by Lisa Keilhofer

News from the animal world. Microbiome and nutrition.

Large scale sequencing of koala feces was performed and revealed the microbiomes of various koala populations. (Picture: © RyanFowlerPhotograph -

In our mission to keep you updated on all the latest findings in microbiome science, we would like to take a glance at what’s new in animal microbiome research. As our frequent readers know, animal research is an important prerequisite for understanding the human microbiome, as the parallels are numerous. But not all research on animals can be transferred to humans, and in some cases, quite the opposite seems to be the case. Here are two interesting findings we would like to introduce to you:

Koalas cannot digest any random eucalyptus

As early as August 2019, “Animal Microbiome” published results of a study by Michaela D. J. Blyton, Rochelle M. Soo and colleagues on koala feces. Large scale sequencing of koala feces was performed and revealed that the microbiomes of various koala populations showed a direct correlation to their feeding on specific eucalyptus species. For humans goes that nutrition directly influences the composition on the microbiome. Interestingly, for koalas, it seems to be just the other way around. The koala baby takes on the mother’s gut microbiome when getting into contact with her feces at birth. The setting of the gut microbiome, however, is a crucial factor for which eucalyptus species are digestible and which are not for the koala. And in the case of a shortage of the usual food supply, the individuum cannot just fall back on other eucalyptus species but is dependent on the one species for its entire koala life, because once colonized the microbiome cannot just be re-set as simple as that (under natural conditions). However, scientists were able to implant a koala the microbiome of a conspecific that was used to different eucalyptus nutrition and the surprising result was that now the koala was able to digest the “new” eucalyptus that he was not able to feed from until then.

This result is even more important as just now, hundreds of acres of eucalyptus forests were on fire and important sources of nutrition (and of course living space) were destroyed for thousands of koalas. The animals that were saved from the fires cannot just be re-settled in intact forests of other eucalyptus species. What could safe the homeless animals might be a – clearly more complex and expensive – fecal transplant of fellow koalas from their new homes-to-be.

Apart from that practical relevance, the outcome of the study has, of course, also scientific relevance: with koalas, the nutrition does not influence the microbiome, but the other way around – the microbiome sets the prerequisite of which nutrition is digestible for the animal and which is not.

Bird, bats and the microbiome.

Another study on animal’s microbiomes was published in December 2019 by the University of California, San Diego. Until today, the assumption was, that there is a strong correlation and interplay between microbiome and host and that similar species have comparable microbiomes. This new study now reveals the ability to fly to be a possible key factor for the composition of the microbiome. The study examined bats and birds and came to the conclusion that species able to fly aim at the lowest weight possible. The microbiome is a good thing to start with: our human microbiome adds up to a few extra kilos to our total body weight. One if not the evolutionary advantage might therefore be to go down on microbes with no or only limited use.

Moreover, the study shows that the above-mentioned correlation of host and microbiome is not as close as estimated, so far. On the contrary, the study proved the most important thing in common between bats (respectively birds) and their microbiomes is that the correlation is not as big as postulated until today. There are species with very stable microbiomes that stay the same over thousands of years, whereas others seem to develop rather dynamically. Flying species turned out to be part of the latter, they develop independently from their microbiomes. Also, the total correlation of nutrition and microbiome is a bit relativized now, as also the koala study showed.

The team around co-first author Se Jin Song, PhD is excited about the outcome that marks a paradigm shift in animal microbiome research. Also Dr. Rob Knight, renowned microbiome scientist, sees the study as starting point for further research with metagenomics and metabolomics. In other words, by these animal studies, we have taken an important step on our way to better understand our own human microbiome.

Lisa Keilhofer
Lisa Keilhofer

Lisa Keilhofer studied at the University of Regensburg. She works in internationalization and as a freelance editor.

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