Microbiology

Question 1

bacteria shapes

Answer 1

cocchus (round)
bacillus (rod-shaped)
spirillum (spiral)

Question 2

gram staining cell wall

Answer 2

apply crystal violet, apply mordent stain (iodine), alcohol wash, apply safranin
Gram + = keeps violet stain even after alcohol wash
Gram - = red after alcohol wash + safranin

Question 3

gram + cell wall

Answer 3

basic
peptidoglycan + plasma membrane
affected by penicillin

Question 4

gram - cell wall

Answer 4

complex
lipopolysaccharide layer + peptidoglycan + plasma membrane
lipopolysaccharide layer removed by alcohol wash
not killed by penicillin

Question 5

how is bursting prevented

Answer 5

cross linking of polysaccharides and polypeptides make peptidoglycan (murein) providing strength and shape when cell takes in water by osmosis

Question 6

five basic techniques

Answer 6

innoculate
incubate
isolate
inspect
identify

Question 7

conditions for bacterial growth

Answer 7

water
nutrients in 'nutrient medium' (broth/agar)
Carbon + energy source (glucose)
nitrogen (for amino acids)
vitamins + mineral salts
optimum pH, temp
presence/absence of oxygen

Question 8

bacteria that grow well in aerobic conditions

Answer 8

obligate aerobe

facultative anaerobe

Question 9

bacteria that can grow in aerobic conditions but better in anaerobic conditions

Answer 9

obligate anaerobe

Question 10

pathogenic bacteria grow well in…

Answer 10

anaerobic conditions

37°C (body temp)

Question 11

aseptic technique

Answer 11

sterile technique
equipment + growth media sterilised using heat (autoclave at 121°C 15mins) or irradiation (gamma to sterilse plastic petri dishes)

Question 12

two types of bacteria counting methods

Answer 12

total cell count - number of living + dead bacterial cells

viable cell count - number of living bacterial cells

Question 13

viable cell count

Answer 13

known volume of liquid containing organisms added to agar plate, assume 1 cell gives rise to 1 colony
limitation - doesn’t take clumping into account (underestimate)

Question 14

serial dilution

Answer 14

when bacteria not in countable range
1cm3 of original culture to 9cm3 of sterile saline, 1cm3 to next 9cm3 and so on (keep diluting), 1cm3 of each diluted sample on agar plate at 25°C for 2 days (plating)