New molecule explains earthworm digestion mystery

A newly identified molecule in the gut of earthworms allows them to digest plant material a new study suggests.

An international team of researchers led by the Imperial College London used molecular microscopes and identified molecules – named drilodefensins – in the gut of earthworms that counteract the plant's natural defences and enable digestion.

Dr Manuel Liebeke at the Max Planck Institute for Marine Microbiology, in Germany, said: “Using these molecular microscopes is changing how we understand complex biochemistry of living beings; we are now able to locate every molecule in, for example, an earthworm to a specific location. Knowing the location of a molecule can help us to figure out what it actually does.”

In the study, published in the journal Nature Communications, the team observed the counteraction between drilodefensin molecules and polyphenols – micronutrients that act as antioxidants and give plants their colour – in the digestive system of earthworms. They discovered this counteraction allows earthworms digest fallen leaves and other plant material.

The scientists estimated that for every person on earth there is at least 1kg of drilodefensins present within earthworms. Despite their abundance, they suggest that these molecules are so precious that earthworms recycle them in order to harness their properties again.

“We’ve established that earthworms, referred to as ‘nature’s ploughs’ by Charles Darwin, have a metabolic coping mechanism to deal with a range of leaf litter diets. In this role, drilodefensin support the role of earthworm as key "ecosystem engineers" within the carbon cycle,” said research associate Dr Dave Spurgeon.

The team also found a relationship between the micronutrient and the molecule where the more polyphenols present in the earthworm diet, the more drilodefensins they produce in their guts.

Paper: http://www.nature.com/ncomms/2015/150804/ncomms8869/full/ncomms8869.html