Lab 2

Question 1

Which two broad groups are fungi divided into?

Answer 1

Yeasts (essentially unicellular) and moulds (multicellular)

Question 2

Which two broad groups are fungi divided into?

Answer 2

Yeasts (essentially unicellular) and moulds (multicellular)

Question 3

What kind of pathogens are fungi?

Answer 3

opportunist pathogens

Question 4

What sort of conditions do fungal spores readily proliferate in?

Answer 4

Warm, moist conditions like Auckland

Question 5

In order to visualse moulds microscopically, they can be stained with what?

Answer 5

lactophenol blue or light green

Question 6

Yeasts take up gram stain reagents, but cannot be described as… what? why is this?

Answer 6

gram positive or gram negative

this is because they are not bacteria, and their cell wall is different from bacteria

Question 7

How can yeasts be easily distinguised from bacteria?

Answer 7

easily distinguished by size

Yeasts are eukaryotic and eukaryotic cells are generally bigger than prokaryotic cells (bacteria)

Question 8

What does candida albicans look like when grown on SDA?

Answer 8

spherical cells similar to cocci (except they are bigger)

Question 9

What happens after c. albicans growth in serum broth?

Answer 9

it undergoes a budding process and the buds eventually develop into long, thin extensions of the cell

Question 10

What are these long and thin extensions of thecell called?

Answer 10

pseudohyphae. This is to distinguish them from the real multicellular hyphae of moulds

Question 11

What are the main mode of vegetative growth for moulds?

Answer 11

The formation of long, branching filamentous structures (hyphae)

Question 12

What do moulds produce for reproduction?

Answer 12

they form conidiophores (fruiting bodies) which contain the small round conidia (spores)

Question 13

what is the diagnostic feature of candida albicans grown in serum broth?

Answer 13

long and thin extensions from the cell known as pseudohyphae
this results from a budding process in the serum broth

Question 14

What is SDA?

Answer 14

Sabouraud Dextrose Agar

Question 15

give an example of a genus of bacteria which do not stain readily by gram stain

Answer 15

mycobacterium

Question 16

How are these bacteria stained?

Answer 16

Staining of these organisms is facilitated by the application of heat

once stained, they retain dyes and resist decolourisation with acid or acid alochol

thus they are known as acid fast organims

Question 17

After staining, what do acid fast organisms look like?

Answer 17

they are NOT decolourised,

they retain the carbol fuchsin primary stain and appear RED

Question 18

after staining, what do non-acid fast organisms look like?

Answer 18

These are DECOLOURISED

They accept the counterstain methylene blue and appear BLUE

Question 19

What kind of pathogens are fungi?

Answer 19

opportunist pathogens

Question 20

What sort of conditions do fungal spores readily proliferate in?

Answer 20

Warm, moist conditions like Auckland

Question 21

In order to visualse moulds microscopically, they can be stained with what?

Answer 21

lactophenol blue or light green

Question 22

Yeasts take up gram stain reagents, but cannot be described as… what? why is this?

Answer 22

gram positive or gram negative

this is because they are not bacteria, and their cell wall is different from bacteria

Question 23

How can yeasts be easily distinguised from bacteria?

Answer 23

easily distinguished by size

Yeasts are eukaryotic and eukaryotic cells are generally bigger than prokaryotic cells (bacteria)

Question 24

What does candida albicans look like when grown on SDA?

Answer 24

spherical cells similar to cocci (except they are bigger)

Question 25

What happens after c. albicans growth in serum broth?

Answer 25

it undergoes a budding process and the buds eventually develop into long, thin extensions of the cell

Question 26

What are these long and thin extensions of thecell called?

Answer 26

pseudohyphae. This is to distinguish them from the real multicellular hyphae of moulds

Question 27

What are the main mode of vegetative growth for moulds?

Answer 27

The formation of long, branching filamentous structures (hyphae)

Question 28

What do moulds produce for reproduction?

Answer 28

they form conidiophores (fruiting bodies) which contain the small round conidia (spores)

Question 29

what is the diagnostic feature of candida albicans grown in serum broth?

Answer 29

long and thin extensions from the cell known as pseudohyphae
this results from a budding process in the serum broth

Question 30

What is SDA?

Answer 30

Sabouraud Dextrose Agar

Question 31

give an example of a genus of bacteria which do not stain readily by gram stain

Answer 31

mycobacterium

Question 32

How are these bacteria stained?

Answer 32

Staining of these organisms is facilitated by the application of heat

once stained, they retain dyes and resist decolourisation with acid or acid alochol

thus they are known as acid fast organims

Question 33

After staining, what do acid fast organisms look like?

Answer 33

they are NOT decolourised,

they retain the carbol fuchsin primary stain and appear RED

Question 34

after staining, what do non-acid fast organisms look like?

Answer 34

These are DECOLOURISED

They accept the counterstain methylene blue and appear BLUE

Question 35

describe the method of the zihl-neelsen staining procedure

Answer 35

1. Fixed slide is flooded with carbol fuchsin and heated to steaming for 5 mins.
   Stain must not dry out due to heat
   at this stage both types of cells will appear red
2. Slide is washed with tap water, and cells are decolourised with acid-alcohol drop by drop until the deep red appearance of the slide is reduced to pink. this takes 10-30sec
   * acid fast cells retain the stain and will look pink, microscopically
   * non acid fast cells unable to withstand treatment with acid alcohol, this results in leeching of red carbol fuschin from cell wall. They will appear colourless at this stage
3. Methylene blue - counter stain is applied (2 mins) this is not taken up by acid fast cells, but the blue counter stain is absorbed by non acid fast cells.
4. Slide is washed, then blotted dry.

Question 36

what accounts for the acid fast property of the mycobacterium species?

Answer 36

Mycobacterium have a thick cell wall, but no cell membrane so do not take up gram stain….. ?