How Earthworms, Bacteria, and Time Dance Together

Earthworms have tiny buddies living in their excretory organs. Two of these are Verminephrobacter and Flexibacter-like bacteria. Almost all lumbricid earthworms host Verminephrobacter, which are passed from parent to offspring. These bacteria have been with their earthworm friends for a very long time, maybe since their ancestors lived together around 100 million years ago! Flexibacter-like bacteria, on the other hand, are found in about half of the studied earthworms and can switch to new hosts. They might have started their relationship with earthworms around 45 million years ago. Scientists looked at the DNA of 18 earthworm species and their bacterial friends to understand this unique partnership. They found that Verminephrobacter and earthworms have evolved together for a long time, while Flexibacter-like bacteria can adapt to new hosts. The Flexibacter-like bacteria are so unique that scientists think they should be in their own genus, which they named Candidatus Nephrothrix. Isn't that fascinating?