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Presentation on theme: "Fungi."— Presentation transcript:

1 Fungi

2 Fungi Simple, aerobic organisms (such as mildews, molds, mushrooms, smuts, toadstools, and yeast) which unlike bacteria can grow in low moisture and low pH environments, Out of about 70,000 species of fungi some are edible but most are poisonous to humans. Their principal commercial uses include manufacture of food and alcoholic beverages, and antibiotics such as penicillin.

3 Characteristics of fungi
A. eukaryotic, non- vascular organisms B. reproduce by means of spores (conidia), usually wind-disseminated C. both sexual (meiotic) and asexual (mitotic) spores may be produced, depending on the species and conditions D. typically not motile, although a few (e.g. Chytrids) have a motile phase. E. like plants, may have a stable haploid & diploid states F. vegetative body may be unicellular (yeasts) or multicellular moulds composed of microscopic threads called hyphae.

4 G. cell walls composed of mostly of chitin and glucan.
H. Complex cytoplasm with internal organelles, microfilaments and microtubules fungi are heterotrophic ( “other feeding,” must feed on preformed organic material), not autotrophic ( “self feeding,” make their own food by photosynthesis).

5 J. Most fungi store their food as glycogen (like animals)
J. Most fungi store their food as glycogen (like animals). Plants store food as starch. K. Fungal cell membranes have a unique sterol, ergosterol, which replaces cholesterol found in mammalian cell membranes L. Tubule protein—production of a different type in microtubules formed during nuclear division. M. Most fungi have very small nuclei .

6 Morphology of fungi

7 Hyphae Hyphae are designed to increase the surface area of fungi and thus facilitate absorption May grow fast, up to 1 km per day, as they spread throughout a food source May be coenocytic, having no septa between cells, or septa may be present with pores through which cytoplasm can flow moving nutrients through out the fungus Parasitic fungi have modified hyphae called haustoria, which penetrate the host tissue but remain outside cell membrane

8 Hyphae

9 The Body of a Fungus Fungi exist mainly in the form of slender filaments (hyphae). long chains of cells joined end-to-end divided by cross-walls (septa) rarely form complete barrier cytoplasm freely streams in hyphae mycelium - mass of connected hyphae grows through and penetrates substrate

10 MYCELIUM Intertwined filamentous mass formed by hyphae, visible to the unaided eye Forms when environmental conditions are right Vegetative mycelium: Mycelial portion remaining INSIDE the substrate to obtain nutrition Reproductive mycelium: Mycelial portion extends into air ,responsible for SPORE reproduction 14

11 hypha mycelia

12 Structure Cell wall Plasma membrane Microtubules Nucleus

13 Fungal wall Shape of fungi Protect against osmotic lysis
It the wall contains pigments (melanin)  protect the cell against ultraviolet radiation or the lytic enzymes of other organisms It can have antigenic properties Function of cell wall;

14 Cell wall components Predominance of polysaccharides, lesser amounts of proteins and lipids. The major polysaccharides of cell wall matrix consist of glucans such as manans, chitosan, and galactans In yeasts, the cell-wall structure comprises polysaccharides (predominantly-glucans for rigidity), proteins mainly mannoproteins on the outermost layer for determining porosity), together with some lipid, chitin (e.g. in bud scar tissue) and inorganic phosphate material. Outside the cell wall in fungi, several extramural layers may exist, including fimbriae and capsules. Function of cell wall;

15 Plasma membrane The main role of the plasma membrane
To regulate the uptake and release of materials Integral membrane protein (chitin syntase, glucan syntase) Signal transduction Similar to mammalian plasma membrane, differing in having the nonpolar sterol ergosterol, rather than cholesterol regulates the passage of materials into and out of the cell by being selective permeable Several antifungal agents interfere with ergosterol synthesis (i.e., amphotericin B)

16 Functional components of an idealized fungal cell.
Organelle or cellular structure Function Cell envelope Comprising: the plasma membrane, which acts as a selectively permeable barrier for transport of hydrophilic molecules in and out of fungal cells; the periplasm, containing proteins and enzymes unable to permeate the cell wall; the cell wall, which provides protection, shape and is involved in cell–cell interactions, signal reception and specialized enzyme activities; fimbriae involved in sexual conjugation; capsules to protect cells from dehydration and immune cell attack. Nucleus Relatively small. Containing chromosomes (DNA–protein complexes) that pass genetic information to daughter cells at cell division and the nucleolus, which is the site of ribosomal RNA transcription and processing. Mitochondria Site of respiratory metabolism under aerobic conditions and,under anaerobic conditions, for fatty acid, sterol and amino acid metabolism.

17 Functional components of an idealized fungal cell.
Organelle or cellular structure Function Endoplasmic reticulum Ribosomes on the rough ER are the sites of protein biosynthesis. Golgi apparatus and vesicles Secretory system for import (endocytosis) and export (exocytosis) of proteins. Vacuole Intracellular reservoir (amino acids, polyphosphate, metal ions); proteolysis; protein trafficking; control of cellular pH. In filamentous fungi, tubular vacuoles transport materials bidirectionally along hyphae. Peroxisome Oxidative utilization of specific carbon and nitrogen sources (contain catalase, oxidases). Glyoxysomes contain enzymes of the glyoxylate cycle.

18 The study fungi is known as MYCOLOGY.
How do fungi live? Fungi feed on substances made by other living organisms. They digest their food before they absorb it by secreting acids and hydrolytic enzymes. Saprophytic fungi grow on dead matter. They help the decay process by breaking down dead material. Some species trap nematode worms in the soil as a source of nitrogen. Fungi that grow in living plants and animals may be parasitic and feed off their host athlete's foot and ringworm are examples of fungal infections in humans, or symbiotic, helping to supply nutrients that the host plant needs.

19 Classification of fungi

20 Kingdom Fungi – 5 Major Phyla
Phylum Zygomycota = the Bread Molds Rhizopus – black bread mold Oomycota = the Water Molds Water mold, potato blight, mildew Phylum Ascomycota = the Sac Fungi Yeast, morels, truffles Phylum Basidiomycota = the Club Fungi Mushrooms, puffballs, bracket fungi, rusts, smuts, toadstools Phylum Deuteromycota = the Fungi Imperfecti

21 Bread Mold – a Zygomycete Fungi

22 Note the cup shapes and orange peel colour
Cup Fungi – Ascomycete Fungi Note the cup shapes and orange peel colour

23 Bracket Fungi – Basidiomycete Fungi

24 Mushrooms – “Club Like” Fungi or Basidiomycete Fungi

25 IMPORTANCE OF FUNGI Fermentation industry
Remember fermentation is an anaerobic process Wine (yeast) Beer Bread Cheese (bacteria) Soy sauce (filamentous fungi (Aspergillus oryzae provides a low protein diet with amino acids, yeast & bacteria) soy beans & flour are held in a container for mold to grow—moldy beans are incubated for several months Sauerkraut Vinegar (yeast and bacteria) Yoghurt (Bacteria) 5

26 Drug manufacturing (usually their waste products are to our benefit)
Citric acid Ethanol (yeast) Antibiotic griseofulvin, penicillin Cortisone (Rhizopus) immunosuppressive agents (cyclosporine) SAPROPHYTE Degrade complex organic materials into simple ones, which become available for other organisms MYCORRHIZAE Fungi associated with plants Symbiosis Fungi help plant roots absorb minerals and water in the soil-serve as root extensions Fungi benefit by absorbing nutrients exuded by plant roots 6

27 Yeasts Yeasts are unicellular fungi that divide asexually by budding or fission, reproduce sexually by formation of spores and whose individual cell size can vary widely from 2 to 3 μm to 20–50 μm in length and 1–10 μm in width. Several yeasts are pigmented, and the following colours may be visualized in surface-grown colonies: cream (e.g. S. cerevisiae); white (e.g. Geotrichum candidum); black (e.g.Aureobasidium pullulans); pink (e.g. Phaffia rhodozyma); red (e.g. Rhodotorula rubra); orange (e.g. Rhodosporidium spp.); and yellow (e.g. Cryptococcus laurentii). The pigments of some yeasts have biotechnological uses, including astaxanthin from P. rhodozyma in aquacultural feed supplements for farmed salmon (that are unable to synthesize these natural pink compounds).


29 Chemical Requirements for Growth
Yeasts and fungi have relatively simple nutritional needs and most species would be able to survive quite well in aerobic conditions if supplied with glucose, ammonium salts, inorganic ions and a few growth factors. Element Common sources Cellular functions Carbon Sugars Structural element of fungal cells in combination with hydrogen, oxygen and nitrogen. Energy source Hydrogen Protons from acidic environments Transmembrane proton motive force vital for fungal nutrition. Intracellular acidic pH (around 5–6) necessary for fungal metabolism Oxygen Air, O2 Substrate for respiratory and other mixed-function oxidative enzymes. Essential for ergosterol and unsaturated fatty acid synthesis

30 Chemical Requirements for Growth (contd.)
Element Common sources Cellular functions Nitrogen NH4+ salts, urea, amino acids Structurally and functionally as organic amino nitrogen in proteins and enzymes Phosphorus Phosphates Energy transduction, nucleic acid and membrane structure Potassium K+ salts Ionic balance, enzyme activity Magnesium Mg2+ salts Enzyme activity, cell and organelle structure Sulfur Sulfates, methionine Sulfydryl amino acids and vitamins

31 Chemical Requirements for Growth (contd.)
Element Common sources Cellular functions Calcium Ca2+ salts Possible second messenger in signal transduction Copper Cupric salts Redox pigments Iron Ferric salts. Fe3+ is chelated by siderophores and released as Fe2+ within the cell Haem-proteins, cytochromes Manganese Mn2+ salts Enzyme activity Zinc Zn2+ salts Nickel Ni2+ salts Urease activity Molybdenum Na2MoO4 Nitrate metabolism, vitamin B12

32 Reproduction Yeasts, like all fungi, may have asexual and sexual reproductive cycles. The most common mode of vegetative growth in yeast is asexual reproduction by budding. Here, a small bud (also known as a bleb), or daughter cell, is formed on the parent cell. The nucleus of the parent cell splits into a daughter nucleus and migrates into the daughter cell. The bud continues to grow until it separates from the parent cell, forming a new cell. The daughter cell produced during the budding process is generally smaller than the mother cell. Some yeasts, including Schizosaccharomyces pombe, reproduce by fission instead of budding, thereby creating two identically sized daughter cells.

33 Reproduction( Cont..) In general, under high stress conditions like nutrient starvation, haploid cells will die under the same conditions, however, diploid cells can undergo sporulation, entering sexual reproduction (meiosis) and producing a variety of haploid spores, which can go on to mate (conjugate), reforming the diploid


35 Pathological Yeast Some species of yeast are opportunistic pathogens that can cause infection in people with compromised immune systems. Yeasts of the Candida genus are another group of opportunistic pathogens that causes oral and vaginal infections in humans, known as candidiasis. The pathogenic yeasts of candidiasis in probable descending order of virulence for humans are: C. albicans, C. tropicalis, C. stellatoidea, C. glabrata, C. krusei, C. parapsilosis, C. guilliermondii, C. viswanathii, C. lusitaniae

36 Oral candidiasis

37 Most common fungal infections
Many people have allergies triggered by mold. Fungal skin infections – skin, nails and hair Ringworm/ tineasis athlete’s foot Nail infection or peronychia

38 Most common fungal infections

39 Most common fungal infections

40 Economical benefits of Yeast
Production of Alcoholic Beverages such as wine, beers, Vodka etc. Widely use in the baking industry to produce bread and other bakery products Some yeasts can find potential application in the field of bioremediation. Production of nutritional supplements such as probiotic preparation widely used in genetics and cell biology (fundamental cellular processes such as the cell cycle, DNA replication, recombination, cell division, and metabolism) Yeast extract is the common name for various forms of processed yeast products that are used as food additives or flavours. Yeast is rich in vitamin been and protein. It is used in the productions of vitaminised food. It is also used in the production of riboflavin.

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