Over three hundred years ago, in a letter to Hendrik van Bleyswijk dated 9th February 1702, the pioneering microscopist Antony van Leeuwenhoek (right) described a remarkable phenomenon. He discovered that when dry and apparently lifeless dust from a roof gutter was rehydrated with clean water, many small “animalcules” became active within an hour, variously “adhering to the glass, some creeping along it, and some swimming about.” This result, observed with his characteristic single lens microscopes, was routinely reproducible, even with dust kept dry for many months. Leeuwenhoek was astonished: “I confess I never thought that there could be any living creature in a substance so dried as this was”. His astonishment is understandable, since we know that without water, there can be no life, and yet Leeuwenhoek is describing creatures which apparently survive desiccation.
Anhydrobiosis (from the Greek for “life without water”) is the state of suspended animation which certain organisms enter in response to desiccation; such organisms are found across a range of taxa, including bacteria, yeasts, plants and many invertebrates such as nematodes and bdelloid rotifers. Survival of desiccation and the dry state is one of the most intriguing phenomena in nature, but is far from fully understood. It is believed that a number of components are important in protecting these organisms from desiccation damage including the highly hydrophilic LEA proteins and the build up of non-reducing disaccharides like trehalose.