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KINGDOM EUMYCOTA - The
Zygomycetes (Order Mucorales)
- Hyphae are non septate and coenocytic (i.e., non-septate - no
- Cell walls contain
- Flagellated spores are absent.
- Reproduce asexually by producing
sporangiospores within a special sac called the
- Sporangium types (4 types)
True sporangium - refer to Figure 4-1 on
page 83 in the textbook
- Sporangioles - much smaller than true sporangia. No columella
produced and few spores - refer to Figure 4-6
on page 89 in the textbook.
- Monosporous sporangium (one-spored sporangium)
- refer to Figure 4-7b on page 90 in the textbook.
Merosporangium - sac containing 10-15 sporangiospores that occur in
a linear sequence - superficially it looks a lot like an ascus, but it
- Sexual spores are called zygospore(s) contained within a zygosporangium
(Refer to Figures 4-2 and 4-3 on pages 85 and 86 in the textbook).
- A. F. Blakeslee in 1904 discovered that many of these fungi are
heterothallic, that is, they require two compatible partners to produce
- Sex hormones are known to facilitate sexual reproduction among some
zygomycetes. For example, hyphae of Mucor species for the +
and - mating strains are known to produce trisporic acids which are volatile
(+ strain yields 4-hydroxymethyltrisporates; - strain yields trisporins) and
diffuse through the air. Volatiles stimulate progametagia production and
the synthesis of carotene (a precursor for trisporic acids) and trisporic
acids. A positive feedback mechanism is formed between the two compatible
strains leading to physical contact of progametagia and sexual reproduction
- refer to the pages 314-315 in the textbook.
- Heterothallism (Gr. heteros = different from, thallos
= shoot; the condition of being self-sterile, requiring a partner for sexual
reproduction) and homothallism (Gr. homos = alike, thallos
= shoot; the condition of being self fertile; able to reproduce sexually
without a partner) exhibited among species in this phylum.
- Two major classes
- members of this group are the "weeds" of the fungal world
- common genera include Mucor, Absidia, Rhizopus, and
- grow and invade quickly on easily digestible substrates, such as those
containing starches, sugars, and hemicelluloses
- group lacks ability to degrade complex carbohydrates like cellulose
- some are mycorrhizal, especially on monocots
- can act as parasites and/or cause diseases in plants (soft rot of fruits
and vegetables), animals (predatory on nematodes and some insects and humans
(zygomycosis - sometimes referred to as mucormycosis or phycomycosis)
- In humans, such diseases are opportunistic and occur in an
immunocompromised person (e.g., uncontrolled diabetes, AIDS)
- Industrial uses of these fungi include production of metabolites (e.g.,
amylases, rennins, alcohol, and various organic acids - lactic acid, citric
acid, succinic acid, oxalic acid)
- Growth of fungi used to modify foods, in production of tempeh or tempe
and Chinese cheese (sufu) - refer to pages 538-539
in the textbook.
- Rhizopus oligosporus is used to partially digest the proteins
of soybeans. The result is a food product called tempeh (produced in
Indonesia, New Guinea and Surinam), which is nutritionally enriched
(increased digestibility of proteins, higher levels of riboflavin,
niacin, and B12)
- How to make Tempeh:
- Soybeans are soaked overnight and dehulled.
- Soybeans are cooked by boiling for 1/2 hour.
- After cooling, beans are inoculated with Rhizopus
oligosporus by adding pieces of tempeh from a previous
batch, using a wrapper from former batch, or by adding a spore
suspension in water from a culture
- The beans are wrapped (e.g., leaves, plastic) and then
incubated at room temperature for about 24 hours
- Tempeh is sliced, dipped in salt water and cooked.
- Mucorales Lab Exercise: MS Word
Phototropism of the sporangiophore and dispersal of the explosive dispersal
of the sporangium - - refer to pages 338-342
in the textbook.
Zygomycetes (Order Entomophthorales)
- Members of this order are predominately parasites
of insects and other arthropods
- Entomophthora (more than 40 species
recognized) and Massospora are insect parasites
- Entomophthora muscae kills house flies.
- Flies are sometimes found attached to window
panes, surrounded by a halo of sporangia (sometimes referred to as
conidia) that are forcibly discharged from sporangiophores which emerge
between the abdominal segments.
- Fungus invades insect after contact with
sporangium. A germ tube forms and penetrates the host. Insect becomes
restless and exhibits behavioral changes.
- After 5 to 8 days, host crawls to elevated
position (e.g., blade of grass, twigs, window panes, etc.) Death often
occurs between 3:00 to 7:00 pm.
- Host is attached to surface by rhizoids,
sporangiophores form and push out between the abdominal segments
sporangia are forcibly discharged as turgor pressure builds up in the
sporangiophore. The sporangium may be shot as far as 1.0 to 1.5 cm away
- Entomophthora muscae:
Dispersal of the explosive dispersal of the sporangium -
refer to Figure 12-5b page 342 in the textbook.
- Zygospores may form within the body cavity of
- Links to photographs and other information on
- Massopspora cicadina is a parasite on the
17 year locust.
- Sporangia are produced in clusters with the
body cavity in the abdomen that are not forcibly discharged.
- Later infections, posterior portions of the
abdomen drop away successively, exposing sporangia.
- Insect will continue to fly around with only a
head and thorax.
- Zygospores my form with the abdomen with time.
- Entomophthora coronata (AKA
Conidiobolus coronatus) - parasitic on humans, horses and insects.
In humans, subcutaneous infection is called Entomophthoromycosis
- Basidiobolus ranarum is associated with the
dung of frogs and represents a saprophyte.
- Sporangia (AKA conidia) are forcibly
discharge. Turgor pressure created by contraction of the elastic
sporangiophore wall causes a tear in the sporangial wall lifting the
sporangium away from the dung. The sporangium and "skirt" travel about
0.5 cm. The skirt detaches from the sporangium and the sporangium
continues to travel an additional distance of 1-2 cm. This form of
explosive "spore" dispersal has been referred to as a "two stage rocket"
form of propulsion created by the rushing of fluid out of the expelled
skirt. Momentum carries the sporangium the remaining distance.
- This fungus also produces sporangioles (also
called capilliconidia with haptor) which are sticky and catch onto
passing insects, like beetles. The fungus is thought to re-enter the
amphibian or reptiles digestive track when the animal eats a tainted
beetle. In the stomach the capilliconidia cleaves into a number of
spores. Upon voiding their excrement, the fungus mycelium grows and
produces more sporangia (AKA conidia) and sporangioles (AKA
- Disease is called Entomophthoromycosis
Basidiobolae (a form of zygomycosis in humans in which tumor like
enlargements develop in the subcutaneous tissue) was once thought to be
caused by a species other than Basidiobolus ranarum (called
Basidiobolus haptosporus). However isolates obtained from
infected tissues in humans appears to be B. ranarum and not a
distinct separate species.
- Basidiobolus: Dispersal of
the explosive dispersal of the sporangium; the two stage rocket -
refer to Figure 12-5a on page 342 in the textbook.
Entomophthoromycosis Conidiobolae and
Entomophthoromycosis Basidiobolae represent forms of zygomycosis
(fungal diseases caused by zygomycetes).
Trichomycetes (Obligate commensals of arthropods)
- refer to pages 96-101 in the textbook.
Figure A: "Trichospores" - one-spored
Figure B: "Zygospores" - one-spored
Figure C: A zygospore - a one-spored
The web page is
maintained by Dr. Martin Huss. Last updated: October 4, 2007