The Colonic Microbiome as a Complex, Food Safety-related Trait in Beef Cattle

The vertebrate gut is home to hundreds to thousands of species of microbial symbionts that play roles in development and physiology of the host.  Across individuals, gut microbiota composition is relatively conserved at its highest taxonomic levels, but varies tremendously in the microbial species present and in their relative abundances.  Recent work from our group in the mouse model has established that quantitative variation in species composition arises from a complex combination of environmental factors and host polygenes.  These Quantitative Trait Locus (QTL) mapping studies have now identified 45 different QTLs that control microbiota composition in the mouse.  Microbial taxa that are influenced by these QTLs span much of the microbiota phylogenetic space with several QTLs having pleiotropic effects.  Like the mouse, the bovine colonic microbiota also comprises a wide variety of microbial taxa, including zoonotic pathogens such as Enterohemorrhagic E. coli (EHEC), and Salmonella.   We have hypothesized that the bovine microbiota, including EHEC and Salmonella, also behave as complex polygenic traits and could therefore be targeted as “food safety” traits in breeding programs.  We are currently testing this hypothesis by QTL analysis of the microbiota across mapping populations bred to represent the 16 most common breeds of beef cattle.  Preliminary phenotyping of the microbiota from mapping populations have identified a core set of >60 taxa that are log-normally distributed across several cohorts.  Analyses are currently underway to examine relationships between correlated groups of taxa within the core and colonization by EHEC and Salmonella.