How Gut Microbes Allowed Termites To Conquer The World

Termite workers eating wood with a soldier in the middle. Jan Sobotnik

Termites have become among the most successful clades of animals, yet they could not have done it without their gut bacteria. A study of this microbiota has revealed something extraordinarily complex and finely tuned, as well as the role of cannibalism in the termites' success.

Breaking down the lignocellulose of wood is hard, and few animals have evolved to do it. The bacteria in a termite's gut convert their food to sugars, which then become the termite's energy source. Working out how this is done could be the key to better biofuels. We could look at termites as nothing more than vehicles that move their bacteria around to access more wood. Indeed, gut bacteria make up an astonishing two-thirds of termites weight. However, this misses the other achievement of termites: getting diverse bacteria to cooperate with exceptional efficiency.

“There can be up to 5,000 different species of microbe ‘machines’ in a termite gut, and many thousand clones of each kind,” Professor Nathan Lo of Sydney University said in a statement. Humans have about 1,000 species, and as Lo noted to IFLScience, the human gut is a lot larger, making the ratio by volume look a lot more impressive.

Although the importance of termite gut bacteria has been known for a century, Lo told IFLScience there's been debate about these microbes' transmission. One theory held they were passed on from generation to generation within the nest, while the other proposed termites picked them up from their environment.

In Current Biology, Lo has demonstrated that while much transmission takes place within the nest, transfer also occurs between termite species. Lo told IFLScience: “When comparing the gut bacteria we studied with everything else on the databases, termite bacteria was always more similar to species from other termites than to anything else.” He concluded that termites rarely collect new bacterial species from the soil, and quickly adapt what they adopt to fit their needs.

From there, bacteria have a gruesome way of getting to other termite species. “In fights between soldiers of one colony with soldiers or workers of another colony, the body of the losing termite can be severed and its gut contents (containing the microbes) ingested by the winning termite,” Lo said.

Having evolved from rotten wood-eating cockroaches, termites spent the first hundred million years of their existence sticking to what they knew. However, Lo told IFLScience diversification began 40-50 million years ago, with some species eating leaf litter while others went the whole way to consuming soil.

The extent of termite success can be measured by estimates that their collective weight is greater than any other related group of animals besides cattle. Estimates are of course uncertain, but Lo told IFLScience available figures suggest termites collectively weigh more than all the world's krill, whales, or humans.

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