Microbiology: The vulture’s iron gut

The first analysis of the gut microbiome of the vulture is reported online this week in Nature Communications. The study found that Clostridia and Fusobacteria, bacteria that are widely pathogenic to other vertebrates, dominate the vulture’s gut microbiota, likely due to adaptations to a diet of decaying flesh.

Microorganisms present in vertebrates rapidly begin to decompose their hosts after death. As they break down tissue, these microorganisms excrete toxins that render the carcass a hazardous food source for most animals. Despite increasing the risk of exposure to toxins, this initial decomposition may be necessary to allow vultures to scavenge carcasses with tough skins. In addition, to obtain access to the inside of such carcasses, vultures often insert their heads directly in the body cavities of decaying prey, exposing their head and neck to pathogenic bacteria.

To determine how vultures are able to tolerate these toxins, Michael Roggenbuck, Lars Hansen, Gary Graves and colleagues characterise the microbiome of the facial skin and the hindgut (large intestine) of the two most widespread species of vultures in the New World: the black vulture (Coragyps atratus) and the turkey vulture (Cathartes aura). They find that the DNA of prey species, detected on facial swabs, was completely broken down in the gut samples from most vultures, indicating the presence of extraordinarily harsh chemical conditions in the vulture gastrointestinal (GI) tract. They also show that the acidic GI tract of vultures is a strong filter for microorganisms ingested from decaying carcasses, resulting in hindgut flora dominated by Clostridia and Fusobacteria. These microorganisms appear to have adapted to survive the harsh conditions and may also confer benefit to the vultures by further breaking down carrion, possibly exemplifying a specialized host-microbial alliance.