CLASSIFICATION AND CHARACTERISTICS OF FUNGI

Characteristics of fungi

Branch which deals with the studies of fungi is called mycology. Mode of nutrition in the fungi is heterotrophic. Most of them are saprophytes, while others maybe parasites. Other than yeast which is unicellular, most of the fungi are multicellular.

• Hyphae: Thread like structure in fungi.
• Mycelium: Loosely organized mass of hyphae.
• Thallus: body of fungus consists of mycelium.
• Septa: Hyphal cells are separated by cross-walls called septa

Cell wall of fungi is made up of chitin. All fungi possess lysosomal enzyme which helps the fungi in attacking the host cells and in digesting the decayed matter. Some fungi along with yeast have plasmid this is helpful in cloning the foreign genes. This property found useful in the genetic engineering.

Single hyphal cell of yeast may have 1-2 nuclie. Each hyphal cell is separated with the help of septa. Flow of nutrition form one hyphal cell to other is made possible through the hole present in the septa.

Reproduction in fungi may be sexual, asexual or both. Few fungi are only able to undergo asexual reproduction. Asexual reproduction is done through mitotic divisions in cell, for e.g., budding in yeast. Sexual reproduction is done though plasmogamy, karyogamy and formation of dikaryotes in some organisms.

Classification of fungi

Classification of fungi is based upon the nature of sexual stages in their life cycle. According to this, fungi can be classified into following classes:

Zygomycota

• Also known as bread moulds
• Their hyphae lacks septa
• They produce spores which have two strains, plus and minus strain.
• Plus and minus strain fuse together to form a zygote which is enclosed in zygospore.
• Zygospore is thick-walled and a resistant structure which can also produce spores.
• In the hyphal spores genetic information comes from single strain, whereas, in zygospore it comes from two strains.
• Example: Rhizopus

Ascomycota

• Also known as sac fungi.
• Their hyphae have a septa with a central pore.
• During sexual reproduction, they produce a sac like structure known as ascus.
• During asexual reproduction, they produce conidia present at the end of the hyphae.
• Sexual reproduction includes formation of antheridium or ascogonium and ascospores.
• Examples: Neurospora, Penicillium notatum, P. roquefortii, P. camemberti, Candida albicans, Trichophyton, Aspergillus, Blastomyces, Histoplasma

Basidomycota

• Also known as club fungi.
• In these, hyphae came together to form mycelia.
• Forms club-shaped sexual structure called basidia.
• Sexual spores are called basidiospores.
• Dikaryotic mycelium forms when mycelia unites.
• Examples: Amanita, Claviceps, Cryptococcus.

Deuteromycota

• Also known as fungi imperfecti.
• There is no sexual stage present in their life cycle.
• Some soil organisms and various human pathogens are from this class of fungi.

MCQs

1. Cell wall of fungi is made up of?

a. Cellulose

b. Hemicellulose

c. Chitin

d. Lignin

2. Mode of reproduction is fungi is?

a. Sexual

b. Asexual

c. Both a . and b.

d. None of the above

3. Zygomycota are also known as?

a. Bread moulds

b. Sac fungi

c. Club fungi

d. Fungi imperfecti

4. No sexual stage is found in which class of fungi?

a. Ascomycota

b. Basidiomycota

c. Deuteromycota

d. Zygomycota

5. Which of the following statement is INCORRECT related with the zygomycota class of fungi?

a. They produce plus and minus strains of spores

b. They have a septa having a central pore in it

c. Rhizopus is the member of this class

d. Zygospore so formed is thick walled and resistance structure

6. Match the following members of fungi with their correct class-

a. i-A, ii-C, iii-B

b. i-A, ii-D, iii-D

c. i-B, ii-C, iii-A

d. i-B, ii-D, iii-C

7. Match the following structure of fungi with their correct description-

a. i-A, ii-C, iii-B, iv-D

b. i-A, ii-D, iii-D, iv-D

c. i-B, ii-C, iii-A, iv-D

d. i-B, ii-D, iii-C, iv-A

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ANSWERS

1-c

2-c

3-a

4-c

5-b

6-a

7-c

REFERENCES