Fungi (characteristics and function)

Taxonomy of fungi (eumycota)

Rapidly changing taxonomy 1) Chytridiomycota 2) Zygomycota* 3) Glomeromycota 4) Ascomycota* 5) Basidiomycota* 6) Microsporidia - practure -> groups distinguished by reproduction - based on molecular analysis - 90,000 species described - possible 1.5mil - fungi imperfect (older name still in use

Zygomycota examples

Rhizopus stolonifer (bread mold)

Superficial

black piedra (piedra hortae)

Ecological roles (and other)

1) Decomposers 2) disease agents 3) Symbiosis 4) Products and industries

Ascomycota - description

'ascomycetes' - cup fungi (ascocarp shaped commonly a cup) - mostly = saprophytes - few anima/plant pathogens - terrestrial and aquatic - includes yeasts and truffles

Zygomycota description

'zygomycetes - mostly saprophytes, few are plant/animal parasites, some industrial importance (food prod, antibiotics, drugs, meat tenderiser, yellow food colouring)

6) most are non-motile

- Exception: zoospores - chytrid have motile spores (affect frog species - zoospores swim and germinate, inbedding in frog's skin

4) Heterotrophic and osmotrophic

- Hetero: use reduced, preformed organic as organic carbon source - Osmo: soluble nutrients absorbed through cytoplasmic membrane - most fungi = Saprotrophic (derived nutrients from degradation of dead organic matter) - some (rare) fungi are predatory - some are pathogens of animals and plants - nematode: trapping fungus, plant tissue and animal tissue

Basidiomycota - description

- basidiomycetes, club fungi (zygote form) - most saprophytes - few are plant/animal pathongens - primarily terrestrial - includes many edible mushrooms - produce many toxic/hallucogenic compounds (mycotoxin)

5) spores

- both sexual and asexual spore may be reproduced - asexually on mycelium - sexually following mating

Decomposers

- break down complex macromolecules to simple - mineralise organic matter to C, N, P - convert organic matter to fungal biomass

3) Hyphal cell walls

- composer of chitin and glucan - Chitin: N-aceyylglucosamine (NAG) - Glucan: polysaccharide, polymer of glucose

7) Simple to complex life forms (asexual and sexual reproduction)

- cycles involving vegetative growth interspersed with asexual and/or asexual reproduction

Products and inudstry

- foods/ bevs - bread, win, beer, cheese - industrial chemicals - organisms, alcohols - pharmaceuticals - antibiotics (penicillin griseofulvin)

Symbiosis

- lichens: association btwn fungus (ascomycete) and age or cyanobacterium - mycorrhizae: assoc btwn fungus (ascomycete or basidiomycete) and plants

Disease agents

- plants - animals and humans (superficial, cutaneous, subcutaneous, systemic) - e.g. wheat stem rust (crop decrease 25%)

Sporagiospores

- produced by membrane inclosed 'sporangium'

Conidiospores

- spores borne on tips/sides of 'conidiospores' not enclosed membrane - paint brush

2) Basic unit is hyphae

- tubular masss branching filament - mass branching hyphae: mycelium - mycelium= type of thallus (vegetative structure or body of fungus) 1) aseptate (coenocytic): protoplasm streams throughout 2) septate: have a septum with pores to allow streaming

Characteristics of fungi

1) Eukaryotic (organelles - microfilaments/tubules) 2) Basic unit is hyphae - aseptate/septate 3) Hyphal cell walls composed of chitin and glucan 4) Heterotrophic and osmotrophic 5) produce spore 6) most are non-motile (zoospores) 7) Simple to complex life forms (asexual and sexual reproduction)

Asexual reproduction types

1) Hyphal growth (vegetative hyphen filaments transplanted or broken from body. can continue to grow) 2) asexual spore formation: - Sporangiospores - Conidiospores 3) budding (yeast)

Sexual reproduction

1) Plasmogamy: fusion of cytoplasm 2) heterokaryotic stage 3) Karyogamy: zygotes formed (fusion of nuclei) 4) meiosis (division of zygotes) 5) spore produced 6) germination of spores

Zygomycota characteristics

1) form coenocytic hyphae (containing numerous haploid nuclei) 2) sexual reproduction (requires compatible 'heterothallic', produce zygosporangium containing zygospores - thick, black, rough surface btwn hyphae branching)

Asexual reproduction

1) spore producing structures on mycelium 2) spores produced 3) spores germinate

Basidiomycota - characteristics

1) usually septate hyphae 2) asexual reproduction (heterothallic, produce basidiospore borne in basidia (S. basidium) on basidiocarps) 3) asexual reproduction = rare

Ascomycota - characteristics

1) usually septate hyphae 2) sexual reproduction: - Heterothallic (some self fertile i.e. homothalic) - produce ascospores borne in asci (s. 'ascus') on ascocarps 3) asecual reproduction is by formation conidiospores (conidia) on conidiospores 4) note: life cycle differs in yeasts)

Systemic

Histoplasmosis (Histoplasma capsulatum)

Subcutaneous

Sporotrichosis (sporotrichosis

Cutaneous

Tinea pedis (athletes foot)

Exceptions

Yeasts: -some are unicellular, bud and do not have mycelial stage (breads, beer) - some pathernogenic -> dimorphic - mycelial form outside host cell - yeast form in host Mold: fungi producing filamentous growth