Upload
michelle-whitaker
View
233
Download
6
Tags:
Embed Size (px)
Citation preview
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
1
Classification & General Properties of Fungi
13.04.09 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
13.04.09 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
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
4
CLASSIFICATION
Depending on cell morphology 1. Yeasts
2. Yeast like fungi
3. Molds
4. Dimorphic fungi
13.04.09 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)
13.04.09 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
13.04.09 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
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
8
4. Dimorphic fungi Occur in 2 forms Molds (Filaments) – 25C (soil)
Yeasts – 37C (in host tissue)
Most fungi causing systemic infections are dimorphic: Histoplasma capsulatum Blastomyces dermatidis Paracoccidioides brasiliensis Coccidioides immitis Penicillium marneffei Sporothrix schenkii
13.04.09 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.
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
10
Reproduction in fungi
Micro conidia - Small, single celled
Macro conidia –
Large, single or many celled
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
11
Systematic classification Based on sexual spore formation: 4
classes1. Zygomycetes
2. Ascomycetes reproduce sexually
3. Basidiomycetes
4. Deuteromycetes (fungi imperfectii)
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
12
1. Zygomycetes
Lower fungi
Broad, nonseptate hyphae
Asexual spores - Sporangiospores: present within a swollen sac- like structure called Sporangium
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
13
1. Zygomycetes
Sexual spores - Zygospore: a resting, thick walled cell in between hyphae
e.g. Rhizopus, Mucor
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
14
2. Ascomycetes Includes both yeasts & filamentous fungi
Narrow, septate hyphae
Asexual spores are called conidia borne on conidiophore
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
15
2. 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.
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
16
3. Basidiomycetes
Sexual fusion results in the formation of a club shaped organ called base or basidium which bear spores called basidiospores
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
17
4. Deuteromycetesor 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
13.04.09 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
13.04.09 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
13.04.09 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
13.04.09 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
13.04.09 Phase I/ Module VII Dr Ekta, Microbiology
22
Deep mycoses
Subcutaneous mycoses 1. Mycotic Mycetoma
2. Chromoblastomycoses
3. Sporotrichosis
4. Rhinosporidiosis
Systemic mycoses1. Cryptococcoses
2. Blastomycosis
3. Coccidioidomycoses
4. Histoplasmoses
13.04.09 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
13.04.09 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
13.04.09 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
13.04.09 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
13.04.09 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:Learning Resources: Lecture notes Textbook of Microbiology, R. Ananthanarayan Ch 65