All living organisms are organised into large groups called Kingdoms. Fungi were originally placed in the Plant Kingdom then, scientists learned that fungi were more closely related to animals than to plants. Then scientists decided that fungi were not sufficiently similar to animals to be placed in the animal kingdom and so today fungi have their own Kingdom – the Fungal Kingdom.
The fungal kingdom is largely hidden from our view and we usually only see the “fruit” of a fungus. The living body of a fungus is called a mycelium and is made up of a branching network of filaments known as hyphae.Fungal mycelia are usually hidden in a food source like wood and we only know they are there when they develop mushrooms or other fruiting bodies. Some fungi only produce microscopic fruiting bodies and we never notice them.
Fungi feed by absorbing nutrients from the organic material that they live in. They digest their food before they absorb it by secreting acids and enzymes. Different fungi have evolved to live on various types of organic matter, some live on plants (Phytopthora infestans – the potato blight fungus) some on animals (the athlete’s foot fungus) and some even live on insects (Cordyceps australis).
Most of us use fungi every day without even knowing it. We eat mushrooms and Quorn, but we also prepare many other foods using fungi: The yeast Saccharomyces cerevisiae is a fungus and puts the bubbles in wine and beer and makes bread rise, also the koji process uses the fungi Aspergillus sojae and Aspergillus oryzae to produce the oriental foods, soy sauce and miso. We also use fungi to produce flavourings,
The antibiotic penicillin and cyclosporin Ð (a drug that stops organ rejection after transplantation) are both by products of fungi. Research scientists use several fungi to investigate basic functions that occur in all cells because they are simple and easy to grow; some fungi are used in cancer research.
Fungi are an essential part of the carbon cycle – responsible for breaking down dead organic matter which allows nutrients to be cycled through the ecosystem. Many plants cannot grow without the fungi that inhabit their roots and supply them with essential nutrients.
Without fungi we would not have bread, beer, wine or antibiotics, but more importantly without the nutrient recycling and plant nutrition provided by fungi – we probably could not survive at all.
Fungi that cause plant diseases result in the loss of billions of dollars a year due to crop-damage and post-harvest decay. Also, several fungi produce dangerous substances called toxins, which if eaten via contaminated food – can be fatal to man and other animals. This is particularly a problem in developing countries where crop contamination can result in severe famine – or if eaten gives rise to various forms of cancer including liver cancer. Contamination of corn with one toxin called aflatoxin, produced by the fungus Aspergillus flavus,costs farmers in the U.S. alone – $100 million annually.
In humans fungi cause relatively minor skin infections such as ringworm and athlete’s foot, but several types of fungi – whose spores are carried around in the air we breathe – also cause several deadly diseases which can be hard to treat. These types of fungi are not generally visible to the naked eye – but it is their airborne spores which can cause illness. Fungi that can cause life-threatening infections in people include Aspergillus fumigatus, and other Aspergillus species, Candida albicans and Cryptococcus neoformans.
Aspergillus infections can also cause an allergic type disease called – allergic bronchopulmonary aspergillosis (ABPA)- some asthmatics are known to be sensitised to aspergillus and can improve when treated with antifungal drugs, but symptoms for ABPA are usually lifelong. Estimates show around 650,000 patients suffer from ABPA in the US and UK alone.
The majority of patients who contract deadly fungal diseases may have undergone anti-cancer therapy, had a transplant or other serious infection or problem which results in a weakened immune system. They may have leukaemia or AIDS or they may be taking drugs to suppress their immune system because of organ transplantation. They are then vulnerable to contracting some fungal infections like aspergillosis and candidiasis – which may well be life threatening. There are some anti-fungal drugs to treat fungal infections but these can have some unpleasant side-effects, because they are often toxic to people as well as to fungi. Also, several fungi are now resistant to these anti-fungals and there is a desperate need for research to develop new and better antifungal agents.
Although the planet cannot survive without fungi, the harmful species can cause cause serious illness often fatally, in hundreds of thousands of people worldwide. The global burden of people needing treatment for aspergillus including allergic disease is around 3million.