Fungi

Microorganism : Fungi, Classification, structure , general characteristics and morphology related to food

1. FUNGI

2. F ive-kingdom system All life on earth is divided into five kingdoms: Plants Animals Fungi Protozoa Bacteria

3. FUNGI Fungi are eukaryotic microorganisms Two major groups of organisms make up the fungi. The multicellular filamentous fungi - molds The unicellular fungi - yeasts. Study of fungi – mycology Study of fungal diseases - mycoses

4. All molds are fungi but all fungi are not molds-- yeasts are fungi but they are unicellular and produce no aerial mycelium molds filamentous fungi that produce aerial mycelium  

5. The Kingdom of the Fungae Myceteae Great variety and complexity Approximately 100,000 species Majority are unicellular or colonial

6. The Kingdom of the Fungae Can be divided into three groups: Yeasts Molds Macroscopic Fungi

7. The Kingdom of the Fungae Can be divided into three groups: Molds Long, threadlike cells Filamentous arrangement (hyphae) Some are dimorphic (yeast-like and filamentous forms exist)

8. The Kingdom of the Fungae Macroscopic fungi Mushrooms, toad stools Bracket fungi Stink horns

9. What is a Fungus? To be considered a fungus, an organism M ust be eukaryotic Possess cell walls G row by extending filamentous cells called hyphae, or by budding O btain nutrients by releasing digestive enzymes into the environment to break down organic molecules, which are then absorbed H ave no chlorophyll . cell walls have chitin.

10. Different forms of Fungi mushrooms rusts molds truffles yeast

11. General Characterstics of Fungi

12. General Characterstics Molds consist –long, branched, thread like filaments of cells called hyphae . The total hyphal mass of a fungus is called as mycelium. The hyphae may be septate or aseptate ( coenocytic ) Many fungi are dimorphic in nature and change from a yeast form to a mold form. They consist typical eukaryotic nuclei and membrane bound organelles. The ribosomes are of 80s type. Most of the fungi are saprophyte s and secure nutrients from dead organic material. They grow best at optimum p H of 5.5 and optimum temperature of 20-35 C. Fungi are aerobic in nature. Some yeasts are facultatively anaerobic and carry out fermentation.

13. General Characterstics Majority of fungi are terrestrial. A few are fresh water or marine. Some are parasitic and some are symbiotic. Many are pathogenic and cause several diseases. They are the important decomposers and breakdown the organic matter. They lack chlorophyll and cannot carryout photosynthesis. They range in size from single-celled microscopic yeast to multicellular molds and macroscopic puff balls and mushrooms. They may be unicellular (yeasts) or multicellular and filamentory ( molds).

14. General Characterstics Their primary storage material is glycogen which is a polysaccharide. They reproduce asexually, sexually or by both methods. The asexual reproduction occurs by the production of specific types of spores such as arthrospores , chlamydospores , sporangiospores , conidiospores , zoospores and blastospores . Some fungi exhibit binary fission type of reproduction. Sexual reproduction involves the union of two compatible nuclei or sex organs or sex cells. They produce sexual spores such as ascospores , basidio spores, zygospores and oospores. Some fungi produce useful substances such as penicillin, acetone, butanol sorbitol etc. Some fungi produce antibiotic substances, eg . Penicillin.  Fungi are usually filamentous.

15. FUNGI Fungi play a vital role in the environment economically important as a food source Cells of fungi are quite similar to those of plants, protists , and animals. lack of chlorophyll separates them from plants. Since they do not ingest their food (by eating ) they are not animals. Most fungi reproduce through the generation of spores ( Mycelia sterilia being an exception ). Fungal spores are non-motile (meaning they cannot move of their own accord). This further separates fungi from protists , which also can produce spores, but if they do, they are often motile .

16. Together with bacteria, fungi are the major decomposers of organic materials in the soil. They degrade complex organic matter into simple organic and inorganic compounds and help recycle carbon, nitrogen, phosphorous, and other elements for reuse by other organisms. As molds grow by digesting the organic material, they gradually destroy whatever they grow on. Cause many plant and human diseases.

17. MOLDS Molds belong to the fungus family Molds are multicellular , filamentous fungi Moulds are microscopic, plant-like org’s , Growth can be easily recognised by it's cottony appearance. V ery common organisms that grow on food materials to spoil the foods and can be easily be identified

18. Structure The thallus (body) of a mold consists of long branching filaments of cells joined together; these filaments are called hyphae ( sing:hypha ). Hyphae can grow to immense proportions. The hyphae of a single fungus in Oregon extend across 3.5 miles.

19. Structure - Hyphae septate hyphae : Hyphae of most molds contain cross-walls called septa which divide them into distinct, uninucleate (one-nucleus) cell-like units --- septate fungi coenocytic hypae : Hyphae of few classes of fungi contain no septa and appear as long, continuous cells with many nuclei. Cytoplasm passes through and among cells of the hypha uninterrupted by cross walls --- coenocytic fungi. Even in fungi with septate hyphae, there are usually openings in the septa that make the cytoplasm of adjacent “cells” continuous; these fungi are actually coenocytic organism.

20. Structure - Hyphae Hyphae grow by elongating at the tips. Each part of hyphae is capable of growth, and when a fragment breaks off, it can elongate to form a new hyphae. In the laboratory, fungi are usually grown from fragments obtained from a fungal thallus . Portion of a hyphae that obtains nutrients is called the vegetative hyphae Portion concerned with reproduction is the reproductive or aerial hypha , so named because it projects above the surface of the medium on which the fungus is growing. Aerial hypae often bear reproductive spores

21. Structure - Mycelium When environmental conditions are suitable, the hypae grow to form a filamentous tangled mass called a mycelium, which is visible to the unaided eye .  

22. Characteristics of Fungal Hyphae: Septate versus Coenocytic

23. Mycelium: Large, Visible Mass of Hyphae

24. GROWTH Molds release countless tiny microscopic cells called spores , which spread easily through the air and form new colonies where they find the right conditions. For molds to grow and reproduce, they need only a food source – any organic material , such as leaves, wood, paper, or dirt – and moisture (relative humidity > 60% ). 

25. Growth of mold Development of fungi cultures usually begins with a spore. In the presence of moisture, the spore swells with water much like a germinating Plant seed. Then the spore wall expands through a preformed weak spot [the germ pore] to create a thin, balloon-like protuberance. This first extension of growth is called a hypha resembling long, worm-like structures. With continued growth, the hyphae will branch and grow into a visible colony called a "mycelium.“

26. FUNGI - NUTRITION All fungi are chemoheterotrophs , requiring organic compounds for energy and carbon. Mostly saprophytes - obtain their nutrients from dead organic matter. Play an important role in the environment by decomposing and recycling organic matter. Few are parasitic on plants causing major losses of crops. Others find their way into humans or other animals and cause serious infections.

27. Nutrition of Fungi The nutritional need of a fungus are facilitated by the enzymes cellulase and/or chitinase . Acquire nutrients by absorption Most are saprobes Some trap and kill microscopic soil-dwelling nematodes Haustoria allow some to derive nutrients from living plants and animals Most are aerobic; some are anaerobic; many yeasts are facultative anaerobes

28. NUTRITIONAL ADAPTATIONS Fungi are generally adapted to environments that would be hostile to bacteria. Fungi are chemo heterotrophs, and, like bacteria, they absorb nutrients rather than ingesting them as animals do. Fungi differ from bacteria in certain environmental and nutritional requirements Fungi usually grow better in an environment with a pH of about 5, which is too acidic for the growth of most common bacteria. Almost all molds are aerobic. Most yeasts are facultative anaerobes.

29. NUTRITIONAL ADAPTATIONS Most fungi are more resistant to osmotic pressure than bacteria; most can therefore grow in relatively high sugar or salt concentrations. Fungi can grow on substances with a very low moisture content, generally too low to support the growth of bacteria. Fungi require somewhat less nitrogen than bacteria for an equivalent amount of growth. Fungi are often capable of metabolizing complex carbohydrates, such as lignin (a component of wood), that most bacteria cannot use for nutrients. 

30. FUNGI - Genome Fungi have relatively very small nuclei, containing very few nucleotides in their genomes. Example: the amount of nucleotides in mushrooms is eight times that in E. coli ( a prokaryote) but is only 1% of that in humans .

31. Cultural Characteristics Some molds look velvety on the upper surface some look dry and powdery some wet or gelatinous. Some molds are loose and fluffy some are compact . some are hard. Some possess pigments in their mycelium ( red,yellow , blue- green, brown, black, pink, orange etc) Mold growth on surfaces can often be seen in the form of discoloration The appearance of the molds indicates its genus.

32. Physiological Characteristics Temperature requirement –Most molds grow well at ordinary temperature Mesophilic and psychrotrophic range. Optimum temperature = 25 to 30 c but few grow well at 35 to 37c or above( Aspergillus ) A number of molds grow well at refrigeration and freezing temperatures : -5 to -10c Few are thermophilic - can grow at a high temperature.

33. Physiological Requirements Moisture requirement – Aw of 0.6 -0.65 Molds require less moisture to grow than yeast and bacteria. If dried food has a moisture content below 14 to 15%, it will prevent or delay mold growth. Xerophilic molds use the humidity in the air as their only water source; other molds need more moisture

34. Physiological Requirements Oxygen Requirement – Molds are aerobic require oxygen for their growth. Fungi are aerobic or facultatively anaerobic , anaerobic. pH : Grow over a wide range of pH(2-8.5) Majority are favored by an acid pH.

35. Media In general can utilize many foods, ranging from simple to complex. Most molds possess a variety of hydrolytic enzymes and some are grown for their amylases, pectinases, lipases and proteinases.

36. Identification Yeast identification, like bacterial identification, involves biochemical tests. However, multicellular fungi are identified on the basis of physical appearance, including colony characteristics and reproductive spores.

37. Where are molds found? Found in virtually every environment and can be detected, both indoors and outdoors, year round. Mold growth is encouraged by warm and humid conditions. Outdoors - they can be found in shady, damp areas or places where leaves or other vegetation is decomposing. Indoors - they can be found where humidity levels are high, such as basements or showers

38. REPRODUCTION Fungi reproduce by the production of spores Fungal spores can be either asexual or sexual . Filamentous fungi can reproduce asexually by fragmentation of their hyphae. Mold reproduce using both sexual and asexual reproduction methods. Molds reproduce through producing very large numbers of small spores , which may contain a single nucleus or be multinucleate . Spores are formed from aerial hyphae Mold spores can be asexual (the products of mitosis) or sexual (the products of meiosis ) Many species can produce both types . Spores are of considerable importance in the identification of fungi At the end of the hyphae are the reproductive structures that produce spores.  Spores are produced on different structures depending on species.

39. Asexual and Sexual Reproduction in fungi Telemorphs : The sexual fungi (perfect, meiotic). They produce sexual spores. A namorph : The asexual fungi (imperfect, mitotic ) Ex: Penicillium is an anamorph that arose from a mutation in a telemorph . Holomorph : the whole fungus, including anamorphs and teleomorph . many fungi can have both, especially Ascomycota -- most have either one or the other

40. Asexual Spores Asexual Spores are called conidia (sing: conidium ) When these spores germinate, they become organism that are genetically identical to the parent cell. Asexual spores are produced by the hypae of an individual fungus through mitosis and subsequent cell division There is no fusion of the nuclei of cells.  

41. Asexual Spores Conidiospore / conidium (plural: conidia): Unicellular or multicellular spores that are produced in a chain at the end of a conidiophores. Such spores are produced by Aspergillus . Conidia are not enclosed in a sac. Blastospores : blastoconidia are produced in a cluster by budding from a parent cell ( conidium ).  consists of buds coming off the parent cell. Such spores are found in yeasts, such as candidia albicans and Cryptococcus.      Sporangiospores : Spores formed within a sporangium, or sac, at the end of an aerial hypha called a sporangiophore . The sporangium can contain hundreds of sporangiospores . Such spores are produced by Rhizopus .  

42. Asexual Reproduction

43. sexual reproduction During sexual reproduction , compatible nuclei unite within the mycelium and form sexual spores. Sexually opposite cells may unite within a single mycelium, or different mycelia. When the cells unite, the nuclei fuse and form a diploid nucleus. Several divisions follow, and the haploid state is reestablished .

44. S exual spores Sexual spores result from the fusion of nuclei from two opposite mating strains of the same species of fungus. Fungi produce sexual spores less frequently than asexual spores. Organism that grow from sexual spores will have genetic characteristics of both parental strains.

45. Sexual Spores Fungal sexual spores results from sexual reproduction which consists of three phases: Plasmogamy (Cell fusion): A haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-). Karyogamy (Nuclear fusion): The (+) and (-) nuclei fuse to form a diploid zygote nucleus. Meiosis. The diploid nucleus gives rise to haploid nuclei (sexual spores), some of which may be genetic recombinants.

46. Oospores are produced when male gametes (reproductive nuclei)enter a large spherical cell ( oogonium ) and fertilize the eggs within. Ascospores are produced within spherical cells called asci most often in groups of 4 or 8 Usually the asci are produced within some kind of enclosing structure and thus are not found exposed on the hyphae.

47. Zygospores : Do not occur inside any kind of enclosing structure produced by the direct fusion of two hyphal protrusions from neighbouring filaments. Usually zygospores are recognized as large, nearly spherical, often dark brown or black, rough-walled spores with two connecting hyphae, representing the two mating gametangia

48. Basidiospores : produced externally on a structure called a basidium . Basidia come in a variety of forms, but those commonly encountered on moulds will be club-shaped and bear four or eight spores on sharp projections at the apex.

49. Common Molds Absidia Alternaria Ascomycetes Aspergillus Basidiomycetes Cladosporium Curvularia Fusarium Mucor Penicillium Pithomyces Stachybotrys Trichoderma Ulocladium

50. Fungal spores - Bacterial endospores Fungal spores are quite different from bacterial endospores . Bacterial endospores allows a bacterial cell to survive adverse environmental conditions. A single vegetative bacterial cell forms one endospore , which eventually germinates to produce a single vegetative bacterial cell. This process is not reproduction because it does not increase the total number of bacterial cells. But after a mold forms a spore, the spore detaches from the parent and germinates into a new mold. Unlike the bacterial endospore , this is a true reproductive spore; a second organism grows from the spore. Although fungal spores can survive for extended periods in dry or hot environment, most do not exhibit the extreme tolerance and longevity of bacterial endospores .

51. YEAST

52. Yeasts Yeasts are single-celled eukaryotic microorganisms. Size : yeasts are 5 to 10 µm in diameter . They are larger than bacteria . Yeasts are non filamentous unicellular fungi. Typically spherical or oval in shape Yeasts consists single nucleus and eukaryotic organelles. classified in the kingdom Fungi, with 1,500 species currently described. estimated to be 1% of all fungal species.

53. Yeast Yeasts are very important economically: - Yeasts are responsible for fermentation of beer and bread. ( Saccharomyces cerevisiae ) - Ethanol production - Wastewater treatment: a mixed culture of yeasts Candida lipolytic Candida tropicalis , and Yarrowia lipolytica grown on hydrocarbons or gas oil.

54. Cytological methods Unstained yeast cells can hardly be visualized by light microscopy. At 1000 fold magnification, it may be possible to see the yeast vacuole and cytosolic inclusion bodies. By phase contrast microscopy together with an appropriate staining technique, several cellular structures can be distinguished. A very convenient tool to localize and even to follow the movement of particular proteins within yeasts cells is the use of the green fluorescent protein (GFP) from the jelly fish ( Acquorea Victoria) as a reporter molecule. Organelle ultrastructure and macromolecular architecture can only be obtained with the aid of EM.

55. Structure of Yeast Cell Yeast cells share most of the structural and functional features of higher Eukaryotes — which has rendered yeast an ideal model for Eukaryotic cell biology. Ultrastructural features observed: Cell wall, periplasm , Plasma membrane, bud scar, cytoplasm, nucleus, mitochondria, Endoplasmic reticulum, Golgi Apparatus, Secretory vesicles, vacuole, peroxisomes.

56. Structure of Yeast Cell In contrast to mammalian cells, peculiarities of yeast cells are that they are surrounded by a rigid cell wall and develop birth scars during cell division, the vacuole corresponds to lysosomes is higher cells. Bud scars are specialized, ring –shaped convex protrusions at the cell surface which remain on the mother cells (of budding yeasts) after cell division and birth of daughter cells. The concave indentations remaining on the surface of the daughter cell after budding are called birth scars.

57. Structure of Yeast Cell Yeast cytoplasm is an acidic (pH 5.25) colloidal fluid. Cytoskeleton comprises the microtubules and the microfilament. Freely suspended 80s ribosomes Yeast nucleus is a round lobate organelle 1.5 μm in diameter. yeast nuclear DNA can be isolated as linear molecules ranging in size from 10 μm - 50 μm . Endoplasmic Reticulum is the site of bio synthesis and modifications of proteins that are to be exported.

58. Structure of Yeast Cell From ER, proteins are directed to the Golgi Apparatus by vesicles, which fuse at the Cis side and are exported from the Golgi Apparatus at the trans side. In Golgi further modifications of the protein by carbohydrate side chains may take place. Proteins delivered from the Golgi are directed to different destination within the cell or to the exterior via different secretory vesicles to the vacuole, the bud region during mitosis, the plasma membrane , the periplasm . Peroxisomes (membrane-enclosed organelles that contain enzymes involved in a variety of metabolic reactions, including several aspects of energy metabolism) perform a variety of metabolic functions in Eukaryotic cells. Mitochondria – under aerobic conditions, yeast mitochondria are involved in ATP synthesis coupled to oxidative phosphorylation

59. Yeasts Like molds, yeasts are widely distributed in nature; they are frequently found as a white powdery coating on fruits and leaves.

60. Reproduction Most yeasts reproduce asexually. Yeasts grow as single cells producing daughter cells either by an asymmetric division process called Budding - the budding yeasts or by B inary fission (splitting in two) - the fission yeasts . Budding : a small bud cell forms on the cell, which gradually enlarge and separate from the mother cells. Most of the yeasts reproduce by budding. Baker’s yeast, Saccharomyces cerevisiae .

61. Budding In budding the parent cell forms a protuberance (bud) on its outer surface. As the bud elongates, the parent cell’s nucleus divides, and one nucleus migrates into the bud. Cell wall material is then laid down between the bud and parent cell, and the bud eventually breaks away. Yeasts reproduce rapidly. One yeast cell can in time produce up to 24 daughter cells by budding. Budding yeasts divide unevenly ( Saccharomyces )

62. Budding

63. Bud Scar

64. Bud Scar

65. P seudohypha Some yeasts produce buds that fail to detach themselves; these buds form a short chain of cell called a pseudohypha . Candida albicana attaches to human epithelial cells as a yeasts but usually requires pseudohypha to invade deeper tissues

66. Fission : similar to budding During this parent cells elongates, grow to certain size its nucleus divides, and two equal daughter cells are produced . Only a few yeast species reproduce by fission. e.g . Schizosaccharomyces divide evenly to produce two new cells.

67. Yeast respiration Yeasts are facultative anaerobes, which allows them to grow in a variety of environments. When oxygen is available, they carry out aerobic respiration. When oxygen is not available, they ferment carbohydrates to produce ethanol and carbon dioxide . Yeasts can use oxygen or an organic compound as the final electron acceptor; this is valuable attribute because it allows these fungi to survive in various environments. If given access to oxygen, yeasts perform aerobic respiration to metabolize carbohydrate to carbon dioxide and water Denied oxygen, they ferment carbohydrates and produce ethanol and carbon dioxide. This fermentation is used in the brewing, wine-making, and baking industries. Saccharomyces species produce ethanol in brewed beverages and Co 2 for leavening bread dough .

68. Morphology Yeast size can vary greatly depending on the species, typically measuring 4 -12 µm long and 3–4 µm in diameter, although some yeasts can reach over 40 µm in diameter. spherical or oval in shape some species of yeast forms may become multicellular through the formation of strings of connected budding cells known as pseudohyphae as seen in most molds

69. Nutrition and growth Yeasts are chemoorganotrophs, as they use organic compounds as a source of energy and do not require sunlight to grow. Carbon is obtained mostly from hexose sugars, such as glucose and fructose, or disaccharides such as sucrose and maltose. Some species can metabolize pentose sugars such as ribose, Xylose Some species can metabolize alcohols and organic acids. Yeast species require oxygen for aerobic cellular respiration (obligate aerobes) or are anaerobic(fermentative yeast), facultative anaerobes.

70. Cultural Characterstics yeasts are grown in the laboratory on solid growth media or in liquid broths. They grow especially well in substances containing sugar. Increase in the number of yeasts cells on a solild medium produce a colony similar to a bacterial colony. Common media used for the cultivation of yeasts include potato dextrose agar or potato dextrose broth Wallerstein Laboratories nutrient agar yeast peptone dextrose agar yeast mould agar or broth.

71. Cultural Characterstics Temperature: Yeasts vary in temperature range they grow best. Optimum = 25 to 30c Maximum about 35 to 47c Some grow at 0c or less pH : 4 to 4.5 Yeasts grow best in a neutral or slightly acidic Ph Will not grow well in alkaline medium unless adapted to it.

72. Cultural Characterstics Water activity/moisture : 0.7 to 0.8 Osmophilic yeasts can grow at even low aW . Require less moisture than majority of bacteria and more moisture than molds. Can grow in the presence of high concentration of solutes(sugar/salt)

73. Cultural Characterstics They differ from most fungi, which grow as thread-like hyphae. But this distinction is not a fundamental one, because some fungi can alternate between a yeast phase and a hyphal phase, depending on environmental conditions. Such fungi are termed dimorphic

74. Cultural characteristics For the most part, the appearance of massed yeast growth is not useful in the identification of yeasts, although growth as a film on the surface of liquid media suggests an oxidative or film yeast. Some produce pigments (carotenoid pigment indicates the genus Rhodotorula ) - causes colored spots on foods. It is difficult to tell yeast colonies from bacterial ones on agar plates; the only certain way is by means of microscopic examination of the organisms. Most young yeast colonies are moist and somewhat slimy but may appear mealy; most colonies change little with age and become dry and wrinkled. Yeasts are oxidative, fermentative, or both. The oxidative yeasts may grow as a film, pellicle, or scum on the surface of a liquid and then are termed film yeasts. Fermentative yeasts usually grow throughout the liquid and produce carbon dioxide.

75. F ungi - dimorphic Some fungi, most notably the pathogenic species, exhibit dimorphism —two forms of growth. Such fungi can grow either as a mold or as a yeasts. They have the ability to shift from the yeast form to the mold form and vice versa. Many fungal pathogens exist in the body in the yeast form but revert to the mold form in the laboratory when cultivated. The mold like forms produce vegetative and aerial hyphae; the yeast like forms reproduce by budding. Dimorphism in pathogenic fungi is temperature-dependent: at 37 C, the fungus is yeast like, and at 25 C, it is mold like. However, the appearance of the dimorphic fungus changes with CO 2 concentration.

76. Fungal Infections These infections are occurring as nosocomial infections and in people with compromised immune systems. In addition, thousands of fungal disease afflict economically important plants, costing more than one billion dollars annually.

77. Fungi are also beneficial They are important in the food chain because they decompose dead plant matter, thereby recycling vital elements. Through the use of extracellular enzymes such as cellulases , fungi are the primary decomposers of the hard parts of plants, which cannot be digested by bacteria and animals. Nearly all plants depend on symbiotic fungi, known as mycorrhizae , which help their roots absorb minerals and water from the soil. Fungi are also valuable to animals. Fungi-farming ants cultivate fungi that break down cellulose and lignin from plants, providing glucose that the ants can then digest. Fungi are used by humans for food (mushrooms) and to produce foods (bread and citric acid) and drugs (alcohol and penicillin). Of the more than 100,000 species of fungi, only about 200 are pathogenic to humans and animals

78. The Significance of Fungi Decompose dead organisms and recycle their nutrients Form associations with roots of vascular plants, which help plants absorb water and minerals Used for food, in religious ceremonies, and in manufacture of foods and beverages Produce antibiotics Serve as important research tools 30% cause diseases of plants, animals, and humans Can spoil fruit, pickles, jams, and jellies

79. Many fungi are very useful to humans yeasts-- baking and brewing antibiotics--- e.g. penicillin & cephalosporin other drugs-- e.g. cyclosporin many organic acids are commercially produced with fungi-- e.g. citric acid in Coke is produced by an Aspergillus steroids and hormones--- e.g. the pill certain “stinky” cheeses-- e.g. blue cheese, Roquefort and Camembert

80. Fungi are important experimental /model org’s for genetics, cell biology and molecular biology! easily cultured, occupy little space, multiply rapidly, short life cycle. study metabolite pathways ,growth, development, and differentiation mechanisms of cell division and development microbial assays of vitamins and amino acids