microbiology

Question 1

what shape are bacillus bacteria?

Answer 1

rod shaped

Question 2

what shape are coccus bacteria?

Answer 2

spherical

Question 3

what shape are spirillum bacteria?

Answer 3

spiral

Question 4

what is the structure of bacteria?

Answer 4

circular DNA and plasmids
70s ribosomes
peptidoglycan cell wall
flagellum
pilus
capsule

Question 5

how are prokaryotes different to eukaryotes?

Answer 5

no membrane bound nucleus or organelles
70s ribosomes
peptidoglycan cell wall

Question 6

what does the cell wall do?

Answer 6

prevents osmotic lysis
rigidity
cell structure

Question 7

what is the structure of gram positive bacteria?

Answer 7

thick layer of peptidoglycan that holds dye

Question 8

what colour does gram positive bacteria stain?

Answer 8

purple
crystal violet dye is not washed out by ethanol

Question 9

what drug is effective against gram positive bacteria?

Answer 9

penicillin

Question 10

what is the structure of gram negative bacteria?

Answer 10

thin layer of peptidoglycan
outer layer of lipopolysaccharide
doesn’t hold dye

Question 11

what colour does gram negative bacteria stain?

Answer 11

pink
crystal violet dye is washed out by ethanol

Question 12

what are the metabolic requirements for microbes?

Answer 12

suitable temperature and pH
oxygen requirements
carbon, nitrogen and inorganic ions

Question 13

what is the optimum temperature for pathogens to grow at?

Answer 13

37 degrees

Question 14

what is optimum temperature for saprotrophs?

Answer 14

lower than 37 degrees

Question 15

what is optimum temperature for psychrophiles?

Answer 15

down to -15 degrees

Question 16

what is optimum temperature for thermophiles?

Answer 16

up to 80 degrees

Question 17

what are usual incubation conditions?

Answer 17

25 degrees
24-48 hours
aerobic conditions

Question 18

what are obligate aerobes?

Answer 18

bacteria which require oxygen

Question 19

what are obligate anaerobes?

Answer 19

can only grow in absence of oxygen

Question 20

what are facultative anaerobes?

Answer 20

able to survive in absence of oxygen but grow and divide faster in presence of oxygen

Question 21

what does aseptic technique do?

Answer 21

prevents contamination of environment by microbes being handled
prevents contamination of microbial cultures by unwanted microbes from environment

Question 22

what are examples of aseptic technique?

Answer 22

autoglave glassware
flaming loops, wires and glass spreaders
open petri dish at small angle
roaring blue flame to create convection current
flame neck of bottle

Question 23

what are streak plates used for?

Answer 23

use to separate mixed cultures into pure ones

Question 24

what are the problems with counting bacteria and solutions?

Answer 24

small - use microscope
lots of them - dilute sample
alive or dead? - allow them to grow into colonies

Question 25

what does total cell count include?

Answer 25

living and dead cells

Question 26

what does viable cell count include?

Answer 26

only living cells

Question 27

what are disadvantages of doing serial dilution to count bacteria?

Answer 27

possible to underestimate population due to clumping takes a long time to count

Question 27

what are advantages of doing serial dilution to count bacteria?

Answer 27

counts living cells