and succession pattern of the chicken intestinal mycobiota and its influence by BMD. A better understanding of intestinal mycobiota may lead to the development of novel strategies to improve animal health and productivity.