How Soil Is Formed - Soil: Reflections on the Basis of our Existence - page 23

Supermuck. Bacteria in a biofilm form a gelatinous material that protects the colony from exter-
nal disruption. In human lungs, for example, antibiotics can have a hard time reaching the bacte-
ria in a biofilm, which can make some infections hard to combat. Observing the true nature of a
biofilm is difficult. In an electron microscope, the gelatinous material dries into a spaghetti-like
network. The image shows rod-shaped bacteria embedded in the material
Like these plants, Nostoc can photosynthesise and form carbohydrates from sunlight
and carbon dioxide. In South Africa and Australia, scientists have found biofilm traces
more than three million years old—the oldest known life forms on the planet.
Biofilms often form on underwater rocks. We have all trodden on submerged
rocks at the seaside and can doubtless imagine how fragments of biofilm might
dry out at low tide and be blown by the wind onto the shore. But some biofilm
organisms were able to survive on land. Many fungi have special pigmentation
to protect them against ultraviolet light, and their ability to withstand drought by
secreting a tissue-protecting barrier with high drought tolerance is likely to have
played a critical role in the formation of the first soil. Today we know that most
areas of land exposed to the atmosphere are covered in biofilms, some invisible to
the human eye and others forming delicate patterns on old stone buildings.
Inspiration from Crete
I took the opportunity to study fungi and their unique properties on a walking holi-
day one summer in Crete. The terrain on the southern side of the island is so rugged
that there are no coastal roads: getting there means walking or taking a boat. The trail
that runs west from the village of Sougia, south of Chania, passes a harbour and then
enters a leafy ravine where pink oleander bushes bloom and olive trees offer welcome
shade. Pigeons and tree sparrows nest in the steep sides of the gully—an environment