Meeting Abstract
Recently, there has been a great deal of attention focused on the role that symbiotic bacteria play in the development, ecology, and evolution of hosts. Avian altricial nestlings represent an interesting study system in which to investigate these interactions, given that they exhibit the fastest growth rates among vertebrates, and growth is limited by their digestive capacity. We used 16S rRNA sequencing to inventory microbial communities in several experiments testing various questions. 1) How do microbial communities develop in the wild? 2) How responsive are gut microbes to dietary changes? 3) Does hosting microbes incur a cost to developing nestlings? When sampling nestlings from the wild, we found that aspects of bacterial community membership and structure changed significantly over the nestling period. The relative abundance of Proteobacteria decreased around day 9, while the relative abundance of Firmicutes increased. When we conducted feeding trials in captivity, we found that the microbial communities were altered within 6 hours of a diet shift. Last, we treated some nestlings with antibiotics. Antibiotic treatment significantly increased growth and food conversion efficiency in nestlings. Antibiotics did not alter aspects of gut anatomy, but depressed intestinal maltase activity. Thus, we conclude that microbial-induced growth limitation in developing birds is not driven by interactions with digestive capacity, but may be driven by decreased energetic costs of immune function or beneficial effects from microbes enriched under antibiotic treatment. Overall, these studies demonstrate that the digestive system and gut microbiota of developing House Sparrows respond rapidly to changes in diet.
