Ascomycetes

There are many members in kingdom Fungi which shows few common characteristics like presence of long, tubular structures called as hyphae.

They also possess certain differences that are used to classify them into four classes which are Ascomycetes, Phycomycetes, Basidiomycetes and Deuteromycetes.

Let us now see the characteristics of Ascomycetes that makes it different from the other fungi

Ascomycetes are haploid fungi made up of septate, branched hyphae and shows presence of septal pores.

The most distinctive characteristic of ascomycetes is formation of sac-like structure called as ascus (borne on fruiting bodies called as ascocarps).

The asci is formed by fusion of two hyphae of opposite mating types ( male and female).

The fusion can take place by gametangial contact, gametangial copulation, spermatisation or somatogamy .

After the fusion of hyphae, haploid nuclei in young ascus fuse to form a diploid nucleus of zygote.

Resulting zygote then undergoes meiosis resulting in formation of 8 ascospores which are released after rupture of asci.

Formation of ascospores in asci is important part of sexual reproduction in this class of fungi.

While asexual reproduction takes place by oidia, chlamydospores and conidia.

Yeast which is a member of Ascomycetes, shows vegetative reproduction like budding, binary fission and fragmentation.

Yeast are unicellular, saprophytic and grows on sugary medium like sugarcane juices, fruits etc.

Some of the yeast shows ascus formation and they are known as true yeasts.

Some others like Candida, Mycoderma do not show ascus formation and they are known as false yeasts.

Budding, fission and halobial are the three types of yeasts based on their mode of reproduction.

Saccharomyces is an example of budding yeast and schizosaccharomyces is an example of fission yeast.

Sometimes in budding yeasts, daughter cells also start forming buds before getting separated from mother cell.

This results in formation of branched or unbranched chains of cells known as pseudomycelium.

Halobial yeasts like Saccharomycodes shows both budding and fission.

Halobial yeasts are helpful to us as they are used in bread making, manufacturing of wine, alcohol and glycerol by fermentation.

Some yeasts are harmful too as they spoil food and causes various diseases of brain, skin and lungs.

Apart from yeasts, there are many other important examples of Ascomycetes too.

Let us see the characteristics of some members from Ascomycetes.

Aspergillus is useful in production of citric acid, oxalic acid, gluconic acid, gallic acid, glycerol, enzymes, antibiotics and vitamins.

But some species of Aspergillus are harmful as they cause rot disease (in plants) aspergillosis (in animals) and produces carcinogenic aflatoxins.

Penicillium (also called as green and blue mould) is used for the production of organic acids and roquefort, camembert varieties of cheese.

Penicillium grisefulum produces antifungal drug, griseofulvin while wonder drug penicillin is produced by Penicillium notatum or crysogenus.

Claviceps purpura causes ergot in cereals by forming sclerotia and its consumption causes ergotism.

Sclerotia contains many alkaloids like lysergic acid which is used in treatment of migraine and enlarged prostate gland.

A well known-hallucinogen lysergic acid diethylamide (LSD) is obtained by fermentation activity of Claviceps paspali.

Neurospora (also known as pink bread mould) has been extensively used in genetic studies.

Morels, gucci or sponge mushrooms (Morchella) and truffles (Tuber uncinatum and T. aestivum) are examples of edible fungi.

Erysyphe graminis causes powdery mildew of cereals.

Erysyphe polygoni causes powdery mildew of grams and powdery mildew of cucumbers is caused by Erysyphe cichoracearum.

Revision

Ascomycetes is class of fungi that is characterised by formation of ascospores in sac like asci.

Yeast is an important example of this class and it's helpful in bread making, manufacturing of alcohol, glycerol etc. Yeast is an important example of this class and it's helpful in bread making, manufacturing of alcohol, glycerol etc.

Other important examples are Aspergillus and Penicillium which are used to obtain drugs, organic acids as well as few species of them causes diseases.

The End