microbiology

Question 1

how can bacteria be distinguished

Answer 1

size
shape
staining characteristics
metabolic/antigenic/genetic features

Question 2

what determines the shape of bacteria

Answer 2

the cell wall

Question 4

what is the structure of bacteria cell walls

Answer 4

3d mesh of peptidoglycan

Question 5

what is the structure of gram positive bacteria

Answer 5

thicker peptidoglycan wall
retains crystal violet stain when washed with alcohol so stains purple

Question 6

why do gram negative bacteria stain pink /red

Answer 6

when treated with alcohol, outer lipolysaccharide layer is lost so crystal violet washed off and then it gets stained red with safranin

Question 7

what conditions are needed for bacteria to grow

Answer 7

temperature
pH
nutrients
oxygen

Question 8

what are obligate aerobes

Answer 8

require oxygen for metabolism

Question 9

what are facultative anaerobes

Answer 9

can respire anaerobically if they need to

Question 9

what are obligate anaerobes

Answer 9

bacteria that can only survive in absence of oxygen

Question 9

what nutrients are normally supplied in nutrient media

Answer 9

carbon compounds e.g glucose
nitrogen
vitamins or mineral salts

Question 9

what is the difference between total cell count and viable cell count

Answer 9

viable count only counts living bacteria
total count counts all bacteria

Question 10

list some aseptic techniques

Answer 10

flame neck of culture vessels
flame the innoculating loop
sterilise work surface
only secure petri dish with two pieces of tape
do not incubate at 37 degrees
autoclave at 121 degrees for 15 minutes