Koalas are discriminating gourmets. Maybe a little too much, since many of them only tolerate leaves from white gum trees (Eucalyptus viminalis). That is why they are vulnerable to starvation in case of scarcity. Nonetheless, some of them can feed from other species of eucalyptus, especially messmate (Eucalyptus obliqua) which is more fibrous and less nutritious but very widespread. This difference led Australian researchers to study a potential link between the composition of marsupials gut microbiota and their ability to digest the components of the leaves from these two trees.
Link between microbiota and diet
The comparison between the gut microbiota of koalas who only eat white gum leaves or only messmate leaves confirms there is a difference in their gut microbiota composition: the latter present a higher content of species from the Lachnospiraceae and Ruminococcaceae families, which are bacteria known to promote the degradation of cellulose, more abundant in the intestines of messmate-eating koalas.
Unchanged microbiota
Koalas preferring white gum leaves and held in captivity were given alternately leaves of both eucalyptus species. The objective was to assess whether a change in diet would lead to a change in the composition of the gut microbiota. This phenomenon, frequent in any animal species and in humans, was not observed here. This is the proof that koalas have a low microbial adaptability to dietary changes, which can explain why they reject some leaves.
Towards a probiotic for the survival of the species?
However, the administration of fecal matter capsules from wild messmate-eating koalas to koalas eating exclusively leaves from white gum trees changed the gut microbiota of the recipients and allowed them to eat other species of eucalyptus. Eating habits then evolved over time: as the gut microbiota became more similar to that of donors, these marsupials tended to eat more messmate leaves. Therefore, a probiotic approach through fecal transplant could prove useful in helping koalas adjust to a new environment or to the increasing scarcity of their favorite leaves, thereby ensuring their survival.
