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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

🔚 Together, these findings pave the way for exploring the microbiota of extinct species and offer deeper insights into the dynamics of their microbial ecosystems, contributing to a broader understanding of the biology of species that are no longer with us. #Mammoths #aDNA #Paleomicrobiology #Cell

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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

⑦ An 𝘌𝘳𝘺𝘴𝘪𝘱𝘦𝘭𝘰𝘵𝘩𝘳𝘪𝘹 species was recovered from a tooth of a Steppe mammoth that lived 1.1 million years ago in Adycha, Russia. This finding provides a unique opportunity to study how bacterial DNA can be preserved over such vast timescales, dating all the way back to the Early Pleistocene.

Mammuthus trogontherii. (Creator:Dmitry Bogdanov)

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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

⑥ A bacterium linked to an African elephant pathogen 𝘗𝘢𝘴𝘵𝘦𝘶𝘳𝘦𝘭𝘭𝘢 → closely related to the strain behind fatal septicemia in Zimbabwe elephants (2020). It may have caused similar disease in mammoths, even if this cannot be established with certainty.

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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

⑤ 𝐂𝐨𝐦𝐦𝐞𝐧𝐬𝐚𝐥 𝐛𝐚𝐜𝐭𝐞𝐫𝐢𝐚 𝐢𝐬𝐨𝐥𝐚𝐭𝐞𝐝 𝐟𝐫𝐨𝐦 🦷 • 𝘚𝘵𝘳𝘦𝘱𝘵𝘰𝘤𝘰𝘤𝘤𝘶𝘴 → oral microbe related to modern strains causing cavities in many other animals 🪥 • 𝘈𝘤𝘵𝘪𝘯𝘰𝘣𝘢𝘤𝘪𝘭𝘭𝘶𝘴 → probably from an oral bacteria found in 9 woolly mammoths, showing lineage continuity from the Late Pleistocene to Wrangel Island extinction ⌛

Mammoth tooth (photo by Peter Mortensen)

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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

③ 𝐇𝐨𝐰 𝐰𝐞 𝐝𝐢𝐝 𝐢𝐭? • Compared sequences with soil and lab contaminants • Checked for signs of ancient DNA degradation • Used phylogeny to trace evolutionary relationships compared to other animal bacteria. This let us focus on microbes truly associated with living mammoths. What did we found ? ⬇️

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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

① 𝐖𝐡𝐚𝐭 𝐰𝐞 𝐝𝐢𝐝? We analyzed 483 mammoth specimens from North America and Britain to Siberia, and date from the Early Pleistocene — around one million years ago — to the extinction of the last mammoths on Wrangel Island (a remote island off the coast of Siberia) during the Holocene, 4,000 years ago.

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Benjamin Guinet @benjaminguinet.bsky.social · 03/09/2025

🧵 Exciting news from our lab #CpgSthlm! 🥳 Thousands of years ago, mammoths roamed, and so did their fascinating microbial companions. Our latest study, published in 𝘊𝘦𝘭𝘭, brings them to light 🦣🦠🧬 Read the full paper here 👉 doi.org/10.1016/j.ce...

Mammoth tusk emerging from the permafrost on Wrangel Island (Siberia) in 2017 (photo by Love Dalén)

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Benjamin Guinet @benjaminguinet.bsky.social · 21/08/2025

Please share this Global South survey 🙏 #ESEB2025

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Benjamin Guinet @benjaminguinet.bsky.social · 28/07/2025

7) Yes, I said domesticated! After viral DNA accidentally integrates into the host genome, it can sometimes be co-opted to boost the host’s survival. In wasps, this means using viral genes to produce virus-like particles injected with the egg, helping suppress the host insect’s immune system.

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Benjamin Guinet @benjaminguinet.bsky.social · 28/07/2025

6) This virus–wasp relationship isn’t new, it’s been going on for millions of years. Over such long timescales viral DNA can accidentally integrate the wasp’s genome. This is not rare, take mammals for instance, part of the placenta is the result of a retrovirus domesticated gene (𝘴𝘺𝘯𝘤𝘪𝘵𝘪𝘯).

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Benjamin Guinet @benjaminguinet.bsky.social · 28/07/2025

4) To understand this, let’s zoom in on the wasp’s lifestyle. For the unlucky host insect, getting injected with wasp eggs is a death sentence, unless its immune system fights back. Over time, insects have evolved smart defenses, like encapsulating the eggs to block and kill them before they hatch.

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Benjamin Guinet @benjaminguinet.bsky.social · 28/07/2025

3) However, this comes at a cost to the wasp: her egg now has to compete with others inside the same host. This is a situation they usually avoid by carefully probing their prey first. Nevertheless, these spaghetti-shaped viruses (see TEM image) also confer some mutual benefits on the wasp.

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Benjamin Guinet @benjaminguinet.bsky.social · 28/07/2025

2) These DNA viruses have co-evolved with parasitoid wasps for millions of years, and they’ve learned a clever trick. They manipulate the behavior of infected female wasps to lay their eggs in hosts that are already infected with egg, increasing the chances for the virus to spread in the population.

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Benjamin Guinet @benjaminguinet.bsky.social · 28/07/2025

1) Parasitoid wasps live a brutal life: they lay eggs inside other insects, and the larvae eat their hosts from the inside out. Think Alien, but real, and with bugs.

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Benjamin Guinet @benjaminguinet.bsky.social · 21/07/2025

4) In contrast, damage intensity is driven by how genetically distant the reference genome is from the reads. This makes comparing damage curves between hosts and past symbionts or other microbes much trickier and needs to be taken into account by looking at the reference genome divergence distance.

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Benjamin Guinet @benjaminguinet.bsky.social · 21/07/2025

3) This is partly because fewer reads map to distant references, but we show that this mostly affects the stochasticity (variability) of damage patterns.

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Benjamin Guinet @benjaminguinet.bsky.social · 21/07/2025

2) In that context, when mapping aDNA reads to distant available reference genomes, we show that sequence divergence may obscure such C-to-T damage signals.

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