Fungi

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Chapter 14

• Fungi

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Importance of Fungi
Together with Heterotrophic bacteria
Ecological decomposers
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Root-rot fungus- white mycelial causes disease in
living trees Acts as decomposers on dead plants
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Decomposing fruit- Rhizopus
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Root rot Ouch!!!
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Fungi

• Composed of Hyphae

Chitin in cell wall

• Heterotrophic absorbers

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Characteristics of Fungi

• Composed of Hyphae
• Fungal filaments Cobwebby strands of
  subterranean white stuff

Mycelium
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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

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

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Four phyla of fungi

• Chytridiomycota
• Zygomycota
• Ascomycota next week lecture
• Basidiomycota next week lecture

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Chars of Fungi

• All have cell wall
• Cell wall composed of polysaccharide- chitin
• Chitin more resistant to microbial degradation
  than cellulose

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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

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Fungi obtain their food

• Either as Saprophytes
• or
• As mutualistic symbionts

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

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Fungi Store energy

• Polysaccharide
• Glycogen
• Lipids

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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

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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

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Asexual reproduction

• Or
• Hyphal cells called conidiogenous cells
• Spores produced by conidiogenous cells occur
  singly or in chains called conidia

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Asexual repro

• Some Reproduce by fragmentation of their hyphae

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Sexual reproduction

• Three distinct phases
• First two are phases of fertilization (syngamy)
• Plasmogamy- the fusion of protoplasts
• Karyogamy- the fusion of nuclei (some dont fuse
  forming a dikaryon)

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Give rise to gametes by differentiation
Divide by mitosis
gametangia
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Spores
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The last phase is meiosis

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

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Zygospores

• Zygospores
• Asexual and sexual reproduction (by means of
  haploid spores)
• Sexually producing zygospores require two
  compatible species

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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

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Life cycle of Rhizopus stolonifer
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Gametangia the gamete producing structures are in
the Process of producing a zygospore
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Zygospore develops within the thick walled
zygosporangium