There are a lot of things that humans believe that they have invented or discovered that just isn’t true at all. When our ancestors were first contemplating the domestication of cattle or goats as a source of meat and milk, some ants had already been raising aphids (corralling them, nurturing them and living off their “milk”) for millennia. Now, in a paper from the Proceedings of the Royal Society, Thomas Chouvenc has discovered that even our systematic use of antibiotics isn’t actually all that novel.
Formosan subterranean termites (Coptotermes formosanus) are one of the most destructive species of termites in the world. Originating from China and then hopping over to Taiwan, where they received their name, they have now been inadvertently introduced into Japan, Hawaii, South Africa and the United States. A mature colony can contain several million termites and can consume nearly a pound of wood every day, foraging an area of over 70,000 square meters! At that rate, they can practically destroy a house in a matter of months and no established colony of Formosan termites has ever been successfully eradicated.
The Formosan termites build a sponge-like structure within the galleries of their colony which is a composite mix of wood particles and faecal material, usually called “carton material”. The carton is instrumental in stabilizing the colony structure as well as helping maintain temperature and moisture level within the colony. But with relatively high temperatures and moisture, there is also a higher probability of fungal or bacterial infections in the colony as well. Metarhizium anisopliae is just such a fungal pathogen. M. anisopliae is a naturally occurring parasitoid that lives in soils throughout the world. It is known to infect over 200 species of insects, including termites, and has been used as a biological insecticide against a number of such pests. However, to date, Formosan termites have remained relatively immune to such challenges and Chouvenc now understands why.
Chouvenc’s group found about 500 Actinobacteria isolates from 5 different Formosan colonies and over 70% of those isolates showed in vitro antimicrobial activity against a range of gram negative and gram positive bacteria, yeast, and fungi. The most common isolate was Streptomyces, the source of many of our most popular antibiotics, including Streptomycin, Chloramphenicol, Puromycin and Tetracycline. These naturally occurring bacteria, with their antibacterial components, effectively provide resistance to the termites for many of the pathogens they encounter inside their colonies. Chouvenc found that the termite’s faecal lining of the carton material in the foraging galleries acted as a perfect niche for the colonization of microorganisms like Actinobacteria and that colonies which had access to Streptomyces when infected with M. anisopliae had a significantly higher survivability than colonies which lacked Streptomyces.
One limitations of Chouvenc’s research was that all five colonies were derived from Florida, where Formosan termites are an invasive species. So there’s more research to be done to discover if this was a localized recruitment event post invasion or if this was an inherited trait of the native species.
The most fascinates part of this discovery for me is the way in which these termite colonies thrive in the presence of their natural antibiotics. Imagine if we were to coat not only our clothes, but our houses, linens, beds, chairs, tables etc. with a profusion of antibiotics all the time. Experience has shown us that we would be (and are!) inundated with larger numbers of resistant varieties of our pathogens from such overuse. In fact, the CDC just posted a news bulletin highlighting this issue exactly.
But here we have termites who are seemingly able to bypass that natural tendency and survive! This is a bigger question than simply, “How can we use this knowledge to eradicate this pest”. Instead, we should be asking: How can we learn from these creatures to use our antibiotics more prudently and effectively? How can we continue to use the same antibiotics over a long period of time, overcoming the threat of resistance and antibiotic failure? These bugs seem to have been doing this, effectively, for millions of years…there is still so much for us to learn.
Chouvenc, T., Efstathion, C. A., Elliott, M. L., and Su, Nan-Yao (2013). Extended disease resistance emerging from the faecal nest of a subterranean termite. Proceedings of the Royal Society B, 280: 20131885.
Category Code: 79102 79101 88221
