unit6 :principles of bacterial nutrition

Question 1

why should bacterial food be in solution

Answer 1

because it uses osmosis to pass through the cell wall and semi-permeable membrane

Question 2

what affects bacterial cell population and growth when they are in a confined environment as compared to when they are in their normal nature

Answer 2

there is accumulation of waste products and depletion of nutrients when bacteria is in a test tube or agar plate

Question 3

what does bacteria use to break down substances

Answer 3

enzymes which it secretes

Question 4

differentiate between the 2 types of enzymes that bacteria uses to hydrolyse substances

Answer 4

1.exo-enzymes- pass outward from the cell
2.endo-enzymes : part of the cell itself or functions within the cell

Question 5

what helps enzymes to function better

Answer 5

coenzymes

Question 6

differentiate between constitutive and inducible enzymes

Answer 6

constitutive enzymes- synthesized irrespective of their environmental conditions and
inducible enzymes- synthesized only in the presence of their substrate

Question 7

what are the 3 examples of enzymes

Answer 7

oxido-reductases

hydrolases

transferases

Question 8

what is oxidation and how does oxidation state increase

Answer 8

oxidation is the loss of electron and this increases the oxidation state

Question 9

which of the 3 enzyme examples catalyzes oxidation-reduction reactions

Answer 9

oxido-reductases

Question 10

what does the enzyme hydrolases do

Answer 10

catalyzes hydrolysis of compounds

Question 11

what does transferases do

Answer 11

catalyses transfer of chemical groups from1 compound to another

Question 12

define catabolism

Answer 12

breakdown of molecules to obtain energy

Question 13

what is the difference between reduction and oxidation

Answer 13

oxidation- loss of electrons
reduction- gain of electrons

Question 14

does the oxidation number increase or decrease with a gain of electrons

Answer 14

it decreases because we are becoming more negative

Question 15

what is oxidative phosphorylation

Answer 15

transfer of energy-rich phosphate bonds to ADP to form ATP through electron transport system

Question 16

in the presence of oxygen( which acts as an electron acceptor) bacteria produce 2 toxic products what are they.
what is used by anaerobic bacteria which do not have oxygen

Answer 16

superoxides and peroxides

anaerobic bacteria use nitrate

Question 17

what is termed the process in which energy is produced during passage of electrons from substrate to an inorganic electron acceptor.

and what are the waste products produced

Answer 17

fermentation

acid, alcohol and gas

Question 18

how often does bacteria multiply

Answer 18

every 20min

Question 19

what is the difference between Total count growth curve and viable count growth curve

Answer 19

total count - incl. both viable and non viable cells

viable count- incl. viable cells only

Question 20

draw and label a total count growth curve

Answer 20

answer on notebook

Question 21

what is the difference between a total count growth curve and a viable count growth curve

Answer 21

the viable count growth curve doesnt have a death phase cause it only measures the viable cells.

Question 22

in 2 points describe what happens in lag phase

Answer 22

1. no multiplication
2. organisms still adapting to growth in a new medium

Question 23

what is happening in log phase

Answer 23

cells divide at constant rate and theres high metabolism to maintain high rate of division

Question 24

what are the 2 main ingredients of basal agar

Answer 24

hydrolysate of protein
2.source of growth factors and inorganic salts

Question 25

list the 5types of media

Answer 25

1. basal media
   2.selective media
   3.enriched media
   4.indicator media
   5.enrichment media

Question 26

what are the 3 nutrients of nutrient agar

Answer 26

peptone, beef extract and agar

Question 27

what grows on Nutrient agar and what colour does it produce

Answer 27

pseudomonas aerginosa
produces a green pigment (pyocanin)

Question 28

what type of media is blood agar

Answer 28

enriched medium- 5-10% sheep or horse blood which contains X-factor (haemin) from the blood

Question 29

what are the 3 types of hemolysis in blood agar

Answer 29

alpha, beta and delta

Question 30

how do we know if its alpha hemolysis in blood agar

Answer 30

green tint around colonies

Question 31

difference between beta and delta hemolysis in blood agar and expected colour

Answer 31

beta- complete clearing around colonies (yellow)
delta- no change (white/grey)

Question 32

what type of media is chocolate agar and what factors does it contain and what colour is it

Answer 32

enriched media
both X factor (hemin) $ V factor (respiratory co-enzyme)

its brown-chocolate in colour

Question 33

what type of media is MacConkey agar

Answer 33

selective and differential culture media

Question 34

what type of bacteria is cultivated by MacConkey agar

Answer 34

Gram-negative

Question 35

what are the main 5 ingredients in MacConkey agar

Answer 35

1. crystal violet
   2.bile salts
   3.lactose
   4.neutral red
   5.NaCl

Question 36

of the 5 Ingredients of MacConkey agar, which one(s)
-inhibit gram+ bacteria
-distinguish lactose fermenting bacteria and non-lactose fermenting bacteria
-prevents spreadind of Proteus colonies

Answer 36

-crystal violet & bile salts
-lactose & neutral red
-NaCl

Question 37

if lactose is fermented will the pH drop or increase and what colour change is expected

Answer 37

pH drops and neutral red to pink colour change is expected

Question 38

what is used for the ones that cannot ferment lactose, the pH and colour change

Answer 38

peptone is used which produces alkaline ammonia and colourless/yellow colour change is expected

Question 39

which lactose fermenter produces mucous (moist & sticky) like colonies

Answer 39

klebsiella

Question 40

what type of media is mannitol salt agar

Answer 40

selective & differential media

Question 41

what is the principle of mannitol salt agar

Answer 41

if mannitol (sugar) is fermented pH drops and a yellow colour change is expected

non-mannitol fermenter remain reddish (from phenol red pH indicator) colonies.

Question 42

what type of media is deoxycholate citrate agar and which 2 species does it isolate

Answer 42

selective and differential agar

salmonella & shigella

Question 43

what is the principle for deoxycholate citrate agar

Answer 43

salmonella- pale with black center colonies
shigella- pale no black center