Mycology Lecture Notes PDF

Mycology Dr. Bahroz A. Mahmood BVM&S, MSc, PhD  Introduction to mycology ▪ The term "mycology" is derived from Greek word "mykes" meaning mushroom. Therefore mycology is the study of fungi. ▪ Mycology is a part of biology that describes and concerned with the systematic s...

Mycology Dr. Bahroz A. Mahmood BVM&S, MSc, PhD  Introduction to mycology ▪ The term "mycology" is derived from Greek word "mykes" meaning mushroom. Therefore mycology is the study of fungi. ▪ Mycology is a part of biology that describes and concerned with the systematic study of very vast group of organisms called fungi. ▪ It describes genetic and biochemical properties taxonomy, and applications of fungi to humans as a source of medicine (e.g., penicillin), food (e.g., beer, wine, cheese , edible mushrooms), as well as their dangers, such as poisoning or infection.  What are fungi? Fungi ( singular Fungus), is a type of eukaryotic organism belonging to the kingdom Fungi, alongside plants, animals, protozoa, and monera. Fungi are incredibly diverse, with commonly encountered forms including yeast, molds, truffles, and mushrooms.  Fungi are heterogeneous, unicellular(yeast) to filamentous multicellular (mould) , spore bearing, and chemoorganotrophic organisms which lack of chlorophyll. Fungi inhibit almost every niche in the environment and humans are exposed to these organisms in various fields of life. Fungi are a unique group of organisms, different from all others in their behaviour and cellular organization. Distribution and abundance Fungi are either terrestrial or aquatic, the latter living in freshwater or marine environments. Freshwater species are usually found in clean, cool water because they do not tolerate high degrees of salinity. Soil that is rich in organic matter furnishes an ideal habitat for a large number of species; only a small number of species are found in drier areas or in habitats with little or no organic matter. Fungi are found in all temperate and tropical regions of the world where there is sufficient moisture to enable them to grow. About 144,000 species of fungi have been identified and described, but mycologists estimate that there may be between 2.2 million and 3.8 million total species.  Commonly used terms in mycology Mycology: the study of fungi. Molds: fungi which exhibit filamentous type of growth. Yeasts : fungi which exhibits pasty or mucoid form of fungal growth. Heterotrophic: they require organic nutrients as a source of energy like in (animal and most of bacteria). Saprophytes: live on dead organic matter. Pathogens: cause disease in humans or other organisms Hypha: fundamental tube-like structural units of fungi. Spore: generally the reproductive body of a fungus; occasionally, a resistant body for adverse environment. Zoophilic: dermatophytes which are parasitic on lower animals as well as human. Fungemia: fungal blood infection  Continued… ▪ Mycelium mas of hyphae forming the vegetative portion of the fungus. ▪ Aerial hyphae: growing or existing in the air. ▪ Vegetative hyphae: - absorbs nutrients. ▪ Fertile hyphae: bears conidia (spores) for reproduction. ▪ Sporulation: preferred terms when there is a merging of nuclear material. ▪ Self fertile: are termed homothallic. ▪ Mating types: are termed heterothallic.  Importance of fungi Medicine; many antibiotics are derived from fungi such as penicillin from penicillium. Vitamin sources; Vitamin B-complex, Vitamin A and Vitamin B-12 are found respectively from Saccharomyces cerevisiae. Recycling; with aid of bacteria, fungi are responsible for recycling of dead material to soil in the form which can be used again. Source of food; fungi can be used as source of food such as many kinds of(mushroom and truffle) and Quorn (mycoprotein ). Biological control; some fungi are used as biological control by parasitizing the causative agent of some crop diseases such as (Chinese caterpillar fungus)  importance of fungi continued… Biosynthetic activity; fungi can be used for production of alcohols, fats, citric, oxalic and gluconic acids by their fermentation properties. Model organism; because they are eukaryotic, fungi can be used as animal model for biochemical, molecular and genetic studies Soil fertility; Decomposition of litter and wood, mainly in the forest, takes place by the combined action of differ rent type of fungi. Fungi like Fusarium, Penicillium, Aspergillus. As Insecticide: Fungi like Cordyceps sp., are used as insecticides to control different types of insects. 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.  Harmful effects of fungi Animal and human diseases, including allergies. Toxins produced by poisonous mushrooms and within food (Mycetism and Mycotoxicosis). Plant diseases. Spoilage of agriculture produce such as vegetables and cereals in the storage. Damage the products such as magnetic tapes and disks, glass lenses, bones and wax. Destruction of food, lumber, paper, and cloth.  Virulence Factor of medically important fungi Despite the role of immune system of the host which plays an important role in causing infection by fungi, some virulence factors which listed below will make it easier for fungi to establish infection: ▪ The size of an organism (Disease that begins by inhalation requires that the organism be small enough to reach the target organs. ▪ The ability of an organism to grow at 37° C at a neutral ph. ▪ Conversion of the dimorphic fungi from the mycelial form to the corresponding yeast or spherule form within the host ▪ Possibly, toxin production.  General properties of fungi They are eukaryotic cells contain all membrane bound cell organelles Have a rigid cell wall and are therefore non-motile They are chemoheterotrophs. They require organic compounds for both carbon and energy sources. They are osmotrophs – They obtain their nutrition by absorption. Fungi are achlorophyllus i.e. lack chlorophyll pigments and are incapable of photosynthesis. Fungi exhibit the phenomenon of alteration of generation. They have both haploid and diploid stage. General properties of fungi continued… Fungi may be unicellular (yeast) or multicellular (moulds). All fungi are Gram Positive. Most are aerobic and facultative anaerobic. Very few fungi are anaerobic. Reproduction may be sexual ,asexual or parasexual.Many fungi reproduce both sexually and asexually. Pheromone is a chemical substance produced by fungi, which leads to the sexual reproduction between male and female fungi cells. Food storage is generally in the form of lipids and glycogen. Optimum temperature of growth for most saprophytic fungi is 20-30°C while (30-37)°C for parasitic fungi.  Nutrition and growth of fungi Fungi are chemoorganoheterotrophic organisms, They use chemical compounds as a source of energy and organic compounds as electron and carbon source. They obtain nutrition by absorption (osmotrophic) either from the environment(saprophyte) or the host (parasite). Most of the saprophytic moulds grow aerobically on artificial culture medium at 20–30 c. The pathogenic yeasts and yeast phase of dimorphic fungi prefer to grow at 37 c Fungi requires high humidity, acidic pH(3.8–5.6), high sugar concentration (4–5 %), carbon, phosphorus, sulphur and traces of potassium.  Physiology of fungi Fungal physiology refers to the nutrition, metabolism, growth, reproduction, and death of fungal cells. It also generally relates to interaction of fungi with their biotic and abiotic surroundings, including cellular responses to environmental stress. The physiology of fungal cells impacts significantly on the environment, industrial processes, and human health. In relation to ecological aspects, the biogeochemical cycling of carbon in nature would not be possible without the participation of fungi acting as primary decomposers of organic material. Furthermore, in agricultural operations fungi play important roles as mutualistic symbionts, pathogens, and saprophytes, where they mobilize nutrients and affect the physicochemical environment, or can be exploited as agents of biocontrol or as biofertilizers