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CBE 2290 > Module 7 > Flashcards

Module 7 Flashcards

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1
Q

What are 4 requirements for growth

A
  1. carbon source
  2. energy source
  3. inorganic nutrients
  4. favourable environmental conditions
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2
Q

What is the carbon source required for bacterial growth?

A

Carbon is required to synthesize new bacteria, represented by C5H7O2N (numbers are subscript)

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3
Q

How do cells derive energy?

A

Cells derive energy from redox reactions, which require an electron donor and a terminal electron acceptor

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4
Q

What are examples of inorganic nutrients needed for growth?

A
  • Nitrogen
  • Phosphorus
  • Metals
  • Vitamins
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5
Q

Name 2 favorable environmental conditions needed for growth:

A
  1. pH
  2. Temperature
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6
Q

How do reproductive strategies differ between eukaryotic microbes and bacteria/archaea?

A

Eukaryotes use mitosis and meiosis, while most bacteria and archaea reproduce by binary fission

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7
Q

What is mitosis in eukaryotes?

A

Mitosis is a form of asexual reproduction or cell division that results in 2 identical daughter cells

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8
Q

What is meiosis used for in eukaryotes?

A

Meiosis is used to produce gametes

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9
Q

how do most bacteria and archaea reproduce?

A

Most reproduce asexually through binary fission, producing 2 identical daughter cells

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10
Q

Please draw and label the Microbial Growth Curve

A

check notes for answer

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11
Q

growth can be measured in terms of:

A
  1. increase in cell numbers
  2. increase in cell size/mass
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12
Q

4 phases of microbiral growth?

A
  1. lag phase
  2. log phase
  3. stationary phase
  4. death phase
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13
Q

What occurs during the lag phase of microbial growth?

A

Cells synthesize new components and replenish materials while adapting to the new medium or conditions. The duration many be very short or absent in some cases

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14
Q

What is another name for the exponential phase of growth?

A

Also called the log phase

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15
Q

What happens in the log phase?

A

the rate of growth and division is constant and maximal. The growth rate depends on factors such as nutrient availability

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16
Q

What happens during the stationary phase?

A

The total number of viable cells remains constant. Metabolically active cells may stop reproducing, with the reproductive rate balanced by the death rate.

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17
Q

What can cause the stationary phase to occur?

A

factors such as nutrient limitation, limited oxygen, toxic waste accumulation, or reaching a critical population level

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18
Q

Describe the death phase of microbial growth:

A

The number of viable cells declines exponentially. Cells may be viable but non-culturable (VBNC), meaning they are alive but dormant.

This phase can also involve programmed cell death (apoptosis).

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19
Q

What is apoptosis?

A

Programmed cell death

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20
Q

What is the range of doubling times for microorganisms?

A

ranges from 10 minutes for some bacteria to several days for some eukaryotic microorganisms

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21
Q

During exponential growth, what are the assumptions made regarding growth?

A
  • the growth rate in independent of substrate concentration
  • there are no toxic by-products
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22
Q

What occurs during the lag phase of BATCH bacterial growth?

A

there is acclimation to the environment, and cells synthesize necessary components

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23
Q

What characterizes the log phase of BATCH bacterial growth?

A

characterized by multiplication at the max rate and rapid utilization of nutrients (S).

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24
Q

What happens during the stationary phase of BATCH bacterial growth?

A

Growth is offset by cell death, leading to a steady state where the number of viable cells remains constant

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25
What characterizes the death phase in BATCH bacterial growth?
characterized by the depletion of nutrients (S) and a decrease in cell number (X) due to cell death
26
What are the types of direct cell counts?
- counting chambers - electronic chambers
27
What is a counting chamber and its characteristics?
- easy, inexpensive and quick method - useful for counting both eukaryotes and prokaryotes - can't distinguish living from dead cells UNLESS combined with staining - designed with a known volume - calculates # cells/volume
28
How does flow cytometry work?
Flow cytometry analyzes physical and chemical characteristics of cells as they pass through a laser
29
What is a Coulter counter and how does it function?
- A Coulter counter forces a cell suspension through a small orifice - the movement of a cell disrupts an electric current flowing through the orifice - this disruption is counted electronically
30
What are the 2 common techniques used for viable counting methods?
1. Spread Plate Technique 2. Pour Plate Technique
31
How is a diluted sample prepared in viable counting methods?
A diluted sample of cells is spread over a solid agar surface or mixed with agar and poured into a petri plate
32
How are the numbers of organisms determined after incubation in viable counting methods?
The # of organisms is determined by counting the number of colonies and multiplying by the dilution factor
33
What unit is used to express the results of viable counting methods?
results are expressed as colony-forming units (CFU)
34
What are the advantages of viable counting methods?
They are simple, sensitive, and widely used for counting cells in food, water and soil
35
What limitations can affect the accuracy of viable counting methods?
Inaccurate results can occur if cells clump together or if cells are viable but non-culturable
36
How are cells filtered using membrane filters?
Cells are filtered through a membrane filter and trapped based on size exclusion
37
What is the purpose of staining cells with fluorescent dyes in membrane filtration?
It allows for the distinction between live and dead cells
38
What color do viable and damaged cells stain?
Viable cells = green Damaged cells = red
39
What is an alternative method to assess colony formation in membrane filtration?
The membrane can be cultured in a conducive medium to assess colony formation
40
What is the dry weight method in measuring cell mass?
The dry weight method is time-consuming and not very sensitive but is one way to measure cell mass
41
What are assays used for in cell mass measurment?
Assays can quantify particular cell constituents such as total protein, DNA, or specific enzymes, useful if the amount of the substance in each cell is constant
42
What are turbidometric or spectrophotometric techniques used for?
These techniques measure absorbance to determine cell mass quickly, easily, and sensitively
43
What is the definition of continuous culture?
Growth in a open system with constant environmental conditions, with a continual provision of nutrients and removal of waste products
44
What is the advantage of continuous culture?
It maintains cells in the log phase at a constant biomass concentration for extended periods
45
What does CSTR stand for?
Continuous Stirred Tank Reactor, a common type of continuous culture system
46
What is a Chemostat Bioreactor designed for?
Constructed so that the culture medium contains a limited quantity of an essential nutrient, and the rate of feed of sterile fresh medium equals the rate at which medium containing microorganisms is removed.
47
How is the growth rate determined in a Chemostat Bioreactor?
determined by the rate at which sterile medium is fed into the growth chamber
48
What does the dilution rate (D) in a Chemostat indicate?
D = Flow/Volume ; controlling the rate of nutrient exchange and being a constant for a given system
49
What happens to cell density in a Chemostat for a wide range of D?
The cell density remains stable and follows Monod growth kinetics
50
What are the effects of low and high dilution rates in a Chemostat?
Low D: nutrient supply is limited High D: washout can occur
51
What is a Turbidostat Bioreactor?
It is a continuous culture system system that uses a photo-detector to measure cell density in the reactor vessel
52
How does a Turbidostat regulate cell density?
It regulates the volume of medium added to maintain a desired turbidity, with all nutrients present in excess and variable dilution rates
53
What are similarities and differences between chemostat and turbidostat bioreactors?
Similar: they both maintain continuous growth by adding fresh medium and reducing excess culture Different: Turbidostat adds medium in response to changes in cell density whereas chemostat is at a fixed rate
54
Why are continuous culture methods important in microbiology?
They are useful for research in food, environmental, and industrial microbiology, maintaining a constant supply of cells in the exponential phase with a known growth rate
55
What do continuous culture methods allow researchers to study?
They allow for the study of cell growth at very low nutrient concentrations, close to those present in natural environments, and the interaction of cells under similar conditions
56
How are microorganisms affected by their environment?
Microorganisms are greatly influenced by chemical and physical environmental factors
57
What environmental factors impact microbial growth?
- solutes and water activity - pH - temperature - oxygen levels - pressure - radiation
58
What is the difference between barotolerant and barophilic microbes?
Barotolerant: affected by increased pressure but are more resistant than non-tolerant microbes Barophilic: grow more rapidly at high pressures
59
Why is it important to understand environmental factors in microbiology?
Crucial for designing systems for microbial growth and controlling microorganisms
60
How do microbes respond to changes in osmotic concentration?
Microbes are affected by changes in the osmotic concentration of their surroundings
61
What is a hypotonic environment?
A hypotonic environment has lower osmotic concentration outside the cell, causing water to enter the cell and potentially leading to cell swelling or lysis
62
What is a hypertonic environment?
Has a higher osmotic concentration outside the cell, leading to water exiting the cell, causing it to shrink (crenate)
63
What are osmotolerant microorganisms?
microorganisms that can grow over a wide range of osmotic concentrations
64
What is the difference between obligate and facultative microorganisms?
Obligate: require specific conditions to survive Facultative: can grow in a variety of conditions, including those without the preferred conditions
65
What is the difference between aerotolerant and facultative microorganisms?
Aerotolerant: can tolerate the presence of oxygen but do not use it for growth Facultative: can utilize oxygen when available but can also grow in its absence
66
How do most microbes grow in their environments?
Most microbes grow attached to surfaces (sessile) rather than being free-floating (planktonic)
67
What are biofilms?
complex, slime-enclosed communities of microbes that are ubiquitous in nature
68
Where are biofilms commonly found?
dental plaque, medical devices, pipes transporting fluids, coolant systems, and municipal water pipes
69
What is the initial step in biofilm formation?
Initially, microbes reversibly attach to a conditioned surface, with proteins first attaching to the surface
70
What stabilizes the attachment of microbes in biofilms?
The attachment becomes stabilized with the production of extracellular polymeric substances (EPS), which includes polysaccharides, pr-, glycopr-, glycolipids, and DNA
71
What protective functions does EPS serve in biofilms?
protects against harmful agents such as UV light, antibiotics, and antimicrobials
72
How do microorganisms communicate within a biofilm?
Interactions among attached organisms occur via quorum sensing
73
What is quorum sensing?
the process by which bacteria monitor their own population density
74
How is quorum sensing mediated?
mediated by small proteins (autoinducers) that increase in concentration as microbes replicate
75
What is a common autoinducer produced by many gram-negative organisms?
N-acyl-homoserine lactone (AHL) is a common autoinducer molecule
76
What happens to autoinducers once inside the cell?
Once at a threshold concentration, autoinducers can induce the expression of target genes that regulate various functions, such as DNA uptake for antibiotic resistance

CBE 2290 (12 decks)

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