Microbial Techniques

Question 1

How do you culture microorganisms

Answer 1

1) transfer bacteria into an agar plate using an inoculating loop
2) close and seal then incubate

Question 2

4 phases of a bacterial growth curve

Answer 2

Lag phase
Log phase
Stationary phase
Death phase

Question 3

Explain what happens during the lag phase

Answer 3

1). Bacteria is newly introduced to an environment
2) slowly adapting to neutering medium
3) interphase occurs and the rna is replicated

Question 4

Explain what happens during the log phase

Answer 4

It’s when the bacteria start to grow and reproduce exponential growth
Binary fission occurs the growth rate doubles each time and exceeds the death rate
There is no limiting facts

Question 5

Explain what happens during the stationary phase

Answer 5

When the growth rate is equal to the death rate so therefore the population growth just stays stationary it staibilises at its maximum

Question 6

What happens during the death phase

Answer 6

This is when the death phase increases as a greater rate the. The growth phase there is an increase in toxic from death bacteria as well as lack of the nutrient medium as a result

Question 7

How would you conduct. Cell count

Answer 7

Dilute broth sample with equal volume of trypan
Use a calibrated haemocytimeter with a volume of 0.1 count the cells in each of the sets of squares and calculate mean.
3) number of bacterial cells = number of counted x 10^4 per cm^3

Question 8

Explain the process of using a haemocytometer

Answer 8

1) the number given to a counting chamber designed to count the number of cells
Each has a central platform and a bride attached to count the cellls

Question 9

What are the positives and negatives of using a haemocyometer

Answer 9

Pros
It gives an accurate and exact number of cells and it tell you exactly how many viable cells there are

Cons
It’s a very slow process and sometimes it can be expensive

Question 10

Explain how turbidity works

Answer 10

Place a sample into. A curvette
Place into a colurimeter and pass light through ,ensuring either the transition or the absorbance
The greater the amount of bacteria there is a greater absorbance and a lower transmission

Question 11

The positives and negatives about turbidity

Answer 11

Pros
It’s a very fast and easy process and gives a number of total cells
Cons
It doesn’t give an exact value of cell count

Question 12

Explain how a spread plate works

Answer 12

Spread the sample of bad tears evenly over a spread dish and d count the number of cells that grow

Question 13

What are the positives and negatives of spread plate

Answer 13

Pros
They give an exact number of cells and count the amount of living cells
cons
Very slow and expensive as you have to wait for bacteria to grow and culture to be able to see accurate results

Question 14

Explain what the process of dry mass

Answer 14

1) weight the sample
Find the mass of sterile filter membrane
Filter the bacteria from broth culture
Heat the bacteria and filter membrane to 100
Until mass remains constant
Record the mass

Question 15

What are the pros and cons of dry mass

Answer 15

Pros
Counts the number of living and dead cells
And is very fast
Cons
It’s not as accurate compared to other dilution and optical methods

Question 16

What is a bactericidal antibiotic example penecilin

Answer 16

Bactericidal kills the bacteria and prevent the cell wall building
Penecilin in most effective against gram positive bacteria that heavily rely on cell wall
Penecilin inhibits the enzyme transpeptise which cross links chains in the cell without this the cell wall breaks
And can no longer withstand the turner pressure and causes cell to burst

Question 17

What is bacteriostatic and an example tetracycline

Answer 17

Bacteriostativ prevents the growth repair and reproduction of bacteria but it doesn’t kill it lets the immune system kill the badcteirs on its own
Example tetracycline
Binds to the 70s ribosomes and prevents protein synthesis
Thus prevents proteins being produced and therefore cell replication and growth this is medical.y very useful

Tetracycline is very effective in inhibiting broad spectrum bacteria