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)