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MBIO1010 > Chapter 5: Microbial Growth > Flashcards

Chapter 5: Microbial Growth Flashcards

(70 cards)

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1
Q

Growth

A

Measured as an increase in the number of cells

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2
Q

Binary fission

A

Cell division following enlargement of a cell to twice its minimum size

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3
Q

Generation time

A

Time required for microbial cells to double in number

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4
Q

Each daughter cell receives during cell division

A

A chromosome and sufficient copies of all other cell constituents to exist as an independent cell

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5
Q

What occurs simultaneously in bacteria and archaea?

A

Growth in cell size, chromosome replication, and septum formation

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6
Q

Is there mitosis in bacteria and archaea?

A

No

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7
Q

Generation time is dependent on

A

Growth medium and incubation conditions: carbon source, pH, temperature, etc.

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8
Q

Exponential growth

A

Growth of a microbial population in which cell number double at a constant and specific time interval

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9
Q

What kind of curve does exponential growth create?

A

One that has a slope that increases continuously

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10
Q

Growth rate (k)

A

Rate of increase in population number or biomass.

Expressed in bacteria and archaea as number of doublings per hour

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11
Q

Generation time

A

Time it takes for each to cell to become 2 cells

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12
Q

Specific growth rate

A

Fastest growth rate in the best medium and optimal temperatures

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13
Q

Batch culture

A

Closed-system microbial culture of fixed volume

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14
Q

Lag phase

A

Interval between inoculation of a culture and beginning of growth

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15
Q

Exponential phase

A

Cells in this phase are typically in the healthiest state

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16
Q

Stationary phase

A

Cells metabolically active, but growth rate of population is zero

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17
Q

Why is growth rate in stationary phase zero?

A

Either an essential nutrient is use up, or waste product of the organism accumulates in the medium

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18
Q

Death phase

A

If incubation continues after cells reach stationary phase, the cells will eventually die

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19
Q

Do all bacteria die in the death phase?

A

Some bacteria form spores/cysts or dormant stage that allow a significant proportion of cells to survive for a long time

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20
Q

Continuous culture

A

Open-system microbial culture of fixed volume

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21
Q

Chemostat

A

Most common type of continuous culture device

Both growth rate and population density of culture can be controlled independently and simultaneously

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22
Q

Dilution rate

A

Rate at which fresh medium is pumped in and spent medium is pumped out

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23
Q

Concentration of limiting nutrient controls

A

Population size and the growth rate

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24
Q

How are microbial cells counted by direct microscopic observations?

A

Petroff-Hausser counting chamber

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25
Petroff-Hausser counting chamber
Each square corresponds to a calibrated volume
26
Limitations of microscopic counts
- Cannot distinguish between live and dead cells without special stains - Small cells can be overlooked - Precision is difficult to achieve - Phase-contrast microscope required if a stain is not used - Low density cell suspensions are hard to count - Motile cells need to be immobilized - Debris in sample can be mistaken for cells - Brownian motion, some forms clumps
27
Flow cytometer
Second method for counting cells in liquid samples | Uses laser beams, fluorescent dyes, and electronics
28
Viable cell counts (plate counts)
Measurement of only living cells capable of growing to form a population
29
Methods of plate counts
Spread-plate method | Pour-plate method
30
Viable count issues
- Preparation and incubation time - Unreliable on counts of natural samples - Culture media and growth conditions can't grow every microbe
31
The great plate anomaly
Direct microscope counts of natural sample reveal far more organisms than those recoverable on plates
32
How much microbial diversity is culturable?
1-10%
33
What supports the great plate anomaly?
Microscope methods count dead cells, whereas viable methods do not Different organisms may have vastly different requirements for growth
34
Turbidity measurements
Indirect, rapid, and useful methods of measuring microbial growth
35
How is turbidity measured?
With a spectrophotometer
36
What is turbidity measured in?
Optical density
37
Why is turbidity measured in optical density?
Bacteria behave like small particles and absorb and scatter light
38
The larger the number of particles...
The greater the absorbance and the lower the light transmission to the photocell
39
Does absorbance distinguish cells?
No it can't tell live cells from dead cell or if it's chemical particles
40
Does turbidity require a stain?
No they do not disturb the sample
41
How is direct cell related to turbidity?
A standard curve must first be established to another counting method
42
What other counting methods are there?
Viable cell count Weight of biomass produced Measuring other parts of the cell which are proportional the the whole mass of cells
43
Issues with optical density
- Has a finite linear range of measurement - Only works if the cells are evenly distributed throughout the medium - Cuvette must not have scratches - Culture may need to be diluted when the cells are at a very high density
44
Cardinal temperature
Minimum, optimum, and maximum temperatures at which an organism grows
45
Psychrophile
Low temperature
46
Mesophile
Midrange temperature
47
Thermophile
High temperature
48
Hyperthermophile
Very high temperature
49
Where are mesophiles found?
In warm-blooded animals, terrestrial and aquatic environments, temperate and tropical latitudes
50
Extremophiles
Organisms that grow under very hot or very cold conditions
51
Psychrophile temperature optima
Less than 20 degrees celsius
52
Psychophile environments
Permanently cold environments: deep oceans, Arctic and Antarctic environments
53
Psychotolerant
Organisms that can grow at 0 degrees celsius but have optima of 20-40 degrees celsius
54
Molecular adaptations that support psychrophily
Production of enzymes that function optimally in the cold | Modified cytoplasmic membranes - high unsaturated fatty acid content
55
What life forms exist at above 65 degrees celsius?
Prokaryotes - chemorganotrophic and chemolithotrophic
56
What is the upper limit temperature of phototrophy?
70 degrees celsius
57
Thermophile optimal temperature
45-80 degrees celsius
58
Hyperthermophile optimal temperature
Greater than 80 degrees celsius
59
Hyperthermophile environments
Boiling hot springs and seafloor hydrothermal vents
60
Methanopyrus kandleri
Archaeon that can grow at 122 degrees celsius
61
Molecular adaptations to thermophily
Specific modifications provide thermal stability to enzymes and proteins Modifications in cytoplasmic membranes to ensure stability
62
Bacteria have what to survive high temperatures
Lipids rich in saturated fatty acids
63
Archaea have what to survive high temperatures
Lipid monolayer rather than bilayer
64
What produces enzymes widely used in industrial microbiology?
Hyperthermophiles
65
Taq polymerase
Used to automate the repetitive steps in the polymerase chain reaction technique
66
Hydrolytic enzymes
Proteases, cellulases, lipases
67
True/false: enzymes of thermophiles are more stable and tend to have higher activity than mesophilic counterparts
True
68
What are the upper temperature limits for life?
Suggested at 140-150 degrees celsius
69
What are the closest descendants of ancient microbes?
Hyperthermophiles
70
What supports the theory that hyperthermophiles are the closest descendants?
- Are found on the deepest, shortest branches of phylogenetic tree - Oxidation of H2 is common to many hyperthermophiles and may have been the first energy-yielding metabolism

MBIO1010 (13 decks)

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