microbial growth

Question 1

what happens at the cellular level of binary fission

Answer 1

each bacterium reproduces by binary fission splits into two

Question 2

what is binary fission

Answer 2

asexual reproduction by a separation of the body into two new bodies

Question 3

What is microbial growth

Answer 3

An increase in the number of cells.

Question 4

How to control microbial growth

Answer 4

Yoghurt

Anaerobic digested in wastewater treatment

Question 5

Describe the growth by binary fission

Answer 5

At cellular level each bacterium reproduces by binary fission (splits in two).
The cells elongate to up to twice its length e.g E coli before forming a partition to seperate into two daughter cells.
Partition is called a septum. This results from growth of cytoplasmic membrane and cell wall.
1) cell elongated and dna is replicated
2) cell wall and plasma membrane begin to grow inward
3) cross wall forms completely around divided dna
4) cells separate

Question 6

What is the time takes for one cell to become two in binary fission called

Answer 6

Generation time

Question 7

How can an unbalanced growth occur in binary fission of the cells

Answer 7

Change in environment and nutritional conditions

This may lead to death of the culture

Question 8

Describe the genetic mechanisms

Answer 8

• Fts proteins for the divisome
• polymerisation of ftsZ results in the building of a ring around the centre of the cell
• ZipA helps to anchor the ring to tbe cytoplasmic membrane
• Ftsl is involved in peptidoglycan synthesis
• FtsK helps chromosome separation

Question 9

Describe the control of the divisome

Answer 9

• MreB proteins give shape to the bacteria
• MinC, D and E proteins spirals through the cell and stops the FtsZ ring by oscillating
• once the cell grows the Min proteins are stretched
• they no longer prevent FtsZ ring from forming

Question 10

What is peptidoglycan made up from

Answer 10

Made up from NAM and NAG with a transpeptide on NAM

Question 11

How is the new wall peptidoglycan built

Answer 11

Autolysins cut out the cell walls at the FtsZ ring.
Bactoprenol then transports new NAM-NAG across the cell membrane.
Glycolases then catalyse the bonding of new peptidoglycan.

Question 12

How does peptidoglycan synthesis work

Answer 12

….

Question 13

What is the time taken to get from one cell to two called

Answer 13

Generation time

Question 14

What is exponential growth

Answer 14

Cell numbers get large very quickly
The number of cells can be calculated as 2n
N=N02n

Question 15

How to calculate number of generations example
Bacteria time =0 and using serial dilutions calculate total number of cells to be 5000
After 6 hours we plate out the suspension again and find that there are 30000 cells

Answer 15

30000= 5000 x 2n
2n=6
Log10 2n =log10 6 
n x 0.301=0.778
n = 0.778/0.301
n = 2.6

Question 16

Another example of generations

Culture starts with 7000 how many cells will there be after 8 generations

Answer 16

N= N02n
N=7000x 2^8
N= 7000 * 256
N=1792000 or 1.8x10^6

Question 17

How to calculate generation time

Answer 17

Generation time = time / number of generations

G=t/n

Question 18

What is growth rate

Answer 18

Change in cell number per unit time
Defined as u (mu)
Number of cells N=e^ut
N=No x e^u (t-t0)

Question 19

Why is it important to know growth kinetics

Answer 19

So we can replicate experiments with the exact same or proportional number of cells.
If u wanted to obtain particular conc of cells you woukd know how long to culture e.g 2 hours in the calculation.
In industrial setting wastewater treatment, number of microorganisms and growth kinetics determine how quick or.slow waste sources can be introduced.
Non sterilised food.products help determine shelf life

Question 20

What are the two important factors about continuous culture

Answer 20

• dilution rate- how quickly you pump fresh media in and spent media out
• concentration of a limiting nutrient

Question 21

Describe chemostat in continuous culture

Answer 21

….

Question 22

What is dilution rate

Answer 22

Is the flow e.g. 500ml/h divided by the volume in the vessel e.g. 1000ml so 0.5ml/h .
Wide range of dilution rates allow for a steady state of growth.
If dilution rate is too slow then tbe cells begin to die of starvation increasing the doubling time.
If dilution rate is too fast the organism cannot grow fast enough to stop itself being diluted and washed out of the system.

Question 23

What happens when the dilution rate is too slow

Answer 23

Not enough food being introduced, so population cannot increase.
Some product produced but not usable concentration.

Question 24

Whag happens if dilutions is too fast

Answer 24

Population can increase however the new cells are lost to effluent

Question 25

What happens if the dilution is just right

Answer 25

Population can increase, kept at a steady state by loss of cells to effluent. All substrate converted to product

Question 26

What happens at low concentrations of nutrient

Answer 26

The growth rate is sub maximal because the cells cannot get the nutrients in the cell to meet metabolic demand

Question 27

What happens when there is a hugh concentration of nutrient

Answer 27

The growth rate plateaus since there is a competition for space. Yield will continue to rise however to a fixed limit ( solubility, enzymatic)

Question 28

Describe the wastewater treatment

Answer 28

The waste water entering sewage cannot be discharged to the environment because of -publix health consideration -environmental consideration -aesthetics Wastewater treatment uses a number of processes to remove and neutralise contaminants (^the above will be explained in a series of steps)

Question 29

What is the primary treatment for wastewater treatment

Answer 29

- physical barrier - series of gates which seperate large objects - left with two outputs for solid and liquids - liquid component still contains large concentration of both bacteria and food - soluble organic material

Question 30

Describe the secondary treatment- (aerobic) for wastewater treatment

Answer 30

The liquid component is added to an aeration tank. The organic components on the tank are eaten by microorganisms. Microorganisms form flocks which are mix of organism and biofilm, heavy, kept suspended by aeration and settle in effluent.

Question 31

What is the tertiary treatment for wastewater treatment

Answer 31

Some of the organisms are removed from the settling tank. The remaining effluent can then be discharged to rivers and streams. Rest can be sent for water treatment which is usually sedimentation and coordination Then drinking water !!!!

Question 32

Secondary digestion - anoxic

Answer 32

Solid material although separated cannot be simply allowed to pile up We eag lots of fibre which are insoluble and also a good food source for bugs. Polysacharides are broken down to smaller substrates These can then be converted to methane- biogas

Question 33

What are uses of anoxic secondary digestion

Answer 33

Production of insulin Continuous culture In exponential growth substrate is consumed and the product is insulin not from the substrate produced from growth

Question 34

Why a batch culture?

Answer 34

Continuous culture has one flaw | One substrate in and one product out e.g insulin production/ wastewater and substrate is repaired to co2

Question 35

Describe the stages of microbial growth cycle and draw a graph to show these stages

Answer 35

Lag phase Log (exponential) phase Stationary phase Death ( decline) phase

Question 36

Describe the lag phase in the microbial growth cycle

Answer 36

No population increase Microbes synthesizing cell parts and enzymes Microbes are adapting to new environment Varies in length In some cases can be very short or even absent for instance when sub cultures from an exponential culture. Can be long when moving from a complex to a defined medium, biosynthesis of different enzymes.

Question 37

Describe the logarithmic (exponential) phase

Answer 37

``` Population increasing at maximum rate Growth curve rises smoothly Population doubles at regular intervals ( generation time) Liquid media become turbid Colonies appear on solid media ```

Question 38

Describe the stationary phase in microbial growth cycle

Answer 38

``` Many microbes dying Number of dead balances number of new Nutrients scarce Waste builds up Curve flattens ```

Question 39

What are the possible reasons for entry into stationary phase

Answer 39

Nutrient limitation Limited oxygen available Toxic waste accumulation Critical population density reached

Question 40

What are the starvation responses

Answer 40

Morphological changes e.g. endospore formation Decrease in size, protoplast shrinkage and nucleoid condensation Production of starvation proteins Long term survival Increased virulence

Question 41

How are bacterial endospore formed

Answer 41

Certain species of bacteria form endospores during the process of sporulation Spores are resistant to heat , harsh chemicals, radiation or starvation Regarded as a dormant stage ( vegetative cell - endosprore- vegetative cell )

Question 42

Describe the death phase in microbial growth

Answer 42

Microbes dying rapidly Death phase also an exponential function Occasionally cells lyse Capsules/ slime layers may buffer cells against environment Spores may form

Question 43

If there a use for the death phase in microbial growth cycles

Answer 43

Production of penicillin As a starvation response penecillium produces antibiotic. Would not get this is in continuous culture as sugar would not be depleted

Question 44

What is used in alcohol production

Answer 44

``` Yeast not bacteria but same principle apples Add sachharomyces to Grapes - wine Makt/make hops-beer Apples - cider ```

Question 45

How is Vinegar produced

Answer 45

Conversion of ethyl alcohol to acetic acid E.g. wine beer fermented rice or cier can be used Aceti acids vinegar Acetobacter and gluconobacter are key genera

Question 46

How is Yorgurt produced

Answer 46

Yoghurt production Pasteurise the milk and add lactobacillus bulgaricus and streptococcus thermophilus Converts lactose to lactic acid Monitor the pH to 4.5 Stop the fermentation by booking to 7 degrees

Question 47

How is kombucha produced - mixed batch culture

Answer 47

Traditional health drink Fermentation of sugary tea Charachterised by a symbiotic communities of bacteria and yeasts (scoby) Sugar is converted to alcohol by first set of microbes Alcohol is then converted to acetic acid by secondary set of microbes

Question 48

Overview of the batch

Answer 48

Easy to set up and maintain If contamination occurs only one batch is lost Useful for production of secondary metabolites but growth rate is slower because of reducing nutrient levels. Less efficient because it is not constantly in operation

Question 49

Overview of continuous

Answer 49

Growth rate is higher because of constant nutrient addition More efficient as constantly operational More useful for primary metabolites More difficult to set up but if contaminated lots of product lost