Mycology

Structure of fungi

Basic Structure is hyphal
-a slender filament of cytoplasm and nuclei enclosed by a cell wall.
-a mass of hyphae made up mycelium. ( can permeate soil, water and living tissues so as to allow fungi to grow.)

Septa
-crosswalls that separate cytoplasm and nuclei into cells type of hyphae species.

Coenocytic(multinucleate)
-incomplete of no septa hyphae species.

Chitin(cell walls)
- the same polysaccharides that comprises the exoskeleton of insects and crustaceans.

Fungal Nutrition

Carbon nutrition
1)Saprotrophy (where fungi utilize dead plant, animal or microbial remains)
2)Parasitism (where fungi utilize living tissues of plants and animas to the detriment of the host)
3)Symbiosis (where fungi live with living tissues to the benefit of the host)

Saprophytic fungi
-Most carbon in the environment is not in a soluble form but is present as a complex polymer like cellulose, chitin or lignin.<< have to be broken down using enzymes before utilized.
-Soil and damp substrates so as to take in nutrients.

Parasitic and symbiotic fungi
-Carbohydrate must enter hyphae in a soluble form because of the rigid cell wall which prevents endocytosis. Soluble sugars cross the fungal wall by diffusion, followed by active uptake across the fungal membrane. -Needs to be in moist environment.

Temperature and pH required for fungi to grow
1) Most are mesophilic, grows between 5-40
2) Some are psychrophilic, grows under 5.
3)others are thermotolerant or thermophilic, grows over 50.

-Tends to occupy acidic environment and metabloic activity further acidify it, grows at pH 4-6.

Reproduction
1)Zygomycota
2)Ascomyota
3)Basidiomycota

1)Zygomycota
-Asexual reproduction begins with the production of aerial hyphae.
-Tip of the aerial hyphae (sporangiophore) is separated from the vegetative hyphae by columella(a complete septum)
-The contents of the tip differentiate into a sporangium containing many asexual spores
-Spores contain haploid nuclei derived from repeated divisions of a nucleus form the vegetative mycelium.
-Dispersal of spores is by wind or water.

=Sexual production is when two nuclei of differentamting type fuses together within a specilized cell called zygospore.
=Fusion between modified hyphal tips are called progametangia.
=Within developing, zygospore meiosis occurs; usually 3 of the nuclear products degenerate, leaving only 1 nuclear type preent in the germnating mycelium.

2)Ascomycota

-In Asexual reproduction, the production of single spores called conidia from the tips of aerial hyphae called conidiophores.
-Those spores are single-celled and contain one haploid nucleus or multi-cellular and contain several haploid nucleus.
-Spores can be produced from single unprotected conidiophores or from large aggregations.
-The conidiphores aggregrate into stalked structures.
-A certain amount of sterile fungal tissue is protecting the flask-shaped pycnidia.
-Different species produce different plant tissue and so the conidial aggregations that erupt through the plant-epidermis may be in different shape.

=Sexual reproduction occurs only after the fusion of different mating type of mycelia.
=The formation of ascospores comes after the transient diploid phase.
=The initial stage ofascal development is called croziers of shepherds’ crooks. They ensure that two different mating type nuclei are maintained in the cell.

3)Basidiomycota(rare to produce asexual spores)
-The aquistition of two mating types of nuclei by the fusion of compatible hyphae.
-Single representatives of the two mating-type nuclei are held within every hyphal compartment for extended periods of time.(dikaryotic state)
-The onset of sexual-spore formation begins with the formation of fruit body promordium.

How?
1)Dikaryotic mycelium expands and differentiates to form larger fruit bodies like mushroom.
2)Diploid formation and meiosis occur within a modified hyphal tip called a basidium.
• 4 spores are budded from the basidium
• Basidia form together and a hymenuim was created which was then distributed over the sterile,dikaryotic-supporting tissues which protects it from water.
• Hymenium can be seen on gills or pores beneath the fruit body or enclosed within chambers in puffballs and truffles.

USES

1)Food
• Mushroom. for example, button mushrooms

• Truffle
• Soya sauce which use Aspergillus oryzae or Saccharomyces rouxii
~~ Soya bean are soak and cook to remove contaminants then mixed with roasted wheat. The fungus Aspergillus oryzae is mix for about 20 to 40 hours at 25 C. It produces invertases, amylases and cellulases which degrade the soy paste. The paste is then mixed and second stage of fermentation take place. In deep vats, brine is added to the paste and the yeast Saccharomyces rouxii and lactobacilli are added. Anaerobic conditions develop quickly, preventing further growth of A. oryzae. After about a month, a sour liquid is apparent. The liquid contains large concentrations of amino acids, simple sugars and a range of vitamins. After separation and further storage, the liquid is sterilised, bottled and sold as Soy Sauce.
• Use in yeast for baking and brewing

• Cheese which use Penicillium roqueforti
~~stab-inoculated with a strain of Penicillium roquefortii
• Other flavours
~~ fungi are responsible for a range of flavours including terpenes, menthol and lactones. It could neutralise bitter taste. However, flavour enhancement is not so important.
• Colours, eg, Monoascus purpureus has been traditionally used for the production of red wine.

2) Medicine

• Antibiotics such as penicillin from the fungus Penicillium chrysogenum- treatment of infections caused by bacteria. Another example is cephalosporin.
• Production of other drug such as anti cholesterol drug.
• Immune Suppressants

3) Industries
• Enzymes:
~~lipases in detergent industry
~~glucose oxidase
• Organic acids -e.g. citric acid in Coke is produced by an Aspergillus
• Fermentation process is use in the production of alcohol and bread making.

4) Bio-pesticides
• Environmental friendly pesticides that are used to control pests using living organisms.
• Metarrhizium has been successfully used to control spittlebugs in South America, Rhinoceros beetle in the South Pacific islands, and in Australia to control locusts.
• Soil renewal through the decomposition of organic matter.

5) Plants

• Increase surface area of root- Although plants have tiny root hairs to aid absorbtion by increasing the surface area of the root, most plants also have a fungus associated with them that grows around the roots and in effect further increases the surface area of the roots. In many instances one species of fungus may be specific to one or only a few species of plant. Without these fungi many plants would die or be unable to grow properly.
• Fungi help plant to stay healthy. Fungi help plants to get minerals and waters.

6) Environment
• Fungi decompose plants, animals, litter and debris. Without fungi, dead plants and animals would just lie there forever.
• Along with bacteria, fungi are important in recycling carbon, nitrogen and essential mineral nutrient.

7) Research tools
• Fungi are important research tools in the study of biological processes because of how rapidly they grow.
• S. Cerevisiae was first eukaryotic organism to be sequenced