If you think that outsourcing is a 20th or 21st century phenomenon, think again. It’s been going on for eons in nature. For evidence, look no further than a lowly marine worm.
Spotted and isolated for the first time about five years ago off the coast of Elba, the Mediterranean island to which Napolean was exiled to, Olavius algervensis, a worm belonging to a species of marine oligachaete, surprised researchers. The worm does not have a mouth to ingest food or an anus to throw away its metabolic waste.
The scientists found that the worm does not have a gut or kidneys. As part of its unique lifestyle, O. algervensis enlists the services of symbiotic microbes for energy production and waste management. The worm carries bacterial tenants, harboured under its skin, and lives in rich coastal sediments where the latter can find sources of chemical energy. In return, the bacteria synthesise all the required amino acids and vitamins to fulfill the nutritional requirements of their host. At the other end of the digestive system, waste products such as ammonia and urea generated by the worm’s metabolism are taken up by these microbes, thus not only relieving the worm of toxic waste products but also conserving valuable nitrogen, an element essential for life for the microbial community.
Scientists from the Joint Genome Institute in the US and the Max Plank Institute of Marine Microbiology in Germany recently mapped the genome of the worm. Their findings, reported in the September 17 issue of the journal Nature, resolved many mysteries associated with the worm, which is several times thinner than its other family members. An adult O. algervensis worm grows to a maximum length of two centimetres.
“It is an excellent example of outsourcing energy and waste management, where this worm and the microbes living under its skin enjoy a mutually beneficial relationship,” JGI director Eddy Rubin said in a statement issued by the institute. “The microbes, floating around in the sea, strike up a bargain with the worm; in exchange for housing, the microbes take care of energy production and handling the waste.”
What is stunning about the worm-microbe quid pro quo is that it involves several different microbial communities. Generally, in most symbiotic relationships between larger organisms and microbes, only one microbial species is present.
It turns out that the worm not just houses the microbes but also works as a vehicle for microbes. The worm burrows into the sediment and as it heads for different environments, each with different chemical constituents, provides energy adapted to the capabilities of a particular group of microbes. As the worm does not have a mouth, the microbes use chemical energy from the sediment, which goes through the skin, to convert organic material into the stuff that nourishes the worm.
At times, the microbes feed on even substances considered toxic for their host but convert them into harmless products which can safely be metabolised by the worm.
For instance, sulphide is considered toxic for most animals. The symbiotic sulphur bacteria of the gutless worm take up sulphide and convert it to non-toxic byproducts which can be fed subcutaneously to the worm.
The researchers liken this to the functioning of a hybrid car that can run on both electricity and petrol, depending on the situation. In certain places, the worm is powered by special bacteria that can exploit the chemical energy abundant in a specific location, while in other strata, where a different chemical energy source is abundant, the worm switches its energy production to resident bacteria that can exploit that available energy source.