Fungi are eukaryotic organisms that cannot produce their own food and have important roles in nutrient cycling. They reproduce sexually and asexually and can have symbiotic relationships with plants and bacteria. Fungi can be terrestrial or aquatic and thrive in moist, warm conditions. They include saprophytes that obtain nutrients from dead organic matter, parasites that infect and feed on living hosts, and fungi that have mutualistic relationships with plants and animals. Fungi have complex cellular structures like hyphae, cell walls composed of chitin and glucans, nuclei, mitochondria, endoplasmic reticulum, and Golgi apparatus.

2. Defination of fungi
• Fungi are a kingdom of
usually multicellular eukaryotic organisms
that are heterotrophs (cannot make their own
food) and have important roles in nutrient
cycling in an ecosystem. Fungi reproduce
both sexually and asexually, and they also
have symbiotic associations with plants and
bacteria. However, they are also responsible
for some diseases in plants and animals. The
study of fungi is known as mycology.

3. Habitat of fungi
• Fungi are either terrestrial or aquatic, the latter
living in freshwater or marine environments.
• Large group,more then 1,00,000 species present in
the whole world.
• Ubiquitous , occur in almost every habitat where
organic matter is present .
• Donot require light for growth.
• Flourish well in moist, dark and in warm conditions.
• Some grow as parasites on other plants and
animals.

4. Aquatic habitat
• -They show unique
balance of external and
internal organic matter
supply.
• -Heterogenous in time
and space.
• -Coupling of aquactic
system to terrestial via
animals which are able to
export nutrients from
aquatic ecosystem.

5. Terrestail habitat
• They are member of
the group of
eukaryotic organisms
that includes
microorganisms such
as yeasts and molds,
as well as the more
familiar mushrooms.

6. Habit ( Mode of life)
•1) Saprophyte-
• Nutrients obtained from dead organic matter.
• Produce enzymes that degrade complex
polymers i.e. starch into simple polymers.
• Breakdown of polymers linked to hyphal
growth which provide penetration power.
• Hepls in recycling of major nutrients.
• They also produce mycotoxins on food.

7. Saprophytic fungi

8. 2) Parasites of plants
•Host specific fungus =biotropic
parasites,they feed on host cells without
killing them.
•If they attack badly on plant tissues then
they are called necrotrophic parasites .
• Parasitic fungi attack living organisms, penetrate
their outer defenses, invade them, and obtain
nourishment from living cytoplasm, thereby
causing disease and sometimes death of the host.

9. Parasitic fungus on trunk of tree

15. Life cycle of fungi

16. Asexual reproduction
• 1) Endospores-They are non-motile and bounded by cell
wall.eg.Rhizopus.They are produced endogenously by the division of
protoplasm within enlarged cell.Sporangiophore produced at end of a
special hypha.
• 2)Conidia- They produced nakedly(exogenously) by constrictions at
the end of special hyphal branches,called conidiophores
e.g,Aspergillus.
• 3)Oidia – The hyphae forming mycelium become divided by
transverse walls into large no.of short segments,which develop into
a new plant e.g.Mucor.

18. Methods of sexual reproduction
• 1)Planogametic copulation –Fusion of motile isogamous and
anisogamous planogametes.
• Gametangial contact- Many eggs within oogonium are fertilized by male
gametes through fertilization tube.
• 3)Gametangial copulation- In rhizopus etc.gametangia participate in
sexual reproduction.
• 4)Spermatogamy –Male spermatia are carried by insects,wind etc.to
female gametangia or to special receptive hypha.
• 5)Somatogamy- Involve nuclear fusion of somatic cells.

20. Ultrastructure of fungi
• 1) Cell wall-> The way in which fungus grows is determined by wall
components.
• Chitin, is a unique cell wall component of the fungi.The chitin is synthesized by the
membrane attached chitin synthase enzyme. Its zymogene is transported into the
cell membrane by the vesicles called chitosomes.
• The fungal cell walls contain polysaccharides mainly β(1,3) and β(1,6) glucans .
• Wall is interface b/w a fungus and environment protect from osmotic lysis.
• The zygomycota have mixture of chitin and chitosan and polymers of uronic acids.
• The oomycota have little chitin and have mixture of cellulose like beta-1,4-linked
glucan and other glucans.
• Wall composition is not fixed, it can change with change in stages of life cycle.
• Wall structure and composition reflects the functional need of fungus.
• Yeast cell have more mannan ,in the form of mannoproteins ,then hyphae .

21. Cell wall of fungi

22. Wall arehitecture of neurospora crassa
• In mature region of hyphae wall have 4 concentric zones,in
diff.layers.
• Outermost zone has amorphous glucans with beta1,3- and
1,6-linkage.
• Below this, network of glycoprotein embedded in protein
matrix.
• After some layers of protein ,innermost part of chitin
microfibrils embedded in protein.
• Wall is more strong and complex behind the extending
hyphal tip.

23. Neurospora crassa wall architecture

24. 2) Structure of hypha
• Hypha is tube with rigid wall which contain moving slug of
protoplasm.
• Hypha grow only at their tips ,where extension zone is present.
• Behind ext. zone, oldest region broken down by other organisms.
• Then protoplasm moves continuosly from older region towards tip to
supply materials for growth.
• Hyphal wall is thin at apex.
• The plasma mem. lies close to the wall.
• Hypha contain mem. Bound organelles i.e, nuclei,mitochondria etc.
• Apical compartment is densely protoplasmic with no vacuoles.
• Compartments behind hyphal tip may contain vacuoles,these are
small at first and larger in older compartments.

25. Structure of hypha

26. • 3) The nucleus
• The fungal chromosomes and
nuclei are relatively small, and
the chromosome number
generally is also low (4-8),
although much higher
chromosome numbers may
occur as well (e.g. 21
of Ustilago maydis (corn
smut)).
• Coenocytic hyphae and thalli
have many nuclei in each cell
or thallus.

27. • 4)endoplasmic recticulum:
• It is composed of a system of
membranes or microtubular
structures.
• 5)mitochondria:-
• The cytoplasm contains spherical
bodies known as mitochondria. The
inner membrane is infolded to form
the cristae .
• 6)Golgi apparatus :-
• It consist of three flattened sacs
surrounded by many bubble-like
structures.