In this article we will discuss about the useful and harmful activities of fungi.
Useful Activities of Fungi:
Directly or indirectly fungi are beneficial to human being. Fungi is used in medicine industry, as food, in food preparation, in other industry and also in agriculture. Some of the useful activities are:
1. Preparation of Medicine:
Various kinds of fungi are used in the production of various kinds of medicine. The most important members are Penicillium notatum, Claviceps purpurea, Saccharo myces cerevisiae, Eremothemium ashbyii, Aspergillus proliferous etc.
Antibiotics are the metabolic product of some microorganisms which are active against other microorganism(s). Sir Alexander Fleming (1929) was the first who invented the wonder drug Penicillin from Penicillium notatum.
Later, Penicillin was also commercially produced from P. crysogenum. Later on, other different types of antibiotics were isolated from different fungi. The list of some fungi along with their produced antibiotics and range of activity are given above.
Several alkaloids are produced and accumulated in the sclerotium of Claviceps purpurea which causes Ergot disease of rye. Out of several alkaloids, Ergo- metrine and its semisynthetic analogues like methyl ergometrine and methyl ergometrine maleate have prominent uterine action; those control haemorrhage of mother during child’s birth, having side- effect with increase in blood pressure and decreased milk secretion.
Rheumatic arthritis, allergy and some other diseases are controlled by steroid. Many fungi have the capacity to synthesize different steroids. Steroid like cortisone is produced by Aspergillus niger from plant glycosides by fermentation.
Vitamins are the micronutrients required for the growth of living organisms. Vitamin B-complex, Vitamin A and Vitamin B-12 are found respectively from Saccharomyces cerevisiae, Rhodo- torula gracilis and Eremothemium ashbyii.
(e) Other Compounds:
An anticancerous substance, calvacin is present in the giant PuffbalI (Clavatia gigan- tea), that prevents stomach tumours. Similarly, fungi like Ganoderma lucdum have promising significant roles in anticancerous, anti HIV and antihepatitis-B diseases. The fungi like Coriolus versicolor have also anticancerous activity.
Fungi are used as food by humans from prehistoric period. Some fungi have been used directly as food and some are used in food processing:
(a) Direct Use:
Fruit bodies of some fungi, like Agaricus brunnescens, A. campestris, Volveriella volvacea, V diplasia, Pleurotus sajor-caju, Lentinus edodes etc. are used as food due to their high protein content (21-30% on dry weight) and have good amount of lysine, an amino acid; minerals like Na, Ca, K and P; Vitamins like B, C, D and K and very little amount of fat.
These are recommended as ideal foods for heart and diabetic patients. The above fungi can also grow artificially at commercial level.
(b) Used in Food Processing:
The nutritious food soyabean cannot be digested easily by human beings.
Soyabeans are fermented by fungi like Rhizopus oryzae, R. oligospo- rus to prepare an easily diges- table and tasty food known as “tempeh”.
Several Indian foods such as jalebies, idli, murcha, papadam and toddy, are actually the fermented products caused by several fungi like Saccharomyces bayanus for jalebies; Tricho- sporon pollulans and Torulopsis Candida for idli; Rhizopus arrhizus for murcha; Saccharomyces cerevisiae for papadam and toddy.
Fermentation by yeast, particularly by Rhodotorula and Saccharomyces, results in quick growth of the organism producing single cell protein (SCP). Because of high nucleic acid content, the fermented products are not suitable for human nutrition, but can be used as feed for animal.
3. Fungi in Industry:
Many fungi are used in the production of alcohol, bread, cheese, enzyme and organic acids.
(a) Alcohol Production:
Alcoholic fermentation by fungi is the basis of brewing industry. The enzyme zymase of microorganisms like yeast is responsible for alcohol production.
The reaction is:
Wines are produced from grapes or other fruits by Saccharomyces ellipsoideus with about 14% alcohol concentration. Beer is brewed from barley malt by Saccharomyces cerevisiae with 3-8% alcohol production.
(b) Bread and Cake Production:
During alcoholic fermentation by yeast, CO2 being released as bubbles are used in baking industry to make the breads and cakes as spongy in appearance.
(c) Cheese Production:
Some species of Penicillium (P. roquiforti and P. camemberti) are used in the production of Roquefort and Camembert cheese by hydrolysis of fats and also to develop specific flavour to cheese.
(d) Enzyme and Organic acid Production:
Many fungi are used in the commercial production of enzymes and different organic acids.
List of some fungi along with produced enzymes and/or acids and their uses are given:
4. Soil Fertility:
Decomposition of litter and wood, mainly in the forest, takes place by the combined action of different type of fungi. Fungi like Fusarium, Chaetomium, Chitridium, Penicillium, Aspergillus etc., can decompose the structural polymers such as cellulose, hemicellulose, lipid, protein, starch etc.
The more recalcitrant (persistant) polymers like lignin are decomposed by white rot fungi of Basidiomycotina. By decomposing the organic matters, fungi help to increase minerals and other substances, thereby the fertility of soil is increased.
5. Plant Nutrition:
Several fungal members like Rhizoctonia, Tricholoma, Boletus, Phallus, Amanita etc., associated with the roots of higher plants form mycorrhizal relationship. The fungal partner supplies water and minerals and in turn, they take nutrition from the plant.
6. Manufacture of Phytohormone:
Gibberellin, an important phytohormone produced by Gibberella fujikuroi, the pathogen of Bakanee disease of rice, has been used to enhance growth of many plants.
7. As Insecticide:
Fungi like Cordyceps melonthae, Aschersonia aleyroidis, Empusa sepulchralis etc., are used as insecticides to control different types of insects.
8. Biological Research:
Fungi like Neurospora, Yeast etc., have been used in genetical and cytological studies. Physarum polysephalum has been used to study DNA-synthesis and morphogenesis.
9. Test Organism:
Some strains of Aspergillus niger have been used to detect trace elements like Zn, Cu, and Mo, even if the substances are present in very minute quantity in the substrate. These elements when absorbed by the fungus give a particular colour to the conidia. Similarly, Neurospora crassa has been used to detect Vitamin B complex.
Harmful Activities of Fungi:
Fungi are also harmful to the human beings in various ways, either directly or indirectly. They may cause diseases of plants, human beings, and animals; spoilage of food etc.
Some of the harmful activities are:
1. Fungi Causing Plant Diseases:
Fungi cause several minor and major plant diseases. Some of them also cause famine in different parts of the world.
List of some diseases along with causal organism are given:
2. Fungi Causing Human Diseases:
Like plant disease, some fungi also cause human diseases.
Some of the important human diseases caused by fungi are given:
3. Fungi Causing Animal Diseases:
Like plants and human being, some animals also suffer from different diseases caused by fungi.
Some important animal diseases caused by fungi are given:
Besides above diseases, Saprolegnia parasitica, an aquatic fungi live as parasite on egg and gills of fishes. Members like S. ferax, Achlya sp. and Ichthyophorus haferi cause severe damage to fishes.
4. Fungi Causing Disease of Vegetables and Fruits:
Different species of fungi cause disease (post-harvest) in vegetables and fruits.
List of some commonly available diseases are:
5. Spoilage of Food:
Different types of food are destroyed by different fungi like Mucor, Aspergillus, Penicillium, Rhizopus etc.
Some of them are given below:
6. Destruction of Timber:
Species of Polyporus and Armillaria are very common — cause wood rot of many trees. Polyporus abietinus causes decay of Abies wood, P. schweinitzii causes bud rot of mature conifers, P. sulphureus causes wood rot of apple, pear etc., while Armillaria mellea causes red rot of apple.
7. Destruction of Goods:
Fungi like Alternaria, Mucor, Trichoderma, Penicillium, Chaetomium, Cephalothecium etc., destroy paper, rubber, leather, camera lenses etc. In addition to the above, other fungi like Chaetomium globosum, Memnoniella echinata destroy jute products.
8. Poisonous Fungi:
Some fungi like Amanita phalloides produce toxins, like α-amanitin causes lesions of stomach cells and phalloidin affects on liver. Fungi, like Aspergillus flavus, A. fumigatus and Penicillium islandicum when infest ground nut and mustard cakes, produce a poisonous substance, the aflatoxin that binds with DNA and inhibits transcription, resulting into the inhibition of protein synthesis.
9. Hallucinogenic Drug:
LSD (d-lysergic acid diethylamide), the well-known hallucinogenic drug, is extracted from the sclerotia of Claviceps purpurea, the causal agent of ergot disease of rye. Other fungi like Psilocybe mexicana produce Psilocin and Psilocybin that have hallucinogenic properties. The hallucinogenic substances may destroy brain cells and cause distortion of perception power of human beings.