1. FUNGI Fungi comprise of molds and yeasts Characteristics of fungi: 1. Eucaryotic 2. Chemoorganotropic (require organic compounds for nutrition) and do not have chlorophyll. The thallus or body of fungus may consists of single cell as in the yeasts; more typically the thallus consists of filaments 5 to 10 μ across. The yeast cell and molds filament is surrounded by a true cell wall (the exception being the slime molds, which have a thallus consisting of a naked amoeboid mass protoplasm) Morphology: Yeast: In general yeast cell are larger than most bacteria. Yeasr vary considerably in size, ranging from 1 to 5 μm width 5 to 30 μm more in length. They are commonly egg- shaped but some are elongated and some spherical. Each species has a characteristic shape, but even in pure culture there is considerable variation in size and shape of individual cells depending on age and environment. Yeast has no flagella or other organelles of locomotion. Molds: The thallus of a mold consists essentially of two parts: the mycelium (plural mycelia) and the spores (resistant, resting or dormant cells). The mycelium is a complex of several filaments called hyphae (singular hypha). New hyphae generally arise from a spore which on germination puts out a germ tube or tubes. These germ tubes elongate and branch to form hyphae.

2. Hyphae are composed of an outer tube like wall surrounding a cavity the lumen which is filled with protoplasm. Between the protoplasm and the wall is plasmalemma, a double layered membrane which surrounds the protoplasm. The hyphal wall consists of microfibrils composed for the most part of hemicellulose or chitin, true cellulose only in the walls of lower fungi. The chemical composition of fungal cell walla varies between species as well as with age and morphology of the fungus. The wall is composed of 80 to 90% carbohydrate, the rest being proteins and lipid, and in some cases sterol. The main structural polysaccharides include cellulose, chitin, mannan and glucan; the integral structures differing from the cell walls of bacteria but resembling those of higher plants. The young hyphae may become divided into cells by cross walls which are formed by inward growth from the existing cell wall. These cross walls grow inward to form generally incomplete septum that has a central pore which allows for protoplasmic streaming. Even nuclei may migrate from cell to cell in hyphae. Hyphae occur in three forms: Nonseptate or coenocytic Septate with uninucleate cells Septate with multinucleate

3. Mycelia can be either vegetative or reproductive. Some hyphae of the vegetative mycelium penetrate into the medium in order to obtain nutrients, Soluble nutrients are absorbed through the walls (insoluble nutrients first digested externally by secreting enzymes). Reproductive mycelia are responsible for spore production and usually extend from the medium into the air. The mycelium of a mold may be loosely woven network or it may be an organized, compact structure, as in mushrooms. Reproduction: Fungi reproduce naturally by a variety of means. Asexual reproduction (also called somatic or vegetative reproduction) does not involve the union of nuclei; sex cells or sex organs. It may be accomplished by (1) fission of somatic cells yielding two similar daughter cells, (2) budding of somatic cells or spores, each bud a small outgrowth of the parent cell developing into a new individuals; (3) fragmentation or disjointing of the hyphal cells, each fragment becoming a new organism, or (4) spore formation.

4. Asexual spores Asexual spores, whose function is to disseminate the species, are produced in large numbers. There are many kinds of asexual spores. 1. Sporangiospores: These single-celled spores are formed within sacs called sporangia at the end of special hyphae. Aplanospore : Nonmotile Zoospore: motile 2. Conidiospores or condia: (singular conidium) Small single- celled conidia are called microconidia. Large mutilcelled conida are called macroconidia. Conidia are formed at the tip side of a hypha. 3. Odia (Singular odium) or artrhospores. This single-celled spores are formed by disjointing hyphal cells. 4. Chamydospres : These thick-walled, single-celled spores are highly resistant to adverse conditions. They are formed from cells of vegetative hyphae

6. Sexual reproduction Sexual reproduction is carried out by fusion of compatible nuclei of two parent cells. The process of sexual reproduction begins with the joining of two cells and fusion of their protoplasts (plasmogamy) thus enabling the two haplpoid nuclei of two mating types to fuse together (karyogamy) to form a diploid nucleus. This is followed by meiosis, which again reduces the number of chromosomes to the haploid number. The sex organelles of fungi, if they are present are called gamentangia (They may contain differentiated sex cells (gametes) or may contain instead one or more gamete nuclei. If the male and female gametangia the male gametangium is called antheridium (plural antheridia) and the female gametangium is the Oogonium (plural oogonia). Various method of sexual reproduction include : Gametic copulation : Fusion of naked gametes, one or both of which are motile Gamete-gametangial copulation: Two gametangia come into contact but do not fuse. The male nucleus migrates through a pore or fertilization tube Gamaetangial copulation Somatic copulation

8. Sexual spores Ascospores: These are single-celled spores are produced in a sac called ascus. In the sexual phase ascogonium receives male nuclei form the antheridium where the nuclei pair but do not fuse. The ascogonium now gives rise to ascogenous hyphae where each cell contain two nuclei. Ultimately one of the tip cell of the hyphae transformed into ascus where the male and female nuclei fuse to form a diploid nucleus. This nucleus then undergo meiosis and gives rise to 4 haploid nuclei. These haploid nuclei divide once more by mitosis, forming 8 ascospore. Basidiospore : Nuclear fusion and meiosis take place in the basidium. Basidiospores are then formed exogenously at the tips of special outgrowth called sterigmata. Usually four spores are formed one at the tip of each sterigma. http://leavingbio.net/FUNGUS/Fungi2.htm#Economic http://bugs.bio.usyd.edu.au/learning/resources/Mycology/Struct ureFunction/spores.shtml

9. Industrial importance of fungi Textile Industry 'Amylases' isolated from bacteria, fungi, pancreas and malt are used in textile industry as softening agents for starched clothes. Starch is often added to cotton fibres as a stiffening agent, before weaving the fibre into cloth. Since, a starched cloth does not take good colour, the cloth is to be destarched before dyeing it. This is done with an amylase preparation, which hydrolyses starch). Leather industry Proteolytic enzymes from certain bacteria and fungi are used in the manufacture of leather. These enzymes digest the collagen or connective tissue holding the hairs to the hide in the skin and thus cause dehairing of the skin. These enzymes are also used for softening or plumping of dehaired skin, a process popularly called bating. ALCOHOL ► During anaerobic conditions, yeast ferments sugar to produce alcohol, carbon dioxide and water in the process of fermentation. Citric acid: Citric acid is produced by Aspergillus niger

15. Fungi are agents of biodegradation and biodeterioration : –SAPROTROPHIC fungi utilise dead organic materials as sources of nutrients and are responsible for the biodegradation of organic materials in our environment, particularly plant materials in the form of leaf litter and other plant debris. Such fungi play a vital role in recycling essential elements, particularly carbon. –Fungi are very effective and efficient biodegraders because of the wide range of EXTRACELLULAR ENZYMES they produce, which are capable of degrading complex polymers, such as cellulose, proteins and lignins.EXTRACELLULAR ENZYMES –Unfortunately, their excellent biodegradative abilities mean that many saprotrophic fungi are capable of contaminating our food sources or destroying many consumer goods we manufacture from natural raw organic materials. –

16. –For example, some saprotrophic fungi are particulalry dangerous contaminants of seeds and grains because they produce metabolites known as MYCOTOXINS (fungal toxins). When ingested mycotoxins cause toxic or carcinogenic symptoms in humans and other animals. Some Aspergillus species produce a group of chemically related mycotoxins calledMYCOTOXINS –A second example is provided by the 'dry rot' fungus, Serpula lacrymans, which attacks wood and can be a very costly, potentially dangerous and certainly most unwelcome visitor when it attacks timbers used in the construction of buildings (e.g. floor and wall joists or roof timbers).

17. Fungi are responsible for the majority of plant diseases and several diseases of animals (including humans) –For example, Phytophthora infestans is the causal agent of late blight disease in potatoes. The disease reached epidemic proportions across Europe in the mid 19th century and resulted in the Irish potato famine. –Some fungi are actively parasitic in humans and other animals, while others induce severe allergic reactions if their spores are inhaled - resulting in attacks of asthma or hay-fever.

18. Some fungi prove highly beneficial in agriculture, horticulture and forestry: –For example, some species form symbiotic relationships with the roots of plants, known as MYCORRHIZAS. Mycorrhizas significantly improve plant growth and vigour, resulting in increased yields in crop plants. –Other fungal species are used in the biological control of insect and nematode pests, weeds and pathogenic microorganisms. For example, the fungus Beauvaria bassiana is used to control a number of insect pests.