Wednesday, 26 September 2012

Moulds, mildew and mushrooms: living cheek by jowl with fungi

There is a form of life that probably exists in every house, office and workplace on the planet (operating theatres and clinical laboratories largely excepted) that is so ubiquitous that it goes chiefly unnoticed. The organisms are stationary yet spread rapidly, are composed of numerous species - some of which include common foodstuffs - and are neither animal nor plant. In other words they belong to the third great kingdom of macroscopic life: fungi. But what are these poor relations of the other two groups, seen as both friend and foe?

Having moved last year from a one hundred and thirty year old, centrally-heated and double-glazed terrace house in the UK to a single-glazed, largely unheated detached house less than a quarter that age in New Zealand, I've been able to conduct a comparative domestic mycology experiment. Without sounding  too much like a mould-and-spores collector out of a P.G. Wodehouse story, the subject has proved interesting and reasonably conclusive: a family of four moving to an annual climate on average four degrees warmer but with twice the rainfall has not substantially changed the amount or placement of mould in the home; if anything, it has slightly decreased. But then the amount of bathing, laundry and pans on the hob hasn't changed, so perhaps it's not too surprising. The more humid climate has been tempered by having more windows and doors to open, not to mention being able to dry more of the laundry outside. Mind you, one big plus of the move has been not having to use electric dehumidifiers or salt crystal moisture traps, so a few degrees warmth seems to be making a difference after all.

There appears to be a wide range of dubious stories, old wives' tales and assorted urban myths regarding fungi, no doubt being due to the lack of knowledge: after all, if you ask most people about the kingdom they will probably think of edible mushrooms followed by poisonous toadstools. Yet of the postulated 1.5 million species of fungi, only about 70,000 have so far been described. They are fundamentally closer to animals than they are to plants, but as they live off dead organic matter (and some inorganic substances too), thriving in darkness as unlike plants they do not photosynthesise, their reputation is more than a little sinister. The fact they will grow on just about any damp surface, hence the kitchen and bathroom mould populations, reinforces the opinion of them as being unwelcome visitors. So just how bad are they?

Firstly, fungi play a vital role in the nitrogen cycle, supplying nutrients to the roots of vegetation. The familiar fruiting bodies are, as Richard Dawkins describes them, pretty much the tip of iceberg compared to the enormous network of fungal material under the soil. Even so, they are given short shrift in popular natural history and science books: for example, they only warrant five pages in Richard Fortey's Life: An Unauthorised Biography, whilst Bill Bryson's A Short History of Nearly Everything spends much of its four pages on the subject concerned with the lack of knowledge about the number of species. Of my five Stephen Jay Gould volumes totalling over two thousand pages, there are just several, short paragraphs. And at least one of my books even refers to fungi as a simple form of plant life! Yet we rely on fungi for so many of our staple foodstuffs; it's just that they are so well hidden we don't consider them if they're not labelled as mushrooms.  But if you eat leavened bread, yoghurt, cheese or soy sauce, or drink beer or wine, fungi such as yeast will have been involved somewhere along the line. On another tack, fungi are party to yet another knife in the coffin of human uniqueness, since both ants and termites cultivate fungi: so much for Man the Farmer.

As this point I could start listing their uses in health cures, from traditional Chinese medicine to Penicillin, but my intention has been to look at fungi in the home. Anyone who has seen the fantastic BBC television series Planet Earth might recall the parasitical attack of the genus Cordyceps upon insects, but our much larger species is far from immune to attack. Minor ailments include Athlete's Foot and Ringworm whilst more serious conditions such as Candidemia, arising from the common Candida yeast, can be life- threatening . The spores are so small that there is no way to prevent them entering buildings, with commonly found species including Cladosporium, Aspergillus, and our old friend Penicillium.

Once they have a presence, moulds and mildew are almost impossible to eradicate. They are extremely resilient, with the poison in Amanita species such as the death cap failing to be destroyed by heat. An increasingly well-known example is the toxin of the cereal-infecting ergot, capable of surviving the bread-making process, even the baking. Indeed, ergot has seemingly become a major star of the fungi world, being used in pharmaceuticals at the same time as being nominated the culprit behind many an historic riddle, from the Salem witch trials to the abandonment of the Marie Celeste. Again, lack of knowledge of much of the fungal world means just about anything can be claimed with only dubious evidence to support it.

Varieties of domestic mould
A rogue's gallery of household fungi

Although we are vulnerable to many forms of fungus, an at least equally wide range attack our buildings. Whether the material is plaster, timber or fabrics, moulds and mildew can rapidly spread across most surfaces containing even a hint of dampness, often smelt before they are seen. At the very least, occupants of a heavily infested property can suffer allergies, sinus problems and breathing problems. As an asthmatic I should perhaps be more concerned, but other than keeping windows and doors open as much as possible there doesn't seem much that can be done to counter these diminutive foes.  As it is, vinegar is a favourite weapon, particularly on shower curtains and the children's plastic bath toys. Even so, constant vigilance is the watchword, as can be seen by the assorted examples from around the house above. For any mycophobes wondering how large fungi can get indoors, I once worked on a feature film shot in a dilapidated Edwardian hotel in central London about to be demolished which had fungal growths on the top floor (saturated with damp thanks to holes in the roof) which were the size of dinner plates.

So whether you've played with puffballs or like to dine on truffles, remember there's no escape: fungi are a fundamental element of our homes, our diet, and if we're unlucky, us too. Seemingly humble they may be, but even in our age of advanced technology, there's just no escape...