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Microbiology > Lecture 4- Microbial growth > Flashcards

Lecture 4- Microbial growth Flashcards

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Biology 101 flashcards
1
Q

What is bacterial growth?

A

an increase in population size not an increase in the size of a single bacterium

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2
Q

How do bacterial cells replicate?

A

a form of asexual reproduction called binary fission

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3
Q

What is generation time?

A

time required to complete fission cycle from parent cell to 2 daughter cells. (Doubling time). It is the amount of time needed to double the population.

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4
Q

What is the growth rate? What does this vary depending on?

A

The measure of the length of the generation time environmental condictions

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5
Q

What is the generation time of Mycobacterium leprae?

A

10-30 days (leprosy)

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6
Q

What is the generation time of Staphylococcus aureus?

A

20-30 minutes

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7
Q

What 4 phases does a growth curve have?

A

Lag, Log or exponential, stationary and decline

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8
Q

What is a batch culture?

A

a closed-system microbial culture of fixed volume with limited supplies that aren’t replemished. Cells grown in a closed system have 4 phases: Lag phase, Log or exponential phase, stationary phase and death phase

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8
Q

What is the lag phase?

A

Interval of time between when a culture is inoculated and when growth begins. (not mutiplying as it is aclimitising)

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9
Q

What is the expontential phase?

A

Number of cells doubles during each unit of time.
During exponential growth, the increase in cell number is initially slow but increases at a faster rate

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10
Q

What is the stationary phase?

A

Growth rate of population is zero.
Number new divisions=number of cells dying
Either an essential nutrient is used up or waste product of the organism accumulates in the medium

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11
Q

What is the death phase?

A

Lack of nutrients and increasing accumulation of wastes lead to… number of cell deaths > number of new divisions

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12
Q

What is a continuos culture?

A

an open-system microbial culture of fixed volume

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13
Q

What is chemostat and turbidostat?

A

most common type of continuous culture device

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14
Q

What effects the lag phase?

A

what are the condictions and where the innoculum came from e.g the freezer

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15
Q

What is the formula for exponential growth?

A

N final = (N initial) 2n
N= the number of generations

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16
Q

What is cryptic growth?

A

Growing on dying cells- cells feeding on dying cells 2 expontentail growth periods

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17
Q

What is viable count?

A

It is a direct measurement and the measurement of living and reproducing population. There are 2 main ways to perform plate counts: spread-plate method or Pour-plate method
To obtain the appropriate colony number, the sample to be counted may need to be diluted (serial dilutions)

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18
Q

What is filtration?

A

The process in which solid particles in a liquid or gaseous fluid are removed by the use of a filter medium that permits the fluid to pass through but retains the solid particles

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19
Q

What factors affect bacterial growth?

A
  1. availabilIty of nutrients and H2O
  2. temperature
  3. moisture and drying
  4. radiation
    osmotic effects
  5. mechanical and sonic stress
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20
Q

What is the steady state?

A

after 5 volume changes inside a bioreacter

the volume is constant and the flow rate is 1 litre per hour

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21
Q

What is the diluation rate?

A

Dilution rate= flow rate / volume

22
Q

What is wash out?

A

wash out is when the dilution rate is faster than the microorganism growth rate

23
Q

What is total count and viable count?

A

total count- what u see and visulise

viable count- out of those how many are viable (not dead)

24
Q

Pros and cons of counting chambers?

A

advantage- easy to use, minimal set up
disadvantage- hard to tell if cells are viable or non-viable (don’t know if alive or dead)

25
Q

What is serial dilution?

A

have to diluate samples precisely in a mathmateically way. perfect plate

26
Q

What is the perfect plate with colonies

A

contains 30-300 colonies

27
Q

Pros and Cons of spreadable agar

A

agar cheap, used only for counting organisms that resulted in the formation of a colony CFUs colony forming units, but
need over night incubation

28
Q

What are indirect methods? and what are some examples?

A

indictor of microbial presense not looking at counting cells- looking at after effects

  1. metabolic activity
  2. dry weight
  3. turbidity
    4.Spectrophotometer
29
Q

What are metabolite examples?

A

CO2, H2O and any activity envolving metabolism and respiration

30
Q

When is a growth curve obtained

A

If bacteria counts are made at intervals after inoculation and plotted in relation to time it is obtained

31
Q

what phase are cells in the healthiest state

A

exponential

32
Q

what do diauxic growth curves have

A

2 logs

33
Q

what are examples of direct measurements for measuring growth

A

total cell count, counting chambers, viable count, filtration and most probable number

34
Q

What is total cell count?

A

direct microscopic examination using special slides, automated counters (flow cytometry)

35
Q

what is the most probable number

A

a statistical estimating technique

36
Q

What is spectrophotometer

A

measures the amount of light that passes through a sample. Absorbance is related to the number of bacteria

37
Q

what are looked at for measurements of growth

A

measurements of cell numbers, cell mass and cell constituants

38
Q

what are used for measurments of cell numbers?

A

Pore plate, spread plate, membrane filter, plating techniques and direct counting using Petroff Hausseer counting chambers

39
Q

what is used for measurements of cell mass?

A

dry weight, scattering of light in spectrophotometer

40
Q

what measured in cell constituents?

A

nucelic acids, chlorophyll, ATP and total protein or nitrogen

41
Q

what are pH of most bacteria

A

neutrophiles- pH 6.5-7.5
yeast and moulds have a pH of 4-6
some are acidophiles has a pH of less than 4
extremes sulfur oxiddisers can grow to pH 1-2
alkalophiles pH over 9- live in alkaline coils and water up to 11.5

42
Q

what are extremophiles

A

evolved to grow opitmally under very hot or cold temperatures

43
Q

what are thermophiles

A

loves heat and high temperatures

44
Q

what are hyperthermophiles

A

produce enzymes widely used in industrial microbiolgy eg taq polymerase and are very high temperatures

45
Q

what are psychrophiles

A

low temperature

46
Q

what are psychrotolerants

A

can grow at 0 degrees but have a optima of 20-40 degrees and are more widely distributed in nature than phychrophiles

47
Q

what are mesophiles

A

midrange temperature- found in warm-blooded animals, terrestrial and aquatic environments and temperature and tropial latitudes

48
Q

what are barophiles

A

organisms that live under extreme pressure for their membranes and enzymes depend on this pressure to maintain their 3 dimensional and functional shape

49
Q

what are aerobes

A

require oxygen to live

50
Q

what are anerobes

A

do not require oxygen and may be killed by exposure

51
Q

what are facultative organisms

A

can live with or without oxygen

52
Q

what are areotolerant anareobes

A

can tolerate oxygen and grow in its presense even though they cannot use it

53
Q

what are microareophiles

A

can use oxygen only when it is at levels reduced from the air

Microbiology (29 decks)

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