Chapter 14

Fungi

Importance of Fungi

Together with Heterotrophic bacteria

Ecological decomposers

Decomposing fruit- Rhizopus

Root-rot fungus- white mycelial causes disease in living treesActs as decomposers on dead plants

Root rotOuch!!!

Fungi• Composed of Hyphae

• Heterotrophic absorbers

Characteristics of Fungi

• Composed of Hyphae

Fungal filaments= “Cobwebby” strands of subterranean “white stuff”

Mycelium

Fungi form important symbiotic relationships

• 80% of all vascular plants species from mutually beneficial associations called mycorrhizae between roots and fungi

• Plant nutrition

• Lichens form symbiotic relationship with fungi, algal, or cyanobacterial cells

• Fungi and insects

• Endophytes- fungi live in plants produce toxic that protect host

Four phyla of fungi

• Chytridiomycota

• Zygomycota

• Ascomycota next week lecture

• Basidiomycota next week lecture

Chars of Fungi

• All have cell wall

• Cell wall composed of polysaccharide- chitin

• Chitin more resistant to microbial degradation than cellulose

All Fungi Heterotrophic Absorbers

• Unable to engulf small microorganisms

• Secrete enzymes and absorb smaller molecules

•Absorb food mostly at or near the growing tips of their hyphae

Fungi obtain their food

• Either as Saprophytes

or

• As mutualistic symbionts

Some

• Obtain energy through fermenation producing ethyl alcohol from glucose (i.e. yeast)

Fungi Store energy

• Polysaccharide

• Glycogen

• Lipids

Fungi reproduce both sexually and asexually

• Reproduce through the formation of spores that are produced sexually or asexually

• Most are nonmotile spores• Some are dry and small and

airborne• Some are slimy and stick to the

bodies of insects and other arthropods

• Some propel into air- phototropism

Common method of asexual reproduction in fungi

• By means of spores

• Either produced in sporangia– The sporangium is a saclike structure, the

entire contents of which are converted into one or more spores

Asexual reproduction

• Or• Hyphal cells called conidiogenous cells

– Spores produced by conidiogenous cells occur singly or in chains called conidia

Asexual repro

• Some Reproduce by fragmentation of their hyphae

Sexual reproduction

• Three distinct phases

• First two are phases of fertilization (syngamy)– Plasmogamy- the fusion of protoplasts– Karyogamy- the fusion of nuclei (some don’t

fuse forming a dikaryon)

4

Divide by mitosis

Give rise to gametes by differentiation

gametangia

Spores

The last phase is meiosis

• Sexual reproduction results in the formation of specialized spores such as zygospores, ascospores, basidiospores.

Zygospores

• Zygospores

• Asexual and sexual reproduction (by means of haploid spores)

• Sexually producing zygospores require two compatible species

Zygomycetes: Phylum Zygomycota

• Live on decaying plant and animal matter in soil

• Some are parasites of plants, insects or small soil animals

• Others form symbiotic relationships- endomycorrhizea- with plants occasionally cause infection in animals

• Rhizopus stolonifer- best known zygomycetes

Life cycle of Rhizopus stolonifer

Gametangia the gamete producing structures are in the Process of producing a zygospore

Zygospore develops within the thick walled zygosporangium