Fungi are eukaryotic organisms that lack chlorophyll and feed by absorbing nutrients from other living or dead organic matter. Their bodies are made of thread-like filaments called hyphae that branch and fuse to form a net-like structure called a mycelium. Hyphae have cell walls composed of chitin and glucans and contain vacuoles and nuclei. Fungi reproduce through both sexual and asexual means and play important roles in nature through symbiosis, decomposition, and as pathogens. They are also economically important for uses including food production, antibiotics, and bioremediation.

1. FUNGI- Structure and Composition
What are Fungi ?
from the Latin word ‘Fungus’ = Mushroom
Fungi are eukaryotic organisms that are achlorophyllous and heterotrophic
thallophytes.
 Body consists mostly of ‘thallus’ made up of ‘hyphae’ together constituting ‘mycelium’.
 The group consists of more than 5,100 genera with about 120,000 species including
yeasts, rusts, smuts, moulds, and mushrooms.

2. Characteristics and structure…
 Fungi are cosmopolitan in distribution- can occur in any habitat where life is
possible, e.g., fresh/marine water, terrestrial, air borne.
 Fungal body typically consists of branched and filamentous hyphae forming a
net-like structure- MYCELIUM.
 Hyphae are cylindrical, thread-like structures 2–10 µm in diameter and upto
several centimeters in length.
 Hyphae grow at their tips by emergence of new tips along existing hyphae-
called branching, also hyphal tips fork giving rise to two parallel-growing hyphae.
 Hyphae also sometimes fuse while in contact- hyphal fusion (anastomosis).

3.  These growth processes lead to the development of a “mycelium”- an
interconnected network of hyphae.
 Hyphae can be either septate or coenocytic. Septate hyphae are divided into
compartments separated by cross walls (septa) with each compartment
containing one or more nuclei; coenocytic hyphae are not compartmentalized.
Coenocytic hyphae are multinucleate super cells- single coordinated units.
 Septa have pores that allow cytoplasm, organelles, and sometimes nuclei to
pass through (e.g. the dolipore septum in the phylum Basidiomycota.

4.  The protoplast remains surrounded by a distinct cell wall. Main components
are ‘Chitin and Glucans’. Fungi- only organisms that combine these two
structural molecules in their cell wall.
 Fungal chitin (C8 H13 O5 N)n (long-chain polymer of N-acetylglucosamine) occur as
elongated variously oriented micro-fibrillar units, laid down in layers- maintaining the
structural rigidity of fungal cell walls. Glucan- polysaccharide derivative of D-glucose
linked by glycosidic bonds.
 The hyphae contain colorless and vacuolated cytoplasm. Besides, other cell
organelles and substances e.g., reserve foods occur in the cytoplasm. Fungi are
entirely devoid of chlorophyll, carotenoids are normally present.

6. /Apical body

7.  The higher fungi (Ascomycetes, Basidiomycetes, Deuteromycetes) are
immotile, but in lower fungi (Phycomycetes) the reproductive cells (gametes &
asexual zoospores) are uni- or biflagellate).
 Flagella are of two types: a) Whiplash flagella with smooth 9+2 organization,
and b) Tinsel flagella with two rows of numerous hair-like structures on their
surface- ‘Mastigonemes’- composed of glycoproteins.
Zoospore
Chytridiomycota
Zoospore
Oomycota
Zoospore
Hyphochytridiomycota
Zoospore
Oomycota

8.  Fungi are heterotrophic- don’t manufacture their own food (involve three
basic modes of nutrition as): Parasites, Saprophytes and Symbionts.
 Parasites- obtain nutrition from other living plants or animals.
 Saprophytes- obtain nutrition from dead decaying organic matter.
 Symbionts- grow on other living organisms and both are mutually benefited.
 Fungi reproduce by vegetative (fragmentation, fission and budding), asexual
(under favourable conditions through conidia or spores) and sexual (with three
distinct phases- Plasmogamy, Karyogamy and Meiosis) modes.
 Common with some plant and animal species, more than 70 fungal
species display bioluminescence.
 In 2017 an estimate suggested between 2.2 and 3.8 million species of Fungi.

9. Importance of Fungi for Human use…
 Mushroom farming and Mushroom gathering is a large blooming industry in
many countries functioning at local, regional, national and international scale.
 Production of antibiotics, vitamins, and anti-cancer and cholesterol-
lowering drugs.
 Very high significance in pharmaceutical industries and folk medicine
(e.g. Traditional Chinese medicine).
 Cultural foods- Baker’s yeast (Saccharomyces cerevisiae) – bread, pizza,
dumplings, alcoholic beverages, soy sauce, etc.
 Edible Mushrooms- Agaricus bisporus (button mushroom), straw mushrooms,
oyster mushrooms, black trumpets, and morels (Morchella sp).
 Pest control and Bioremediation- by suppressing the growth of harmfull plant
pathogens, by degrading insecticides, herbicides, pentachlorophenol, coal tars,
and heavy fuels and converting them into carbon dioxide, water, and basic
elements (e.g. white-rot fungi).