Group of fungi characterized by their production of sexual spores in a sac-like structure called an ascus.
products of meiosis contained in a sac called an ascus
well-developed mycelium with septa at regular intervals
septa with simple pores (sometimes numerous micropores) & Woronin bodies
haploid w. restricted diploid life cycle asexual reproduction by conidia
Polysporous Asci (From David Geiser)
yeast powdery mildew
cup fungi many of these produce spores suited for
airborne dispersion.
Non motile
•Form ascospores Internally in Asci
•Most are blue-green, red and brown molds that cause food spoilage
•Penicillin
Ascomycetes Eyelash cup, Scutellinia scutellata
Brown rot of stone fruits (Monilinia fructicola)
•chestnut blight (Cryphonectria parasitica)
Many Yeast are also ascomycetes
•Edible Morels and truffles
Edible black truffle, Tuber melanosporum spore-bearing structure is produced below ground mainly on oaks and hazelnuts
Edible Ascomycete
Most have either unicellular or filamentous growth forms
Hyphae have perforated septa
Hyphal cells of Vegetative mycelim may be either uninucleated or multinucleated
Some are homothallic others heterothallic
Most species undergo asexual reproduction by the formation of multinucleated conidia
Conidia formed from the conidiogenous cells
Conidiogeneous cells are borne at the tips of modified hyphae called conidiophores “conidia bearers”
Conidia- the characteristic asexual spores of ascomycetes shows the stages in the formation of conidia which infects the velvetbean caterpillar
Penicillium sp
Aspergillus sp
TEM of Various stages of developments of conidida
Unlike zygomycetes which produce spores internally within a sporangium, ascomycetes produce their asexual spores externally as conidia.
dikaryotic stage is not usually of long duration
after karyogamy, meiosis occurs immediately to produce 4, 8, or more ascospores in an ascus
ascospores are formed by free cell formation within the ascus
Always involves the formation of an ascus (pl. asci)- saclike structure within which a haploid ascospores are formed following meiosis.
Because the ascus resembles as sac, commonly referred to as “sac fungi”
Both the asci and ascospores are unique structures that distinguish the ascomycetes from all other fungi
Ascus formation usually occurs within a complex structure composed of tightly interwoven hyphae- the ascoma (pl. ascomata) or ascocarp.
Maturing ascospores in Asci of Ascodesmis nigricans
Enclosed asci and ascospores of Ascoma called a cleistrothecium
An ascoma of Coniochaeta showing the enclosed asci and ascospores
Perithecium- fruiting body contains ascospores
“Dead mans fingers”
Perithecium with ascospores
Finger Xsec
Asci usually develop on an inner surface of the asoma, a layer called the hymenium or hymenial layer
Hymenium of an ascomycete showing asci with ascospores section thru the hymenial layer of Morela
The mycelium grows out from a germinating ascospore
Mycelium begins to reproduce asexually by forming conidia
Many conidia are produced Conidia are responsible for propagating
and disseminating the fungus
Ascomycete life cycle
Occurs on the same mycelium that produces conidia The formation of multinucleate gametangia called antheridia (male) and ascogonia (female) precedes sexual reproduction Male nuclei pass into the ascogonium via the trichogyne which is an outgrowth of the ascogonium Genetically different nuclei pair but do not fuse Ascogenous hyphae now begin to grow Compatible pairs of nuclei migrate and cell division occurs and creates dikaryotic cells- two compatible haploid nuclei
Spores produced by mitosis Spores called conidia (also called
mitospores) Formed by (1) fragmentation, (2)
fission, (3) budding, or (4) blastic development.
Chlamydospores - thick-walled resistant cells
Crozier- the apical cell of the ascogenous hypha which allows the paired nuclei to divide simultaneously
Compatible pair of nuclei fuse (karyogamy) to form a zygote
Zygote undergoes meiosis producing ascus with 8 nuclei
Haploid nuclei cut off to form ascospores Ascus as it matures becomes turgid, and
finally burst to release its ascospores
KeratinophylicKeratinophylic - live on hair, nails, dead - live on hair, nails, dead skin cells (protein keratin)skin cells (protein keratin)
Symptoms caused by enzymes that Symptoms caused by enzymes that irritate epidermal cellsirritate epidermal cells
Treatment may be systemic Treatment may be systemic (griseofulvum) or topical (azole (griseofulvum) or topical (azole antifungals, ciclopirox, others)antifungals, ciclopirox, others)