Unit 2 (Fungi)

Question 1

Fungi

Answer 1

• large group of plants without chlorophyll that live as heterotrophic, saprophytes or parasites
• produce both sexually and asexually

Question 2

Fungi that reproduce sexually and cause human infections (4)

Answer 2

• zygomycetes
• ascomycetes
• basidiomycetes

Question 3

Zygomycetes

Answer 3

• product of sexual reproduction is a resting diploid spore, zygospore
• example:Rhizopus

Question 4

Ascomycetes

Answer 4

• all produce sexually with asci and ascospore
• example: Saccharomyces cerevisiae

Question 5

Basidiomycetes

Answer 5

• all produce sexaully with basidia and basidiospores
• example: Mushrooms

Question 6

Deuteromycetes

Answer 6

• fungi lacking sexual reproduction
• example: Aspergillus fumigatus

Question 7

Most pathogenic fungi are members of the …

Answer 7

• ascomycetes, with only a few being basidiomycetes

Question 8

Fungal infections of the skin, intestinal tract, lungs and brain are frequent in people with a ?

Answer 8

• depressed immune system

Question 9

Mycology

Answer 9

• study of fungal pathogens

Question 10

Mycosis

Answer 10

• disease caused by fungi
• not fatal, but are difficult to treat, without harming the tissue that hosts them

Question 11

Fungi are a diverse group of heterotrophs, many are:

Answer 11

• saprophyte that digest dead organic matter or wastes
• parasites that obtain nutrients from the tissues of living organisms
• multi-cellular moulds and consist of branched filaments
• uni-cellular yeasts
• dimorphic fungi adapt a filamentous structure when growing as saprophytes and a yeast phase when parasitic

Question 12

Which organism is able to withstand extreme environmental conditions better that most other organisms?

Answer 12

fungi

Question 13

2 main types of morphology forms associated with human infection

Answer 13

• yeast
• filamentous (mould)

Question 14

Yeast

Answer 14

• uni-cellular fungi that reproduce by an asexual budding process
• larger than bacteria
• thallus is usually a chain or filament of cells
• the cells are eggshaped, but some are elongated while others are spherical
• the thallus consists of a cell wall, protoplasma, nucleus and sometimes a capsule
• posses no flagella

Question 15

Filamentous (mould)

Answer 15

• fungus whose vegetative form is a mass of hyphae, each hyphae grows by apical extension

Question 16

Thallus

Answer 16

• body of a filamentous fungi
• the thallus of a multi-cellular fungus consists of a mycelium, which is a mass of filaments called hyphae

Question 17

Cell wall

Answer 17

• contain cellulose or chitin, a polysaccharide that surrounds the protoplasma
• rigid and conveys shape to the fungus

Question 18

Septum

Answer 18

• cross walls

Question 19

Moulds that affect the skin do not have

Answer 19

• flagella, but can move by growing new hyphae

Question 20

Septal pore

Answer 20

• allows the cytoplasma and nuclei to pass between cells

Question 21

Woronin body

Answer 21

• fungi with a single septal pore contain this organelle
• blocks the pore of a damaged cell, to prevent materials from this cell to enter a healthy cell

Question 22

Substrate

Answer 22

• growth medium and mycelium cells release enzymes that digest the surface and absorb nutrient molecules

Question 23

Unlike bacteria, fungi cannot use

Answer 23

• inorganic carbon dioxide as the sole source of carbon
• carbon and nitrogen are obtained from the substrate
• many fungi synthesize their own carbohydrates using organic carbon and stored glycogen in granules in the cytoplasma

Question 24

Lysosomal enzymes

Answer 24

-all fungi produce these and they digest damaged cells and assist parasitic fungi to invade hosts

Question 25

Fungi reach the host by means of ?

Answer 25

- spores carried by the wind or water - transferred from insects and animals

Question 26

Invasion requires

Answer 26

- proximity to host - ability to penetrate the host - ability to digest and absorb nutrients from host cells

Question 27

Optimum temp for saprophytes is

Answer 27

22-37 - some will however, grow at or near zero

Question 28

Optimum pH

Answer 28

3.8- 5.6 - fungi are more tolerant of acidic conditions than most other microbes

Question 29

Aerobic vs facultative

Answer 29

- need oxygen - able to live under various conditions

Question 30

Usually moulds and many yeast are

Answer 30

- aerobic, but some yeasts are facultative

Question 31

Asexual reproduction

Answer 31

- involves mitotic cell division, which in a yeast occurs by budding and in a mould by spore formation

Question 32

Sexual reproduction

Answer 32

- fungi are able to produce gametes and sexual reproduction occurs - when 2 gametes, from different cells, unite and the cytoplasms mingle in a process called plasmogamy - when 2 nuclei unite the process is called karyogamy and a zygote is formed

Question 33

Meiosis

Answer 33

- has to take place before spore forming structures are able to produce spores, which would give rise to a new hypha and mycelium under ideal conditions - the spores contain 1 or several nuclei

Question 34

Aquatic and terrestrial fungi

Answer 34

- the spores of aquatic fungi often have flagella, while terrestrial fungi produce spores with thick resistant cell walls

Question 35

The most convenient way of classifying fungal diseases is to

Answer 35

- categorize them according to the type of infection that occurs

Question 36

Superficial infections of the skin and its appendages (nails, hair)

Answer 36

- these fungi are known as dermatophytes - consist of: 4 species of Microsporum, 8 species of Trichophyton and Keratinomyces ajelloi - most of these are commonly called ringworms, piedra, athletes foot

Question 37

Microsporum audouini

Answer 37

- tinea corporis (fungal infection of the body) - tinea capitis (fungal infection of scalp)

Question 38

Microsporum canis (transferred from animals)

Answer 38

- tinea corporis - tinea capitis

Question 39

Trichophytum rubrum

Answer 39

- tinea pedis (athletes foot) - tinea corporis - tinea cruris (fungal infection of groin) - paronychia (infection of the nailbed) - tinea unguium (infection of the nail plate)

Question 40

Trichophytum interdigitale

Answer 40

- tinea pedis - tinea cruris - tinea manuum (infection of hands) - tinea unguium

Question 41

Trichophytum schoenleini

Answer 41

- tinea capitis

Question 42

Trichophytum tonsurans

Answer 42

- tinea capitis - tinea unguium

Question 43

Trichophytum verrucosum

Answer 43

- tinea capitis

Question 44

Epidermophyton floccosum

Answer 44

- tinea pedis - tinea cruris - tinea manuum - tinea unguium

Question 45

Sporothrix schenkii

Answer 45

- sporotrichosis (tropical fungal infection affecting mostly men)

Question 46

Candidas albicans (yeast and yeast like fungi)

Answer 46

- candidiasis (superficial infection of body folds and mucous membranes) - very prominent in Immuno-deficiency diseases - thrush of the mouth and throat - vaginitis (thrush of the vagina)

Question 47

Malassezia furfur Pityrosporum ovale (yeast and yeast like fungi)

Answer 47

- tinea vesicolor - seborrheic dermatitis (scaly skin infection)

Question 48

Systemic infections or deep-seated mycoses

Answer 48

- occur deep within the tissues, involving vital organs and/or the nervous system - these infections may be chronic or fatal - candidas albicans (in the gastro-intestinal tract) - histop/asma capsu/atum (causes histoplasmosis, a fungal infection of the lungs) - coccidioides immitis (causes respiratory disease) - blastomyces dermatitidis (causes blastomycosis in the skin , viscera which is internal organs and bones