Fungi

INTRODUCTION11Course No. BT 331Cr Hr. 2+1 (3)Microbiology3rd SemesterProf. Dr. Farrukh Hussain

2COURSE OBJECTIVESThe Mycology course will cover various taxonomic, morphological, reproductive and economic aspects of fungi.Some major areas are taxonomic, morphology, reproduction and life processes of some important fungi.3TEACHING METHODSPower point presentations will be frequently used for definitions, illustrations, figures and explanation of the topics.The medium of instruction will be primarily English. However, help in Urdu and Pushto can not be denied.The students will submit assignments as and when required in hard and soft copies.

4Attend the classes regularly.Revise the required topics.Please come to the class on time as late coming disturbs the class and teacher.Keep on taking lecture notes.Communicate on the following email:farrukh.biotech@suit.edu.pk5Introduction to courseGRADING POLICY

Mid Term Exam=25%Final Term Exam=50%Practical, Quizzes, Assignment= 25%6NOW WE COME TO THE SUBJECT7LIFE ON EARTH

Living EnvironmentNon living Environment

8Living Environmentincludes organisms of various evolutionary levels9These include all organisms classified in 5 KingdomsANIMALSPLANTSFUNGIBACTERIA (MONERA)PROTISTS10The collective study of all these groups of organisms is called BIOLOGY.This mean the study of the various aspects of organism such as taxonomy, ecology, behaviour & reproduction etc.With advancement of knowledge the subject Biology was over burdened. 11Thus, Biology was conveniently divided into two traditional major branches namely:

BOTANY: The study of plants.

ZOOLOGY: The study of animals.12Even these two subjects got split in to many new disciplines like:MicrobiologyBiotechnologyBiochemistryBioinformaticsEnvironmental BiologyEthnobiologyetc etc.13Botany by itself developed many branches:14Plant PhysiologyPlant TaxonomyPlant AnatomyPlant MorphologyPlant MorphogenesisPlant EcologyPlant GeneticsPlant PathologyPlant Conservation

LimnologyBryologyPteridologyPhycologyEthnobotanyMycologyetc etc

What is MYCOLOGY?It is the study of FungiMykos= mushroom Logos = discourse

the scientist studying Mycologist is called Mycologist.

15Then What is Fungi?(Fungus: Singular)The term fungus is restricted to: thallophytes with: nucleated, spore-bearing, achlorophyllous, heterotrophic, eukaryotic organisms reproducing sexually and asexually.16Fungi are usually filamentous, branched somatic structuresFilaments are normally surrounded by walls containing cellulose or chitin or both. non-motile and reproduce by spores.They are not differentiated into root, stem and leaves. do not possess any vascular system

17Fungi generally take food by absorption. They may be:saprophytes or parasites

18Described speciesmore than 5000 genera and 50,000 to 100,000 speciesEstimated speciesApproximately 1.5 millionThis renders fungi one of the least-explored biodiversity resources of our planet.

19HABITdiversified in their form. may range in size from unicellular microscopic forms like yeast to macroscopic fleshy agarics (mushrooms) and polypores (bracket fungi)20

Unicellular Yeast cellsAscomycota21

21HABITATfungi are found in water, above and below soil, inside and on the bodies of other living things. They are saprophytic or parasitic and therefore can grow in light or darkness.22HYPHA AND MYCELIUMTypically, the fungal thallus consists of microscopic thread like structure or filaments. The filaments branch in all directions and spread over or into the substratum, which is utilized for food. 23Each of these filaments is known as a hypha (hyphe= web: plural hyphae). A hypha is transparent and tube-like structure filled with a layer of protoplasm. The chemical composition of the cell wall is variable. In may be cellulose or chitin. 24Fungi possess Cell wallorganized nuclei with a nuclear membrane, a nucleolus, Mitochondrion,golgi apparatus and chromosomes

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Hyhae are commonly colourless and their mass has a whitish appearance in some species. Various pigments like green, black, yellow, blue, violet or red may also be present in cell wall, which impart colour to the thallus.

26 The hyphae of some fungi are coenocytic, i.e. they have no septa and their nuclei are more or less uniformly scattered throughout the cytoplasm. Such fungi are called as coenocytes, e.g. lower fungi or Phycomycetes.27

CoenocyticSeptateThe hyphae of higher (Ascomycetes, Basidiomycetes) are septate and divided into large or short cells by transverse walls or septa

The mass of the hyphae forming the thallus of a fungus is called the mycelium (plural: mycelia; mykes= mushroom).28

Frequently the hyphae forming the mycelium become closely woven together into long string-like stands or flat spreading sheets resembling soft felt or tough leather.29REPRODUCTION

Three methods vegetativeasexual sexual

30A. Vegetative Reproduction It is accomplished by following methods.

1. By Fragmentation2. By Fission3. By Budding3. By Spawn5. By Sclerotia

311. By FragmentationThe hyphae break up into pieces or fragments accidentally or through external forces. Each piece grows into a new individual. 322. By Fission Like bacteria, fission takes place in yeast cells. The cell is split into two daughter cells by simple constriction or transverse wall

333. By BuddingIn Sacharomyces (Yeast) the parent cell produces buds, which separate from the parent cell and develop into new individuals. Sometimes, chains of buds forming a short pseudomycelium are produced

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Budding Yeast CellsYeasts Budding

Saccharomyces35Bread and wine yeast, the budding yeast, SaccharomycesEasily cultured. For a time, this was the most important organism for studying the molecular genetics of eukaryotesThus, Saccharomyces is arguably the most important organism known to humansCandida causes diseases of humans, usually experiencing chemical imbalance or immune problems4. Spawn These are blocks of mycelium mixed with a suitable substratum, which is used for cultivation in a suitable growth medium or beds. Mushrooms are commercially cultivated by this method.

365. SclerotiaThese are compact hard masses of hyphae, which serve as perennating organs. Sclerotia may be formed either singly as in ergot (Claviceps) or a large number of these may be produced in one mycelium, e.g. in Botrytis, which causes a number of plant diseases.

37B. Asexual ReproductionAsexual reproduction does not involve the union of nuclei, sex cells or sex organs. Almost all fungi reproduce asexually by means of spores.Spores may be colourless, green, yellow, orange, red, brown or black. 38Reproduce by sporesSpores may be Formed:Directly on hyphaeInside sporangiaOn Fruiting bodies

Amanita fruiting bodyPilobolus sporangiaPenicillium hyphae39Fungi reproduce by releasing spores that are produced either sexually or asexually.The output of spores from one reproductive structure is enormous, with the number reaching into the trillions.Dispersed widely by wind or water, spores germinate to produce mycelia if they land in a moist place where there is food.

Spores range in size from minute to large structures. The shape may be globose, oval, oblong, needle-shaped or helical There may be one or many thousand spores in a spore forming body. The spore producing body is called sporophore. 40 ASEXUAL REPRODUCTIONTypes of Fruiting Bodies:BasidiaSporangiaAscus41

BasidiaSporangia41Generally spores are surrounded by two walls. The external, known as exine or exosporium, is often thick and ornamental.The inner wall, the intine or endosporium, is generally thin and transparent.

42The spores are of two main types on the basis of their mode of origin.a. Asexually produced sporesb. Sexually produced spores

43a. Asexually produced sporesSuch spores originate asexually and are most prevalent among all kinds of fungi. These spores may be borne in sporangia (singular= sporangium; sporos= seed, spore+angeion=vessel).

44A sporangium is a sac-like structure whose entire contents are converted into one or more spores. Sporangiospores may be motile and called zoospores or non-motile and called aplanospores. Zoospores have two flagella, which may be of whiplash and tinsel types. 45ZYGOmycota46

46Asexually produced spores are of the following types:1. Endospores2. Conidia3. Oidia4. Chlamydospores5. Pycniospores

471. EndosporesThe division of the protoplasm within an enlarged cell called sporangium produces these spores endogenously. They are borne at the end of a special hypha called the sporangiophore. The endospores are usually non-motile and bounded by cell wall.

482. ConidiaThey are produced by the development of a constriction at the end of special hyphal branches called the conidiophores These spores are non motile and may be produced either singly or in chains. The tip of the conidiophore may be spherical(Aspergillus) and gives out a number of small peg-like structures called sterigmata.

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These then bear chains of conidia, which are arranged in a basipetal manner (i.e. the youngest conidia are at the base). In Penicillium, the sterigmata bearing chains of conidia are simply ends of a repeatedly dichotomous, branch-like conidiophore, which bear conidia in acropetal order (i.e. the youngest conidia are at the tip).503. OidiaIn several fungi such as in Mucor, the hyphae forming the mycelium often become divided by transverse walls into a large number of short segments, each of which is capable of germinating and developing into a new plant. These segments are called arthrospore or Oidia (sing. oidium; oidion= small egg). They may remain united in chains or become free from each other

514. Chlamydospores

Chlamydospores (Chlamps= mantle + sporos= seed, spore) are produced like oidia but they are thick-walled and black or brown in colour.They are either terminal or produced at regular intervals along the hyphae. Chlamydospores on germination produce a short hypha bearing sporangia or conidia.

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5. PycniosporesThese are small conidia-like bodies produced in pear-shaped cavities called pycnia or pycnidia. In the rusts, special forms of binucleate summer spores called uredospores and teleutospores are produced in clusters called the uredosori or uredinia and teleutosori or telia.

53b. Sexually produced sporesSexually produced spores occur among Phycomycetes and Ascomycetes. They may be Zygospore (Zygomycetes), Oospore (Oomycetes), Ascospore (Ascomycetes) and Basidiospores (Basidiomycetes).

54ZygomycotaSexual spores are produced by conjugation when (+) hyphae and (-) hyphae fuseSexual spores are called ZYGOSPORESZygospores can endure harsh environments until conditions improve

zygospore55Most of the 600 zygomycote, or zygote fungi, are terrestrial, living in soil or on decaying plant and animal material.

Asexual reproduction in sporangia

One zygomycote group form mycorrhizas, mutualistic associations with the roots of plants.

1. Zygospore

Fusion of haploid cells produces one zygospore

2. AscosporeFormed in a sac (ascus)

3. BasidiosporeFormed externally on a pedestal(basidium)

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C. Sexual ReproductionThe union of two nuclei characterizes sexual reproduction. In the formation of reproductive organs, either asexual or sexual, the entire thallus may be converted into one or more reproductive structures.Sexual reproduction occurs under stress and poor habitat conditions57In this way the somatic and reproductive phases do not occur together in the same individual. Such fungi are known as holocarpic (holo= whole+karpos= fruit). There are no male and female fungus

58In the majority of fungi, the reproductive organs arise from a portion of the thallus only, while the remainder continues its normal somatic (vegetative) activities. Such fungi are termed as eucarpic (eu= good+karpos= fruit). Holocarpic fungi are usually less differentiated and considered to be primitive than the eucarpic.59Sexual reproduction consists of three distinct phases.Phase I: PlasmogamyPlasmogamy (plasm= a model object i.e. being+gamos= union, marriage) involves union of two protoplasts, thus bringing two haploid nuclei together. This phase is then followed by the next phase.

60Phase II: KaryogamyKaryogamy (karon=nut, nucleus+gamos= marriage) involves the fusion of two haploid nuclei and formation of a diploid nucleus called synkaryon. In lower fungi, karyogamy follows the plasmogamy immediately.61However, in higher fungi these two processes are separated in time and space. Plasmogamy simply results in the formation of a binucleate cell containing one nucleus of each sex. Such a pair of nuclei is known as dikaryon (di=two+karyon= nut, nuclei). These two nuclei fuse considerably late in the life history of the fungus.62Meanwhile, during growth and cell division of the binucleate cell, the dikaryotic condition may be perpetuated from cell to cell by simultaneous division (conjugate division of two closely associated nuclei and by the separation of resulting sister nuclei into two daughter cells).

63Phase III: MeiosisMeiosis means reduction. Ultimately nuclear fusion takes place in all sexually reproducing fungi and produce the Diploid Zygote. This nuclear fusion is then followed by meiosis, which reduces the number of chromosomes to haploid in the daughter nuclei to produce haploid nuclei.

64Thus fungi have haploid or haplophase (1n) and diploid or diplophase (2n). The hyphae are called as haplont or diplont according to the number of chromosomes in their nuclei.In a true sexual cycle, these three phases occur in a regular sequence and usually at specified points.

65When both the sexes occur on the same thallus, they are called as monoecious or homothallic. Such fungi are bisexual and represented by + sign. When the male and female sexes occur on different thalli, they are called as dioecious or heterothallic and are represented by + or - signs depending upon their sexual tendencies.

66The sex organs of fungi are called gametangia (sing. gametangium: gametes= husband+angion= vessel). These may form differentiated sex cells called gametes or instead may contain one or more gamete nuclei.67If the gametes and gametangia are morphologically identical they are known as isogametes and isogametangia

Anisogametes are morphologically similar bur differ in size68When the gametes are not identical in size and structure, they are called heterogametes and heterogametangia In this case the male gametangium is called the antheridium (antheros= flowery), while the female is called as oogonium (egg). The male gamete is known as antherozoid and the female as an egg or oosphere.

69Plasmogamy brings two compatible nuclei together. This may be done by one of the following methods.1. Planogametic copulation2.Gametangial copulation3. Gametangial contact4. Spermatization5. Somatogamy

701. Planogametic copulationThis involves fusion of two naked gametes. One or both may be motile Motile gametes are called Plasmogametes. The most primitive fungi produce isogamous plasmogametes. Anisogamous plasmogametes differ in size. When the female gamete is non-motile and male motile, the latter enters the oogonium and fertilizes the egg. This is known as oogamy.

712. Gametangial copulationIn this method the entire contents of two contacting gametangia fuse.3. Gametangial contactThe gametes are reduced to undifferentiated protoplasts. Each consists of a nucleus. Such gametes are never released from the gametangium but transferred directly from one gametangium into the other through a pore or tube developed in the gametangial wall.

724. SpermatizationNumerous minute, uninucleate, spore-like male structures are produced in various ways. These are then carried by insects, wind or water to female gametangia. A pore develops at place of contact and the spermatia pass into the female organ.

735. SomatogamyMany higher fungi do not produce sex organs, but the somatic cells take over the sexual function

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