One of the consequences of the recent wet weather is the appearance of mould. In fact mould is an ever present form of fungus; its spores are in the air and on surfaces waiting for the right conditions to germinate. The spores are microscopic eggs (3-40 microns) most float and travel great distances in the air, some species live in fresh water. The spores remain viable for decades until suitable hatching conditions are encountered. While there is variation, for many mould species ideal conditions are relative humidity above 60%, temperatures between 10-32 degrees C and pH 3-8 and when these occur and damp organic material (material that contains carbon atoms), is present the mould reproduces rapidly.
Mould spores contain DNA within a hardened case. When they float into a dry surface they rebound back into the air, but when they float onto a wet surface they grip and stick. The spore opens and a single multicelled organism emerges. The body grows a branching filament arm called hyphae, this hyphae grows another, then another until a huge network of hyphae is grown. The hyphae excrete digestive enzymes, which can break down complex organic material; the nutrients are absorbed by the hyphae and transported back to the central body. The nutrients may contain toxins, which the mould expels by spraying out aerosols such as carbon dioxide, alcohols etc and it is this process which produces a musty odour. The mould colony which becomes visible to the human eye is an interconnected network of hyphae called a mycelium. Most moulds reproduce by forming large volumes of spores produced either sexually or asexually depending on the species, fragments of vegetative hyphae may also form new individual moulds.
Mould is a fungi, this is a kingdom of organisms which are neither plant nor animal. Visible fungus includes mushrooms, yeast, mould, mildew, puffballs and bracket fungi. Fungus accounts for approximately one quarter of the planet's biomass. Plants and algae contain chlorophyll and can utilise the sun's energy to produce their own food in a process called photosynthesis, they are autotrophs. Since fungi do not contain chlorophyll they are unable to produce their own food through photosynthesis. Like animals they are heterotrophs and must absorb nutrients from dead, decaying and living organic matter.
Moulds are utilised by humans in a wide variety of food and drug production. Most notable was the discovery that Penicillium genus of mould inhibited bacterial growth; this led to the development of the antibiotic drug called Penicillin. Since then other mould based drugs such as the immunosuppressant cyclosporine have been developed.
But that is not the only benefit. Mould plays a key role in the decomposition, degradation and recycling of nutrients by changing them from complex materials to simpler substances, which are then available to be released back into the environment.
We may not like mould but we could not live without it.