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13.04.09 Phase I/ Module VII Dr Ekta, Microbiology 1 Classification & General Properties of Fungi.

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Presentation on theme: "13.04.09 Phase I/ Module VII Dr Ekta, Microbiology 1 Classification & General Properties of Fungi."— Presentation transcript:

1 Phase I/ Module VII Dr Ekta, Microbiology 1 Classification & General Properties of Fungi

2 Phase I/ Module VII Dr Ekta, Microbiology 2 Introduction Mykes (Greek word) : Mushroom Fungi are eukaryotic protista; differ from bacteria and other prokaryotes. 1. Cell walls containing chitin (rigidity & support), mannan & other polysaccharides 2. Cytoplasmic membrane contains ergosterols 3. Possess true nuclei with nuclear membrane & paired chromosomes. 4. Divide asexually, sexually or by both 5. Unicellular or multicellular

3 Phase I/ Module VII Dr Ekta, Microbiology 3 Introduction Simplest fungus :- Unicellular budding yeast Hypha :- Elongation of apical cell produces a tubular, thread like structure called hypha Mycelium :- Tangled mass of hyphae is called mycelium. Fungi producing mycelia are called molds or filamentous fungi. Hyphae may be septate or non-septate

4 Phase I/ Module VII Dr Ekta, Microbiology 4 CLASSIFICATION Depending on cell morphology 1. Yeasts 2. Yeast like fungi 3. Molds 4. Dimorphic fungi

5 Phase I/ Module VII Dr Ekta, Microbiology 5 1. Yeasts Unicellular fungi which reproduce by budding On culture - produce smooth, creamy colonies e. g Cryptococcus neoformans (capsulated yeast)

6 Phase I/ Module VII Dr Ekta, Microbiology 6 2. Yeast like fungi Grow partly as yeasts and partly as elongated cells resembling hyphae which are called pseudohyphae. e.g. Candida albicans

7 Phase I/ Module VII Dr Ekta, Microbiology 7 3. Molds/ Filamentous fungi Form true mycelia & reproduce by formation of different types of spores. Vegetative/ aerial hyphae e.g. Rhizopus, mucor

8 Phase I/ Module VII Dr Ekta, Microbiology 8 4. Dimorphic fungi Occur in 2 forms Molds (Filaments) – 25 C (soil) Yeasts – 37 C (in host tissue) Most fungi causing systemic infections are dimorphic: Histoplasma capsulatum Blastomyces dermatidis Paracoccidioides brasiliensis Coccidioides immitis Penicillium marneffei Sporothrix schenkii

9 Phase I/ Module VII Dr Ekta, Microbiology 9 Reproduction in fungi Sexual - formation of zygospores, ascospores or basidiospores Asexual reproduction – budding or fission Asexual spores are formed on or in specialized structures. Vary in size, shape & colour but these characteristics are constant for a particular species.

10 Phase I/ Module VII Dr Ekta, Microbiology 10 Reproduction in fungi Micro conidia - Small, single celled Macro conidia – Large, single or many celled

11 Phase I/ Module VII Dr Ekta, Microbiology 11 Systematic classification Based on sexual spore formation: 4 classes 1. Zygomycetes 2. Ascomycetes reproduce sexually 3. Basidiomycetes 4. Deuteromycetes (fungi imperfectii)

12 Phase I/ Module VII Dr Ekta, Microbiology Zygomycetes Lower fungi Broad, nonseptate hyphae Asexual spores - Sporangiospores: present within a swollen sac- like structure called Sporangium

13 Phase I/ Module VII Dr Ekta, Microbiology Zygomycetes Sexual spores - Zygospore: a resting, thick walled cell in between hyphae e.g. Rhizopus, Mucor

14 Phase I/ Module VII Dr Ekta, Microbiology Ascomycetes Includes both yeasts & filamentous fungi Narrow, septate hyphae Asexual spores are called conidia borne on conidiophore

15 Phase I/ Module VII Dr Ekta, Microbiology Ascomycetes Sexual spores called ascospores are present within a sac like structure called Ascus. Several asci may be seen within a fruiting body as seen in Penicillium, Aspergillus Each ascus has 4 to 8 ascospores.

16 Phase I/ Module VII Dr Ekta, Microbiology Basidiomycetes Sexual fusion results in the formation of a club shaped organ called base or basidium which bear spores called basidiospores

17 Phase I/ Module VII Dr Ekta, Microbiology Deuteromycetes or Fungi imperfectii Group of fungi whose sexual phases are not identified. Grow as molds as well as yeasts. Asexual stage – conidia e.g. Candida, Cryptococcus

18 Phase I/ Module VII Dr Ekta, Microbiology 18 Vegetative Structures of Fungi Arthrospores – formed by segmentation & condensation of hyphae Chlamydospores – thick walled resting spores e.g. C.albicans

19 Phase I/ Module VII Dr Ekta, Microbiology 19 Fungal Infections/ Mycoses Superficial mycoses : 2 types: surface and cutaneous mycoses Skin, hair & nails. Mild but chronic disease Deep mycoses : 2 types: subcutaneous & systemic mycoses Caused by soil saprophytes Infection is accidental Range from a symptomatic infection to fatal disease

20 Phase I/ Module VII Dr Ekta, Microbiology 20 Superficial: Surface mycoses Live exclusively on dead surfaces of skin and its appendages No contact with living tissue, hence no inflammatory response 1. Tinea versicolor 2. Tinea nigra 3. Piedra

21 Phase I/ Module VII Dr Ekta, Microbiology 21 Superficial: Cutaneous mycoses Cornified layer of skin & its appendages Contact with living tissue, hence inflammatory & allergic responses seen 1. Dermatophytes – skin, hair & nails 2. 3 genera - Trichophyton Microsporum Epidermophyton

22 Phase I/ Module VII Dr Ekta, Microbiology 22 Deep mycoses Subcutaneous mycoses 1. Mycotic Mycetoma 2. Chromoblastomycoses 3. Sporotrichosis 4. Rhinosporidiosis Systemic mycoses 1. Cryptococcoses 2. Blastomycosis 3. Coccidioidomycoses 4. Histoplasmoses

23 Phase I/ Module VII Dr Ekta, Microbiology 23 Candidiasis Caused by candida sps, forms a bridge between superficial & deep mycoses as it can cause cutaneous as well as systemic infections Can also cause opportunistic infections

24 Phase I/ Module VII Dr Ekta, Microbiology 24 Opportunistic infections Pts with debilitating disease, altered physiological state Mainly caused by fungi which are common lab contaminant on culture media Aspergillus Pencillium Mucor Rhizopus Produce serious & fatal infections

25 Phase I/ Module VII Dr Ekta, Microbiology 25 Useful Properties of Fungi Source of food e.g. mushrooms Fermentation - Production of alcohol, bread, cheese e.g. Sacchromyces spps Antibiotic production e.g. Penicillin from Penicillium notatum

26 Phase I/ Module VII Dr Ekta, Microbiology 26 Useful Properties of Fungi Ergot from Claviceps purpurea, used to induce uterine contractions Vaccines for Hepatitis B – Sacchromyces cerevisiae

27 Phase I/ Module VII Dr Ekta, Microbiology 27 Learning Objectives Describe the general characteristics of fungi Discuss the major classes of fungi and list examples Discuss the criteria upon which fungi are categorized Explain the formation of both asexual and sexual spores for reproduction Discuss the medical & industrial importance of fungi Learning Resources: Lecture notes Textbook of Microbiology, R. Ananthanarayan Ch 65


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