Ascomycetes ppt for bsc 3rd year st.pptx

fungi

1. Ascomycetes: Phylum Ascomycota

2. Ascomycetes are organisms that belong to the phylum Ascomycota. The phylum Ascomycota is the largest in the kingdom of fungus, with about 64000 species. They are part of the Dikarya sub-kingdom. Today, in this article we are going to learn about Ascomycetes, their life cycle, their importance, and more.

3. The living habitat and the feeding habits of the ascomycetes are very diverse, some of them are saprophytes and the others are pathogens causing various diseases in plants and animals. Some of the ascomycetes are edible like mushrooms and some of them live in a symbiotic association like lichens and mycorrhiza . Some of the ascomycetes examples are yeast, powdery mildews, cup fungi, morels, truffles, Neurospora, Aspergillus, Cladonia , Penicillium, Candida, Claviceps, etc.  

4. The reproductive structure of the ascomycetes is known as ascus or asci . Most of the ascomycetes are terrestrial, parasitic or coprophilous. It might be unicellular or multicellular fungi. The mycelium of the ascomycetes is made up of septate or branched hyphae and the cell wall is made up of chitin or ꞵ-glucans. Ascomycetes have cytoplasmic continuity due to septal pores. In ascomycetes , asexual reproduction is by the formation of conidia exogenously on conidiophores and Sexual reproduction is by conjugation between two gametangia . They can be either homothallic or heterothallic. In ascomycetes , the fruiting body is called ascocarp and there are mainly four types of ascocarps . Ascomycetes examples of ascospores are cleistothecium , perithecium, apothecium, and ascostroma . Ascospores are produced endogenously in ascii .  General Characteristics of Ascomycetes.

5. Economic Importance of Ascomycetes   1 . They are one of the biggest groups of fungi having diverse habitats. 2. Many useful products are derived from them like foods, medicines, and some chemical products.  3. Many food industries depend on yeast for fermentation like brewing, bread and cheese making.  4. They are used to make antibiotics like penicillin, which is derived from  Penicillium chrysogenum . 5. Ascomycetes produce many organic acids and enzymes like citric acid, gluconic acid, amylases, proteases, etc. 6. Ciclosporin derived from the fungus Tolypocladium niveum is used to transplant organs and treat autoimmune diseases. It is used as an immunosuppressant. 7. It is used to prepare different types of cheese using different penicillium species like camembert, brie, and Roquefort. 8. Ascomycetes like Claviceps purpurea (Ergot) are used as medicine to stop excessive bleeding during menstrual periods and to speed up labour. 9. They are one of the delicacies like morels, truffles and lobster mushrooms. 10. Aspergillus is used to prepare soya sauce and also other Asian alcoholic beverages.  11.Some of the ascomycetes are widely used to study genetics Neurospora , Saccharomyces, etc.

6. Ascomycetes Group of fungi characterized by their production of sexual spores in a sac-like structure called an ascus.

7. “ Cup fungus ”

8. Types of Ascomycete s yeast powdery mildew cup fungi – many of these produce spores suited for airborne dispersion.

9. The Ascomycota Non motile Form ascospores Internally in Asci Most are blue-green, red and brown molds that cause food spoilage Penicillin

10. Ascomycetes Eyelash cup, Scutellinia scutellata

11. Ascomycetes can cause plant disease Brown rot of stone fruits ( Monilinia fructicola ) chestnut blight ( Cryphonectria parasitica )

12. Dutch elm disease ( Ophiostoma ulmi )

13. Beneficial Ascomycete Many Yeast are also ascomycetes Edible Morels and truffles

14. Edible black truffle, Tuber melanosporum spore-bearing structure is produced below ground mainly on oaks and hazelnuts

15. Edible Ascomycete

16. Ascomycetes growth 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

17. Life cycle of an Ascomycete 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”

18. Conidia- the characteristic asexual spores of ascomycetes shows the stages in the formation of conidia which infects the velvetbean caterpillar

19. TEM of Various stages of developments of conidida

20. Ascomycetes spore development vs. Zygomycetes spore development Unlike zygomycetes which produce spores internally within a sporangium, ascomycetes produce their asexual spores externally as conidia.

21. Sexual reproduction in Ascomycetes 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.

22. Maturing ascospores in Asci of Ascodesmis nigricans

23. Enclosed asci and ascospores of Ascoma called a cleistrothecium

24. An ascoma of Coniochaeta showing the enclosed asci and ascospores Perithecium- fruiting body contains ascospores

25. Xylaria fungus “Dead mans fingers” Perithecium with ascospores Finger Xsec

26. Hymenial layer Asci usually develop on an inner surface of the asoma, a layer called the hymenium or hymenial layer

27. Hymenium of an ascomycete showing asci with ascospores section thru the hymenial layer of Morela

28. Life cycle of Ascomycete 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

29. Ascomycete life cycle

30. Sexual Reproduction 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

31. 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