Another Life: The strange world of slime mould, ‘dog vomit’ and Ebola

The first storm of autumn left the polytunnel plastered with leaves from its sheltering spinney, a kaleidoscope of soft ochres and greens in stained-plastic shapes against the sky. I was gazing up in pleasure when the world ended with a blinding flash and a bang like a stun grenade. Across the bay at Renvyle, this or an allied stroke set a house on fire and cost a couple their home.

The shock jolted me back to last winter when lightning leaped from a light switch, crippled the telly and silenced our house phone for a month.

If this is climate change – and it feels much like it – Met Éireann might care to change its language. Lightning storms, not thunder, could come to warrant orange warnings of their own.

From the cosmic to the microscopic. In the month of moulds and mildews, rots and fungi, it has been a race to harvest the tunnel’s tomatoes in good health and bring the last and greenest to ripen indoors. The lightning caught me dismantling their empty vines and chopping them gently, with secateurs, into carefully portable lengths without disturbing their wounds.

Occasional, inescapable little grey puffs, as of smoke or dust, reminded me that Botrytis cinerea can produce 60,000 or more spores from a fragment of rotting tissue no bigger than your fingernail. Even scientists call this fungus aggressive, as, nourished on the sap leaking from a broken leaf or withering flower, a single spore invades the plant to feed within its stems.

Fungi live some strange lives. Again this autumn, Eye on Nature has received photographs of the slime mould Fuligo septica, scattered on grass or fallen leaves in separate blobs like scrambled egg, as in my drawing, or frothily combined in masses that remind some people – Americans mainly – of "dog vomit".

Neither actually fungus nor animal, but sharing the ancestry of both, the Myxomycetes, as the group is called, start out as microscopic single cells with one nucleus, hatching from spores blown on the wind or excreted by insects.

The cells swim through moisture with whip-like flagellae, then grow into free-living amoebas that eventually meet up and fuse into blobs or even a big pancake mass, containing millions of nuclei, called a plasmodium.

This is still a single cell, but it can move about, “crawling” perhaps 10cm a day in search of bacterial food – even, indeed, climbing a tree to attack a bracket fungus. This shape-shifting togetherness has slime-mould specialists writing of “altruism” and “social behaviour”.

The moulds also get credit as significant decomposers, nutrient recyclers and controllers of bacterial populations, thus answering the forbidden question of what things in nature are “for”.

As one moves down the microscopic scale to the more primitive structures of bacteria and – even smaller – viruses, their interaction with Earth’s biochemistry becomes mesmerising in its scale and intricacy.

Living beside the Atlantic, I am especially fascinated to learn that a single drop of coastal surface seawater is likely to hold about 500,000 viruses. (A litre collected near Galápagos contained at least 100 billion.) As the ocean's most abundant life forms, their impact on microbial life is profound and now closely studied. They infect and kill the almost equally abundant ocean bacteria, releasing their carbon and other elements for use elsewhere in the micro-organism food chain.

The viruses on land bring Earth’s total to more than 1,000 species, with many more awaiting discovery.

As mere little packets of genes – a central core of DNA or RNA wrapped in a coat of protein – they are the prime agents of the destruction we call disease. They act to survive by invading the cells of their hosts and using their DNA machinery to replicate themselves.

No one has written more plainly of viruses than the evolutionary biologist and atheist crusader Richard Dawkins. "Like a computer virus," he wrote in Climbing Mount Improbable, in 1996, "the biological virus simply says 'copy me and spread me around'." At that time the virus heading the news was the one producing Aids. Today it is Ebola, similarly a transfer to humans from African bushmeat.

Like every other species in nature, as Dawkins says, viruses have no special interest in killing people: the sickness and death that attend their multiplication are purely incidental.

The delay in producing disabling symptoms makes time for exponential infection, and the explosive later symptoms of Ebola seem almost as deliberate a means. Some minds, indeed, might suspect a planetary device for controlling the grossly excessive human population.

Dawkins, loyal to Darwin, has no more need of Gaia than of God. Viruses, he wrote, are “here because they’re here because they’re here. If they didn’t embody instructions to ensure that they exist, they would not exist.”

Ours, after all, is not to reason why.