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worlds of microbes > microbial growth > Flashcards

microbial growth Flashcards

1
Q

what happens at the cellular level of binary fission

A

each bacterium reproduces by binary fission splits into two

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2
Q

what is binary fission

A

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

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3
Q

What is microbial growth

A

An increase in the number of cells.

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4
Q

How to control microbial growth

A

Yoghurt

Anaerobic digested in wastewater treatment

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5
Q

Describe the growth by binary fission

A

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

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6
Q

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

A

Generation time

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7
Q

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

A

Change in environment and nutritional conditions

This may lead to death of the culture

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8
Q

Describe the genetic mechanisms

A
  • 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
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9
Q

Describe the control of the divisome

A
  • 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
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10
Q

What is peptidoglycan made up from

A

Made up from NAM and NAG with a transpeptide on NAM

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11
Q

How is the new wall peptidoglycan built

A

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.

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12
Q

How does peptidoglycan synthesis work

A

….

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13
Q

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

A

Generation time

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14
Q

What is exponential growth

A

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

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15
Q

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

A 
30000= 5000 x 2n
2n=6
Log10 2n =log10 6 
n x 0.301=0.778
n = 0.778/0.301
n = 2.6
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16
Q

Another example of generations

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

A

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

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17
Q

How to calculate generation time

A

Generation time = time / number of generations

G=t/n

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18
Q

What is growth rate

A

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

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19
Q

Why is it important to know growth kinetics

A

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

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20
Q

What are the two important factors about continuous culture

A
  • dilution rate- how quickly you pump fresh media in and spent media out
  • concentration of a limiting nutrient
21
Q

Describe chemostat in continuous culture

A

….

22
Q

What is dilution rate

A

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.

23
Q

What happens when the dilution rate is too slow

A

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

24
Q

Whag happens if dilutions is too fast

A

Population can increase however the new cells are lost to effluent

25
Q

What happens if the dilution is just right

A

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

26
Q

What happens at low concentrations of nutrient

A

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

27
Q

What happens when there is a hugh concentration of nutrient

A

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

28
Q

Describe the wastewater treatment

A

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)

29
Q

What is the primary treatment for wastewater treatment

A
  • 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
30
Q

Describe the secondary treatment- (aerobic) for wastewater treatment

A

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.

31
Q

What is the tertiary treatment for wastewater treatment

A

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 !!!!

32
Q

Secondary digestion - anoxic

A

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

33
Q

What are uses of anoxic secondary digestion

A

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

34
Q

Why a batch culture?

A

Continuous culture has one flaw

One substrate in and one product out e.g insulin production/ wastewater and substrate is repaired to co2

35
Q

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

A

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

36
Q

Describe the lag phase in the microbial growth cycle

A

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.

37
Q

Describe the logarithmic (exponential) phase

A 
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
38
Q

Describe the stationary phase in microbial growth cycle

A 
Many microbes dying 
Number of dead balances number of new 
Nutrients scarce 
Waste builds up
Curve flattens
39
Q

What are the possible reasons for entry into stationary phase

A

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

40
Q

What are the starvation responses

A

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

41
Q

How are bacterial endospore formed

A

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 )

42
Q

Describe the death phase in microbial growth

A

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

43
Q

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

A

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

44
Q

What is used in alcohol production

A 
Yeast not bacteria but same principle apples 
Add sachharomyces to 
Grapes - wine 
Makt/make hops-beer 
Apples - cider
45
Q

How is Vinegar produced

A

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

46
Q

How is Yorgurt produced

A

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

47
Q

How is kombucha produced - mixed batch culture

A

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

48
Q

Overview of the batch

A

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

49
Q

Overview of continuous

A

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

worlds of microbes (5 decks)

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