FUNGI

Question 1

CLASSIFICATION OF THE TYPES OF MICROORGANISMS

Answer 1

• BACTERIA - UNICELLULAR (BACTERIOLOGY)
• FUNGI (YEASTS AND MOULDS) -UNICELLULAR OR MULTICELLULAR (MYCOLOGY)
• PROTOZOA (UNICELLULAR) - protozoology
• HELMINTHS MULTICELLULAR
• VIRUSES - NONCELLULAR - virology
• PRIONS - NON CELLULAR (mad cow disease, BSE, Creutzfeldt-Jakob disease)

Question 2

classification of FUNGI

Answer 2

• MICROSCOPIC: unicellular (yeast), multicellular (mould)

- MACROSCOPIC: mushrooms, toadstools

Question 3

mycology definition

Answer 3

=study of fungi

Question 4

How many fungal species are there?

Answer 4

90,000 fungal species and 50 cause human diseases - mycoses

Question 5

Properties of fungi

Answer 5

• eukaryotic
• spore-bearing
• absorptive nutrition
• no chlorophyll
• reproduce sexually and asexually
• cell wall made of chitin (POLYSACCHARIDE)
• BODY OR VEGETATIVE STRUCTURE IS THALLUS

Question 6

SAPROPHYTES - DEFINITION

Answer 6

-LIVE ON DEAD PLANT AND ANIMAL MATERIAL

Question 7

PARASITE - DEFINTION

Answer 7

LIVE IN/ON LIVING MATERIAL

Question 8

DESCRIBE FUNGAL METABOLISM

Answer 8

• AEROBIC (GENERATE ATP FROM GLYCOLYSIS)
• FACULTATIVE ANAEROBES - FERMENTATION (MAKE ETHYL ALCOHOL FROM GLUCOSE)
• OBLIGATE ANAEROBES (RUMEN OF CATTLE)

Question 9

EXAMPLE OF FUNGI

Answer 9

-YEASTS ( saccharomyces cerevisiae) - mean generation time = 2 hours; candida albicans

Question 10

structure of fungi

Answer 10

• nuclear membrane
• nucleus
• mitochondria
• vacuole
• bud
• capsule
• cell wall made of chitin
• cytoplasmic membrane (ergosterol is a unique sterol in the fungal membrane)

Question 11

Structure of chitin

Answer 11

• a natural polymer of N-acetyl glucosamine (NHCOCH3)
• absent in mammalian cells
• target for antifungal chemotherapy (eg caspofungin)

Question 12

structure of ergosterol

Answer 12

• unique sterol in fungal cell membrane
• 4 rings fused together
• synthesis of ergosterol for incorporation into the plasma membrane
• makes the plasma membrane sensitive to antimicrobial agents which either block the synthesis of ergosterol or prevent its incorporation into the membrane or bind to it (azole, polyene antifungals)

Question 13

reproduction in fungi

Answer 13

• sexual and asexual
• Diploid yeast cell leads to budding, in plentiful of food supply which then produces daughter diploid cells (identical to mother cells, no genetic diversity)
• Diploid yeast cell forms 4 haploid mould cells with outer coats enclosed in outer cell which then fuse to create 1 cell (increases genetic diversity and chance of survival)

Question 14

MOULD - structure

Answer 14

• long and branched thread-like filaments of cells (hyphae)
• hyphae form mycelium
• hyphae can be continuous or crossed walled -septa
• they have a distinct spore structure which helps with identification
• one single spore produces one new colony (enumeration)

Question 15

Treatment for fungal diseases describe general problems

Answer 15

• Fungi are eukaryotes and are therefore more difficult to treat (high similarity to humans)
• Drugs tend to be more toxic
• repeated applications needed
• lengthy treatments

Question 16

ANTIFUNGAL DRUG targets

Answer 16

• Proteins (enzymes) involved in fungal membrane synthesis (ergosterol), enzyme chitin synthase (cell wall), beta-(1,3) D-glucan synthase (cell wall)
• Membrane - drugs that interact with membrane sterols