When it comes to interactions between animals and microbes in the ancient past, focus has primarily been on humans and our closest ancestors rather than extinct animals, such as mammoths.
A new study led by Benjamin Guinet from the Swedish Museum of Natural History has analysed microbial DNA from no fewer than 483 mammoth remains. These remains span over one million years and were uncovered from seven sites located in Canada and Russia.
Using a variety of different genetic techniques, Guinet and his team identified 310 microbes from a range of different mammoth tissues, from teeth to tibia.
While most of these microbes are thought to have been derived from the surrounding environment after death, there are six that have been identified as ‘host-associated’, meaning they lived symbiotically inside (or on) their hosts.
The dataset assembled by Guinet and his team includes 440 newly sequenced and unpublished samples from a 1.1-million-year-old steppe mammoth found near the Adycha River in northeastern Russia, deep in the wilderness of Siberia. In 2021, scientists successfully recovered DNA from a molar of this particular mammoth. This proved to be the oldest DNA ever sequenced from animal remains, making the so-called ‘Adycha Mammoth’ particularly famous.
From this same molar and as part of this latest study, Guinet and his team recovered genomic evidence of a host-associated microbe known as Erysipelothrix, which, again, was the oldest of its kind ever found.
Erysipelothrix is a type of bacteria that has previously been isolated from dogs, pigs, cattle and humans and is thought to be involved in endocarditis – a potentially fatal infection of the inner lining of the heart.
Evidence of Erysipelothrix-like bacteria was also discovered in woolly mammoth bones from a different time period and site. The presence of Erysipelothrix in both species of mammoths suggests this bacteria has a long-term association with the group and may have had some influence on mammoth evolution.
The study found genomic evidence of five more types of host-associated bacteria, including Pasteurella and Streptococcus.
Some of the Pasteurella DNA isolated from two Late Pleistocene mammoth samples was very similar to a strain of bacteria identified as causing fatal septicaemia in six African elephants in Zimbabwe in 2020.
And of two distinct types of Streptococcus identified from six woolly mammoth teeth, one was found to be distantly related to a strain of Streptococcus responsible for tooth decay in humans.
Despite its somewhat bad reputation, bacteria isn’t inherently ‘harmful’. In fact, many of the types identified in this study, including Erysipelothrix, Pasteurella and Streptococcus, can be harmless or even beneficial and only cause disease under certain conditions.
Pasteurella, for example, is involved in the production of succinic acid – a naturally occurring acid that plays a crucial role in metabolism and energy production.
Not only has this latest study assembled a giant database that will form the basis of further studies into the microbiomes of mammoths, it has also shown that it’s possible to detect host-associated bacteria in the remains of extinct animals.
This new area of research has the potential to change what we thought we knew about the long-term health of extinct animals and how their microbiomes may have shaped their evolutionary trajectories.
Top image: mammoth tusk. Credit: Love Dalén
More amazing wildlife stories from around the world