Chapter 14
Fungi
Importance of Fungi
Together with Heterotrophic bacteria
Ecological decomposers
Decomposing fruit- Rhizopus
Root-rot fungus- white mycelial causes disease in living trees
Acts as decomposers on dead plants
Root rot
Ouch!!!
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 airphototropism
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)
Divide by mitosis
Give rise to
gametes by
differentiation
gametangia
4
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 relationshipsendomycorrhizea- 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