L2 bacteria nutrition

Question 1

what are the two types of culture media

Answer 1

defined

complex

Question 2

what does a define culture media mean

Answer 2

chemically pure
know the exact composition and all components
SPECIFIC chemicals: amino acids, vitamins and specific sugars
ingredients added individually

Question 3

Define a complex culture media

Answer 3

not chemically pure
don’t know the exact composition
complex nutrient sources : glucose, beef and yeast extract, peptones

Question 4

what kind of media are specialised medias

Answer 4

complex

Question 5

what are the five types of specialised media

Answer 5

transport
enriched 
enrichment broth
selective
differential

Question 6

define a transport media

Answer 6

maintains all organisms without cell division
used for transporting from patient to lab
minimal growth nutrients only buffers and salts

Question 7

define enriched media

Answer 7

“generally encouraging”
general nutrient supplements, serum or yeast extract
for the fastidious organisms (fussy)
harvest as many microbes from unknown situation

Question 8

define enrichment broth

Answer 8

“specifically encouraging”
promotes the growth of one organism (competitive advantage)
holds rest in lag phase
Increases the number to DETECTABLE levels

Question 9

define enrichment broth

Answer 9

“specifically encouraging”
promotes the growth of one organism (competitive advantage)
holds rest in lag phase
Increases the number to DETECTABLE levels

Question 10

define selective media

Answer 10

“specifically inhibiting”
isolation and identification of specific microbes
general nutrients plus specific chemicals that inhibit specific microbes
mannitol salt agar : selective for staphylococci

Question 11

define differential media

Answer 11

preliminary identification of pathogens
changes colour due to biochemical reaction
mannitol salt agar: S.aurues ferments the mannitol carb resulting in an acid which changes the agar plate colour

Question 12

mannitol salt agar fermentation process (products)

Answer 12

Mannitol-> D-fructose -> D-fructose-6-phosphate -> pyruvic acid -> organic acid

Question 13

mannitol salt agar fermentation process (enzymes/reactions)

Answer 13

Mannitol dehydrogenase

fructokinase

glycolysis

fermentation

Question 14

what type of media are blood agar plates

Answer 14

enriched

differential

Question 15

How are blood agar considered
enriched?

differential?

Answer 15

they contain lots of nutrients for general encouragement of growth

they change colour due to bacterial enzymes causing haemolysis of the red blood cells

Question 16

what colouring shows alpha haemolysis on blood agar

Answer 16

green discolouration

Question 17

what colouring shows beta haemolysis on blood agar

Answer 17

completely clear

Question 18

what colouring shows gamma haemolysis on blood agar

Answer 18

non-haemolytic

Question 19

what are the stages of theoretical bacteria growth in a batch culture

Answer 19

lag 
exponential
stationary
death/decline
long term stationary phase

Question 20

what occurs during the long term stationary phase

Answer 20

genetically distinct bacteria are reproducing, the ones best able to use the nutrients

Question 21

bacteria growth equation

Answer 21

initial number x 2 ^ n

n = number of generations

Question 22

what kind of bacteria is E.coli
oxygen sensitivity?
where is it commonly found
role in normal microbiome
media requirements

Answer 22

gram-negative rod
facultative anaerobic
lower intestine of warm blooded animals
food diegestion and Vitamin K2 production (blood clotting)
not reliant on media as it produces all 20 EAA

Question 23

what is the name for an open system

Answer 23

continous culture

Question 24

how do continuous cultures work?

Answer 24

keeps microbes in exponential or stationary phase by supplying the bacteria with fresh nutrients and removing the toxins
the rate of growth is relative to the ingrediants

Question 25

what are continuous cultures used for?

Answer 25

when by-products of the bacteria need to be harvested

Question 26

what is the name of the equipment used for making a continuous culture

Answer 26

chemostat

Question 27

what are primary metabolites and when are they produced?

Answer 27

they are intermediate or end products of chemical reactions used for the growth of microbes
-amino acids/ nucleotides
produced during log/exponential phase

Question 28

what are secondary metabolites used for and when are they produced?

Answer 28

not essential for growth
accumulate in stationary phase
-antibiotics

Question 29

what ways can the population density be determined

Answer 29

direct: microscopic observation
direct: turbidity
viable: plate count

Question 30

what does microscopic observation involve?

Answer 30

sample put onto a slide

using a counting chamber on the slide the cells are viewed and counted directly

Question 31

what does using the turbidity to measure the pop. density involve

Answer 31

creating a standard curve of turbidity of the bacteria you are wanting to count
using a spectrometer to measure the turbidity of your sample
comparing your sample to the graph

Question 32

what does a plate count involve

Answer 32

the sample is diluted and spread onto a plate
each cell gives rise to a colony
colonies are counted

Question 33

why are direct methods advantageous

Answer 33

they are fast

Question 34

what are the disadvantages to direct methods of pop. density counts

Answer 34

they count both dead and alive cells

Question 35

advantages to viable cell counts

Answer 35

only counts alive cells, so it is more accurate

Question 36

disadvantages to viable cell counts

Answer 36

takes a long time

colonies show after 18-24 hours of incubation

Question 37

how is hektoen agar both differential and selective media

Answer 37

selective: contains bile salts that only some gram negative bacteria can grow in (E.coli)
differential: contains acid fuchsin and bromothymol blue which are pH indicators, so when the lactose, sucrose and salicin (carbs) are fermented it changes colour due to the acid production