The common vampire bat has adapted to a diet that is low in nutrients and exposes the animal to a broad range of blood-borne diseases, reveals a joint study of its genome and gut microbiome published online this week in Nature Ecology & Evolution. Compared with nectar-feeding, fruit-eating, and meat-eating bats, the microbiome in vampire bats is completely distinct.

The common vampire bat (Desmodus rotundus) is one of only three mammal species that feed exclusively on blood. Unlike other feeding strategies, consuming blood is an extreme evolutionary specialisation, as blood is a nutrient-poor resource that is low in carbohydrates and vitamins, and which may harbour blood-borne diseases.

Marie Zepeda Mendoza and colleagues investigate how this dietary specialisation has impacted both the host and the gut microbiome by jointly sequencing the bat's genome and faecal metagenome (the microbial DNA sample recovered from the bat’s droppings). They find that although the genome’s overall size is similar to those in other species of bat, it contains around twice the copy number of transposable elements (DNA sequences that change position in the genome). These sequences were found in genomic regions related to immune response, viral defence, and both lipid and vitamin metabolism.

Using the faecal metagenome as a proxy for the gut microbiome, they also identify microbial taxa and functions not found in other species of non-blood-feeding bats, including more than 280 bacterial species known to cause disease in other mammals. The authors argue that analysing both the genome and gut microbiome provides a framework for studying extreme dietary adaptations that influence host species on a whole-organism level.