Unit 3.4 - microbiology

Question 1

Classification by shape

Question 2

Bacillus (rod shaped)

Answer 2

Escherichia coli
Bacillus

Question 3

Coccus(spherical)

Answer 3

Staphylcoccus
Streptococcus

Question 4

Sprial (corkscrew)

Answer 4

Spirillium

Question 5

Single

Answer 5

helicobacter

Question 6

Pairs

Answer 6

diplococcus
pneumonide

Question 7

chains

Answer 7

streptococcus

Question 8

clusters

Answer 8

staphylococcus

Question 9

what is gram staining?

Answer 9

method of staining the cell wall of bacteria to aid identification

Question 10

who invented the stain?

Answer 10

Hans gram

Question 11

who invented the petri dish?

Answer 11

Julian Petri

Question 12

who made the agar jelly?

Answer 12

Fanny hesse

Question 13

what does Gram stain allow?

Answer 13

it allows microbiologists to distinguish between Gram positive and Gram negative bacteria

Question 14

how is staining different?

Answer 14

if the chemical composition of the wall is different

Question 15

Process of staining Bacteria?

Answer 15

before staining, all bacteria are colourless
all the bacteria are treated with: crystal violet * a dye which binds to peptidoglycan in the cell wall and all the bacteria go purple
all the bacteria are treated with lugol’s iodine * a mordant which fixes the stain to the cell
only the gram positive remain purple and the gram negative doesn’t remain purple
ass acetone * alcohol to the gram negative ( decolouriser) which removes any crystal violet
gram negative became colourless
to the negative bacteria, ass sofranin (counter stain)
this turns the gram negative bacteria red

Question 16

Features of a Gram positive

Answer 16

have a thick outer wall (8nm) - made of peptidoglycen/murein same thing
there is no outer lipo polyachride layer - aiming to return the dye
lipids = non polar
dye = crystal violet and therefore non soluble - stains the cells purple

Question 17

What are examples of gram positives

Answer 17

Bacillus
Staphylococcus
Streptococcus

Question 18

What do Gram positives do?

Answer 18

they are susceptible to pencillin
they’re killed by the enzyme lysozyme as the enzyme hydrolyses the bonds holding the peptidoglycen molecules (lysosyme is found in saliva and human tears)

Question 19

What does Pencillin do?

Answer 19

They make their cell walls weak and therefore collapsable and Osmosis makes them burst