Fungus or Fungi

Characteristics of fungus
Classification of fungus
Structure of fungus
Advantages & Disadvantages of fungus

1. Fungus - Purvesh Mendapara

2. Definition Fungi are eukaryotic, saprophytic, parasitic nd unicellular or multicellular, devoid of chlorophyll microorganisms Fungi are among the most diverse organisms on earth, and are considered only second to the Insects in species diversity.

3. Characteristics Of Fungi

4. Nuclear status :- Eukaryotic & Multinucleate in nature , Haploid(N), Diploid(2N) Size :- Microscopic in nature Distribution :- Cosmopolitan Nutrition :- Absence of chlorophyll so Heterotrophic & Absorptive in nature Cell wall :- Well defined, typically chitinized but cellulosic in chromastian fungi Thallus :- On or in the substratum and unicellular or filamentous (mycelial), septate or non septate, typically non motile(with protoplasmic flow through the mycelium) but motile states may occur

5. Cell :- Most are multicellular but unicellular or single celled (yeasts) Sporocarps :- Microscopic & Macroscopic Food storage :- G enerally in the form of lipids and glycogen. Life cycle :- Simple to complex Reproduction :- Asexual, Sexual & Parasexual or Holocarpic & Eucarpic Habit :- Ubiquitous as saprobes, symbionts, parasites Movement :- Do not move itself Occurrence :- Occurs in air, water, soil and on plants & animals

6. Structure Of Fungi

7. Hyphae The vegetative bodies of most fungi is called thallus which constructed of tiny filaments called hypahe Tubular in shape Hyphae grow from their tips Branched (rarely unbranched) Multinucleate Hyphae Mycelium Thallus

8. Hyphae are divided into cells by internal cross walls called septa (singular:-septum) Due to septa there are two types of hyphae : 1)Septate hyphae 2) Aseptate hyphae

9. Mycelium Aggregate or mass of hyphae or extensive, feeding web of hyphae Mycelia are the ecologically active bodies of fungi Hardened mass of mycelium that generally serves as an overwintering stage is known as sclerotium Germinating spore Mycelium

10. Haustorium Outgrowth of intercellular hyphae of some parasite which enter the host cell is called haustorium Modified hyphae found in parasitic fungi Function: Absorb nutrients from host Some fungi even have hyphae adapted for preying on animals. Haustoria

11. Septa Uninterrupted mass running the length of the hyphae or the protoplasm may be intervals by cross walls called septa. Septa divide up hyphae into individual discrete cells or interconnected hyphal compartments. There can be various type of septa present in different fungi, they are complete septa, perforated septa, dolipore septa etc. It act as the first line of defence when part of a hypha is damage Also act as structural supports

12. Cell Wall Fungal cell wall contain 80-90% carbohydrates the remainder being proteins & lipids. Typically present, usually based on glucans, protiens and chitin, rarely on glucans and cellulose ( Oomycota ). Glucans and chitin are components of primary wall Proteins are components of secondary wall Functions of cell wall:- Protect against osmotic lysis Acts as a molecular sieve Binding site for enzymes

13. Cell structure Eukaryotic cell structure They have double membrane bound cell organelles like nucleus & mitochondria, tubular endoplasmic reticulum(ER), golgi bodies and the ribosomes. There are some differences from typical eukaryotic cells like the ribosomes lying free in the cytoplasm and not attached to the ER. The nuclei of some show unusual features. Lomasomes ( plasmalemasomes ) appear as particles or vesicles in pockets, formed between the cell wall and the plasmamembrane . Their function is not yet known. M any smaller vacuoles or a single large vacuole may be observed usually surrounded by the vacuolar membrane or tonoplast.

14. Spores Spore means any small propagative, reproductive or survival unit which separates from hyphae and gives rise to new individual Characteristics : Less water content Lack of vacuoles Slow metabolism Small & Light Formed : Directly on hyphae Inside sporangia By Fruiting bodies Asexual spores are Conidia, Zoospores, Sporangiospores ( Aplanospores ), Uredospores Sexual spores are Zygospores, Oospores, Chlamydospores, Basidiospores

15. Nutrition

16. Reproduction

17. Asexual reproduction Methods of asexual reproduction are, Fragmentation :- Detached fragment of hyphae in suitable conditions gives rise to a new individual (Ex. Cultivation in lab) Budding :- A soft zone appears on the cell wall which bulges out constricts and finally pinches off to form a daughter cell (Ex. Yeasts) Fission :- The cell divides in transverse plan into two cells and later formation of a cell wall inbetween ( Ex. Schizosaccharomyces ) Spores :- Spores are the most common method of asexual reproduction in fungi

18. Sexual reproduction Methods of sexual reproduction are, Planogametic copulation :- Male & Female gametes are motile and conjugate outside the gamentangium Gametangial contact :- Male gametic nucleus migrates into the oogonium either through a pore formed at the oint pf contact or through a fertilization tube developed by antheridium Gametangial copulation :- The entire contents of the two gametangia fuse and become one Spermatization :- Non motile spore like male structure empties its content into a receptive female structure during plasmogamy Somatogamy :- Fusion between undifferentiated vegetative cells or spores is called somatic copulation or somatogamy

19. Classification of fungi

20. Domain Eukarya

21. Chytridiomycota – “ chytrids ” Chytrid derived from ‘ chytridion ’ meaning ‘little pot’ Smallest & Simplest fungi Most primitive fungi Distinguishing feature produce motile & whiplash flagellum zoospores which are ideal for dispersal in the aquatic environments mostly freshwater and moist soils where they are commonly found They include both free living forms that degrade organic material and parasites of animals & plants Ex. Synchytrium endobioticum

22. Zygomycota – “zygote fungi” Main characteristics is sexual reproduction by zygospores . It is fusion of two gametangia Fungi reproduces asexually by aplanospores or conidia sporangiospores Cell wall made from chitosan chitin Hyphae have no cross walls Grow rapidly Commonly found in soil and on decaying plant material (decomposes) Divided into 2 classes: Zygomycetes & Trichomycetes Ex. Bread molds

23. Ascomycota – “sac fungi” Largest phylum of fungi having 75% of all known fungi The ascus & two layered cell wall are the diagnostic features of Ascomycota. The wall has a thin electron dense outer layer & relatively thick electron transparent inner layer. Septate hyphae structure Presence of dikaryophase in lifecycle Absent of flagellated structures Asexual reproduction by conidia Ascomycetes are ecologically important in freshwater, marine, terrestrial habitats because they degrade many chemically stable organic compounds like lignin, cellulose Decomposers, pathogens, and found in most lichens Ex. Cup fungi, morels, truffles, Brewer’s yeast( Saccharomyces cerevisiae), ergot disease

24. Glomeromycota That phylum have critical ecological importance because they are mycorrhizal symbionts of vascular plants. Mycorrhizal fungi form important associations with the roots of almost all herbaceous plants & tropical trees. Obligate symbiosis Formation of arbuscules in plant root cells Coenocytic hyphae structure present Large multinucleate spores with layered walls AM fungi form asexual spores called glomerospores which serves as the only means of reproduction. The spores are very large (80-400 µm) No evidence of sexual reproduction Ex. Mycorrhizae

25. Spore Hyphae

26. Endo Mycorrhizae Ectomycorrhizae

27. Oomycota - “egg fungi” Also known as “Pseudo fungi” Cell wall made up of glucan -cellulose (rarely with minute amount of chitin) Sterol in oomycota is fucosterol not ergosterol which found in true fungi Diploid somatic phase Thick walled oospores Biflagellate zoospores with one tinsel type flagellum and other whiplash type Mycolaminarin as storage product The tinsel type flagellum and mycolaminarin are key characters of these fungi that place them in Chromista Oomycota radically differ from ‘true fungi’ in lysine biosynthetic pathway. Ex. Pythium, Phytophthora, Albugo

28. Basidiomycota – “club fungi” Contain 30000 species which is 37% of true fungi These recognized as the highest evolved group of fungi Most conspicuous fungi in environment The most important feature is production of basidiospores which are sexual spores. But being internal the basidiospores externally on the basidium Long-lived dikaryotic mycelia Other features included : The highly developed dikaryophase of the thallus The formation of clamp connection on the dikaryotic hyphae The presence of the dolipore septa in some and Double layered cell wall present Ex. Mushrooms, shelf & bracket fungi, puffballs, rusts & smuts disease

29. Symbiotic association

30. Mutualism :- Two organisms living together, both benefit (Ex. Lichen, Mycorrhizae) Parasitism :- In which one of the two partners lives at the expense of the other means one organism benefits, the other is harmed or killed slowly (Ex. Insects are infected with fungus) Saprobes :- O btain nutrients from nonliving organic material or from the remains and byproducts of organisms (Ex. Decomposers fungi)

31. Advantages of fungi

32. Food production (Edible mushroom) Biological control ( Trichoderma viride , Beauveria bassiana ) Enzyme activity (Cheese ripening) Metabolites (Plant growth hormones) Biotransformation (Yeast formation) Produced antibiotics (Penicillium notatum) Produced some organic acids (citric acid, gluconic acid, fumaric acid) Produced some industrial enzyme ( invertase , pectinase, proteases)

33. Disadvantages of fungi

34. Spoilage (grains, fruits, vegetables) Allergic responses Mycotoxins (Aflatoxins, Ochratoxin) Fungal infection in animal & human (ringworm) Plant diseases (rust, smut, powdery mildew disease)

35. References An introduction to fungi. H C Dube Prescott’s microbiology. Willey, Sherwood, Woolverton Brock biology of microorganisms. T.Madigan