Kingdom Fungi Introduction Prof Khaled AbuElteen Objectives Introduction

Kingdom Fungi Introduction Prof. Khaled Abu-Elteen

Objectives Introduction of fungi n Biology of fungi n n n Physiology of fungi n n Cell structure, growth and development Nutrition, Temp, UV light, and water Classification of fungi

Some terms n mycology n n mycologists n n scientists who study fungi mycotoxicology n n study of fungi study of fungal toxins and their effects mycoses n diseases caused by fungi

FUNGI 100, 000 species 100 human pathogens, fungi associated diseases are rising, due to nosocomial infections and in immunocompromised patients (ie. HIV, diabetes, transplant folks) Aspergillosis, Blastomycosis—pulmonary infections and dissemination may be involved 5, 000 plant pathogens=$1 billion/yr

Fungal Characteristics n n n n Eukaryotic Multicellular Heterotrophic Absorb nutrients - may be saprobes (absorb from dead material), parasites, or mutualistic symbionts (with algae make lichen). Secrete powerful hydrolytic enzymes Cell walls contain chitin, an amino sugar polysaccharide also found in arthropod exoskeletons Lack flagella

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. G. cell walls composed of mostly of chitin and glucan. H. Complex cytoplasm with internal organelles, microfilaments and microtubules

H. fungi are heterotrophic ( “other feeding, ” must feed on preformed organic material), not autotrophic ( “self feeding, ” make their own food by photosynthesis). - Unlike animals (also heterotrophic), which ingest then digest, fungi digest then ingest. -Fungi produce exoenzymes to accomplish this I. 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, with little repetitive DNA. N. Mitosis is generally accomplished without dissolution of the nuclear envelope

Introduction of fungi Eukaryotic, Heterotrophic (chemoheterotrophic) microorganism n No chlorophyll, non-motile n Thread of cells (hyphae), transverse cell walls (septate), hyphal anastomosis n Storage compound; glycogen n

Molds n filamentous fungi n hyphae (s. , hypha) n n n the filaments of a mold may be coenocytic (no cross walls) or have septa (cross walls) mycelium (pl. mycelia) n bundles or tangled masses of hyphae

Yeasts unicellular fungi n reproduce asexually, often by budding n reproduce sexually by formation of spores n

Hyphae n n 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

Hyphae

Hyphae Pores Septa Coenocytic

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

MYCELIUM n n 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

Introduction of fungi Other characteristics of fungi n the ability to synthesize lysine by the -amino adipic acid pathway (AAA-pathway) n possession of a chitinous cell wall n plasma membranes containing the sterol ergosterol n and microtubules composed of tubulin.

Structure n n Cell wall Plasma membrane Microtubules Nucleus

Fungal wall n n 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

Cell wall components n Predominance of polysaccharides, lesser amounts of proteins and lipids

Table 1 Major polysaccharide components of fungal walls Division Fibrillar components Matrix components Chytridiomycota Chitin, glucan Glucan Zygomycota Chitin, chitosan Polyglucoronic acid, glucuronomannoproteins Ascomycota/ Chitin, (1, 3)- (1, 6)deuteromycota glucans Basidiomycota Chitin, (1, 3)- (1, 6)glucans -(1, 3)-Glucan, galactomannoproteins , ,

Cell wall components n The major polysaccharides of cell wall matrix consist of glucans such as manans, chitosan, and galactans n n n Glucan refers to a group of D-glucose polymers having glycosidic bonds Insoluble -glucans are apparently amorphous in cell wall Mannans, galactomannans, rhamnomannans are responsible for the immunologic response to the medically important yeasts and molds

Cell Wall Structure In Fungi

Cell wall components n Consisting of chitinous microfibrils embedded in the matrix of small polysaccharides, proteins, lipids, inorganic salts, and pigments n n n Chitin is a ( 1 -4)-linked polymer of N-acetyl-Dglucosamine (Glc. NAc) Produced in cytosol (from UDP Glc. NAc into chains of chitin by chitin synthetase) The chitin microfibrils are transported to the plasmalemma and subsequently integrated into the new cell wall

Cell wall components n n In addition to chitin, glucan, and mannan, cell walls may contain lipid, protein, chitosan, acid phosphatase, amylase, protease, melanin, and inorganic ions (phosphorus, calcium, and magnesium) The outer cell wall of dermatophytes contains glycopeptides that may evoke both immediate and delayed cutaneous hypersensitivity

Plasma membrane n The main role of the plasma membrane n n n To regulate the uptake and release of materials Integral membrane protein (chitin syntase, glucan syntase) Signal transduction

Plasma membrane Similar to mammalian plasma membrane, differing in having the nonpolar sterol ergosterol, rather than cholesterol n regulates the passage of materials into and out of the cell by being selective permeable n Several antifungal agents interfere with ergosterol synthesis (i. e. , amphotericin B) n

Microtubules Composed of the protein tubulin, which consists of a dimer composed of two protein subunits. n Microtubules are long, hollow cylinders ~ 25 nm in diameter n Involved in the movement of organelles, chromosomes, nuclei, and Golgi vesicle containing cell wall precursor n

Microtubules Assist in the movement of chromosomes during mitosis and meiosis n the destruction of cytoplasmic microtubules interferes with the transport of secretory materials to the cell periphery, which may inhibit cell wall synthesis n

Nucleus n n n The nucleus is bounded by a double nuclear envelope and contains chromatin and a nucleolus Fungal nuclei are variable in size, shape, and number The number of chromosomes varies with the particular fungus n n S. cerevisiae ; 18 (n) T. mentagophytes ; 4 (n)

The growth of hyphae n n n Apical extension Balance between wall synthesis and wall lysis The apical vesicles are produced from Golgi bodies and then transported to the tip Spitzenkörper (apical body)

n The vesicles fuse with the plasma membrane at the tip, and release their contents. n n enzymes involved in wall synthesis, (chitin syntase, glucan synthase) enzymes involved in wall lysis, enzyme activators, some preformed wall polymers such as mannoproteins

Physiology Aeration n Nutrition n Water n Temperature n Hydrogen ion n Light n

Aeration n The fungi include species that are obligately aerobic (eg. most Zygomycota), obligately anaerobic (eg. rumen fungi( Organisms can obtain energy by oxidative (respiratory) metabolism or by fermentation O 2 is used for oxidative metabolism to generate energy. However it is essential for biosynthesis of sterols, unsaturated fatty acids and some vitamins

Table 2 Energy metabolism in relation to O 2 requirements Obligately oxidative. Obligate aerobes. Exp. Rhodotorula Facultatively fermentative. Energy can be obtained by oxidative and fermentative processed such fungi are likely to be faculative anaerobes. Oxidative metabolism, provides much more energy than fermentative, so higher yields can occur under aerobic conditions. Exp. Mucor, Saccharomyces Obiligately fermentative. Oxygen is not needed for energy production , may be either harmless or toxic. Exp. Blastocladia, Neocallimastix

Diagrammatic representation of the mixed-acid fermentation of the rumen chytrid Neocallimastix. Part of the fermentation occurs in the cytosol and hydrogenosome Hydrogenosome: functionally equivalent to the mitochondria of aerobic organisms

The nutrient requirement of fungi n Carbon needs for the synthesis of carbohydrates, lipids, nucleic acids, and proteins. n n Simple sugars, polysaccharides, citric acid, glycerol Nitrogen for synthesis of amino acids for proteins, purines and pyrimidines for nucleic acids, glucosamine for chitin, and various vitamins n Amino acid, ammonium, nitrate

Nutrition n n C/N ratio (20: 1) Other elements n n n P : energy-rich compound metabolism, phospholipid in lipid bilayer K : coenzyme Mg : concer with sporulation S : protein component Trace elements n Fe, Cu, Mn, and Zn

Nutrition

Czapek-Dox medium widely used for the culture of fungi Mineral base: C and energy source: N source: Water: If a solid medium is required: KH 2 PO 4 Mg. SO 4. 7 H 2 O KCl Fe. SO 4. 7 H 2 O Sucrose (Glu, starch) Na. NO 3 Agar 1 g 0. 5 g 0. 01 g 30 g 2 g 1 litre 20 g

Water availability n n n Most fungi require very high water availability (relative humidity), and rapidly dry out or senescence in dry conditions. Water activity (aw) = ps/pw (pure water = 1) DNA is denatured at aw = 0. 55 n n Osmophiles 0. 85, Xerophiles 0. 80, Halophiles 0. 75 The xerotolerant fungi can grow slowly, at water activity of 0. 64.

Temperature

Hydrogen ion Opt. p. H 5. 0 -7. 0 n Acid-tolerant (p. H 2. 0) Aspergillus, Penicillium, Fusarium, yeast in stomach of animals n Strongly alkaline environment (p. H 10 -11) F. oxysporum, P. variabile n

Light Influence on fungal growth in specific cases n light does not play a major part in growth and metabolism of fungi n A common metabolic effect of light is the induction of carotenoid biosynthesis n

Morphology Yeast n n Unicellular, round or oval, size 8 -15 x 3 -5 µm Conidiogenesis (budding, binary fission, sexual spores) Budding yeasts Binary fission

Morphology Mold n n Multicellular, hyphae, septate & nonseptate, hyaline & dematiaceous, diameter 4 -20 µm Sexual and asexual reproduction Hyaline septate hyphae Dematiaceous septate hyphae Hyaline aseptate hyphae

Morphology Dimorphic fungi (thermally dimorphic fungi) Environment/Routine culture media (SDA) 25 -300 C ---Mold form Sporothrix schenckii Tissue/Enriched media (BHI) 35 -370 C---Yeast form

Morphology

For example, the dimorphic fungus Blastomyces dermatitidis n Anamorph : hyphae, conidia at 250 C and budding yeast cell at 370 C n n The name B. dermatitidis summarizes these two anamorphs Teleomorph : sexual fruiting body, called a gymnothecium, containing ascospores n The name that is used for this sexual form or teleomorph is Ajellomyces dermatitidis

Sexual reproduction Gametes or gametic nuclei (n( n (haploid( Meiosis n (monokaryon( Plasmogamy (cell fusion( n+n (dikaryon( (2 n (diploid Zygote (2 n( Karyogamy (nuclear fusion(

Division Ascomycota n n Common name: Sac fungi Sexual reproduction: ascospore in ascus n n Asci may form in fruiting body called an ascocarp Gymnothecium, Cleistothecium, Perithecium, Apothecium n Asexual reproduction: conidia, arthospore, budding septate hyphae or yeast n Eurotium (Aspergillus) , . Arthroderma (Trichophyton) n

Life cycle of ascomycetes Arthospore

Cleistothecium Ascocarp Gymnothecium Perithecium Apothecium

Life cycle of the yeast Saccharomyces cerevisiae a c b

Division Basidiomycota Common name: Club fungi, mushroom n Sexual reproduction: basidiospore n Asexual reproduction: budding n hyphae with dolipore septum or yeast n clamp connection n Mushroom: basidiocarp, fruiting body n n Filobasidiella neoformans (no basidiocarp) or Crytococcus neoformans

Clamp connection

Life cycle of basidiomycetes

Amanita phalloides

Division: Zygomycota Common name: Bread molds n Sexual reproduction: Zygospore n n Mating type +, mating type - Asexual reproduction: Sporangiospore, sporangium n coenocytic hyphae (aseptate hyphae) n Rhizopus sp. , Mucor sp. , Asidia sp. n

Life cycle of Rhizopus stolonifer

Division: Chytidiomycota Common name: Water molds n Sexual reproduction: Oospore n Asexual reproduction: Zoospore, zoosporangium, flagella n aseptate hyphae n Phythium insidiosum n

Deuteromycota Common name: Imperfect fungi n have no known sexual state in life cycle n Asexual reproduction : conidia (blastic, thallic( n septate hyphae or yeast n Human pathogenic fungi: dermatophytes, dimorphic fungi n

Conidiogenesis Blastic: the conidium originate from a narrow portion of the region which swells before being cut off by a septum Phialophora Cladosporium Curvularia Penicillium Scopulariopsis

Blastic conidiogenesis Acropetal conidia n Sympodia condia n Poroconidia n Phialoconidia n Anneloconidia n

Conidiogenesis Thallic: the conidium arise from a broad zone of the region and septa laid down before the conidium swells Candida albicans Geotrichum Microsporum Trichophyton

Thallic conidiogenesis Arthoconidia n Thallic solitary conidia n Chlamydoconidia (chlamydosprore ( n