The types of gut bacteria that populate the guts of primates depend on the species of the host as well as where the host lives and what they eat. A new study examines the gut microbial communities in great apes, showing that a host’s species, rather than their diet, has the greatest effect on gut bacteria diversity.
Bacteria are crucial to human health. They enhance the immune system, protect against toxins, and assist in the maturation and renewal of intestinal cells. Gut microbes outnumber our own cells by 10 to 1 but little is known about how certain species come to populate our stomachs, which are sterile at birth. What causes this variation within microbial communities has been a matter of debate. Some scientists have argued that diet and habitat play the most prominent roles. The new research finds that diversity in the composition of these gut communities, not including those occasional transients and unwelcome visitors such as pathogenic bacteria, depends primarily upon the host species.
Using genetic markers, the researchers measured the diversity and abundance of various microbial species found in fecal matter of five great ape species collected in their native ranges and discovered that bacterial populations assorted to species. Moreover, the relationships of the microbial communities matched that of their host. In other words, not only is it possible to differentiate chimpanzees from humans by examining the microbial populations within their guts, but these gut microbes have been tracking the evolution of their hosts for millions of years.
Evolutionary Relationships of Wild Hominids Recapitulated by Gut Microbial Communities. (2010) PLoS Biol 8(11): e1000546. doi:10.1371/journal.pbio.1000546
Multiple factors over the lifetime of an individual, including diet, geography, and physiologic state, will influence the microbial communities within the primate gut. To determine the source of variation in the composition of the microbiota within and among species, we investigated the distal gut microbial communities harbored by great apes, as present in fecal samples recovered within their native ranges. We found that the branching order of host-species phylogenies based on the composition of these microbial communities is completely congruent with the known relationships of the hosts. Although the gut is initially and continuously seeded by bacteria that are acquired from external sources, we establish that over evolutionary timescales, the composition of the gut microbiota among great ape species is phylogenetically conserved and has diverged in a manner consistent with vertical inheritance.