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MICROBIOLOGY > Module 3: Microbial Growth > Flashcards

Module 3: Microbial Growth Flashcards

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1
Q

3 Types of Microbial Growth

A
  1. Binary Fission
  2. Budding Cell Division
  3. Biofilm
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2
Q

Binary Fission

A
  • Organelles duplicated
  • DNA replication
  • Elongation; cell organelle migration to opposite poles; cleavage furrow
  • Septum Formation
  • Production of 2 Daughter Cells
  • INTERCALARY GROWTH
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3
Q

Budding Cell Division

A
  • Mother cell produces appendage which forms the daughter cell
  • Mother cell retains original size; appendaged is pinched off and deteriorated
  • POLAR GROWTH
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4
Q

Biofilm (and 3 Properties); matrix name

A
  • an assemblage of surface-associated microbial cells that are enclosed in an extracellular polymeric substance matrix
  • “microbial mat” one species on top of one another
  • EPS - exopolysaccharide matrix

3 Properties:
(i) Resistant to antibiotics or harmful chemicals - prevents entry
(ii) Hides them from protist grazer e.g. planktonic organisms (suspended in lipid environments)
(iii) Prevents being washed away by water

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5
Q

Generation Time (g)

A

Time taken for a cell to double

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6
Q

Solve for g (generation time)

A

g = t/n

g = 0.301/slope

g: generation time
t: time measurement
n: number of generations

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7
Q

Solve for N (final cell count)

A

N = N(0) x 2^n

N: final cell count
N(0): initial cell count
n: number of generations

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8
Q

Solve for n (number of generations)

A

n = 3.3[log(N) - log(N(0))]

n = [(log(N) - log(n(0))] / 0.301

n: number of generations
N: final cell count
N(0): initial cell count

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9
Q

4 Stages of Bacterial Growth Curve

A
  1. Lag Phase
    - adapting to a new, nutrient-rich environment
    - metabolically active but does not increase in cell number
  2. Exponential Phase
    - Cell Division occurs at a rapid rate
    - limiting factor: ATP production
  3. Stationary Phase
    - production of new cells at the same rate of cell death
  4. Death Phase
    - nutrients are depleted
    - overwhelming amount of toxic waste
    - cells undergo involution
    - endospore cells > vegetative cells
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10
Q

Duration of Lag Phase depends on

A
  1. Nutrients Available
  2. Species
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11
Q

Toxic Environment of Bacteria Growth Cycle

A
  1. Damaging pH
  2. Depletion of O2
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12
Q

Define Chemostat & 2 factors affecting cell density and growth rate

A
  • a system in which the chemical composition is kept at a controlled level, especially for the culture of microorganisms.
  1. Dilution Rate
  2. Concentration of Limiting Reactant
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13
Q

5 Methods of Bacterial Growth Measurement

A
  1. Direct Microscopic Count
    - counting via Petroff-Hauser counting chambers (both living and dead cells)
  2. Viable Cell Count
    - colony counting (spread plate, pour plate)
  3. Most Probable Number
    - estimate number of viable cells via gas production or turbidity
  4. Membrane Filtration count
    - physical separation of cells by size
  5. Turbidimetric Method
    - measuring via optical density and absorbance
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14
Q

Serial Dilution
Purpose, Range, Classifications and Process

A
  • PURPOSE: to lessen bacterial load by relegating it to single colonies
  • RANGE: 30-300 colonies
  • CLASSIFICATIONS: TFTC (too few to count), TNTC (too numerous to count)
  • PROCESS: constantly diluting the original inoculum by 1/10 to form 1:10, 1:100, 1:1000, 1:10000 plates
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15
Q

Dilution Factor DEFINE; EQUATION

A
  • DEFINE: Volume by which factor the sample was diluted
  • EQUATION: volume transferred of sample/total volume
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16
Q

Spread Plate
Pour Plate
Streak Plate

A
  • SPREAD: sample is pipetted onto AGAR plate; spread evenly before incubation
  • POUR: sample is pipetted onto sterile plate; sterile medium is added and mixed for solidification and incubation
  • STREAK: flame looped then applied like butter to agar plate
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17
Q

Colony Forming Units Equation

A

CFU/(mL or g): (# of counter colonies x dilution factor)/volume of plated sample

18
Q

The Great Plate Count Anomaly
and EXPLANATION

A
  • Direct cell counting w/ microscope of a cultivated medium reveals more than if sample was from the environment
  • Plate count shows lower number of cells

WHY?
- Entire bacterial population environment cannot be isolated in the laboratory
- Some may actually be nonviable (do not grow or divide), others are viable but nonculturable (VBNC)

19
Q

Solutions to Solve the Great Plate Count Anomaly

A
  1. Use of highly selective medium
  2. Varying incubation conditions
20
Q

Most Probable Number TYPE OF SAMPLE; 2 FACTORS; PROCESS

A
  • TYPE: Water and Air samples (It is used when samples contain too few bacteria to provide reliable viable cell numbers by classical plate count or if its unculturable in media)
  • 2 FACTORS: Gas Production and Turbidity (clear-ness property of solution)
  • PROCESS: undiluted mixture, 1:10, 1:100 of a bacterial sample are divided into 3 or 5 test tubes, +phenol red, results (count the # of positive test tubes) then use a table to determine the estimated number of bacteria cells
21
Q

Membrane Filtration PROCESS

A
  • physically separate
  • membrane filter
  • cotton plug in vacuum line ensures sterility
  • each colony growth captures one species of organism (in agar medium)
22
Q

Turbidimetric Method 2 FACTORS

A
  1. Optical Density
    - measures amount of attenutation of light (intensity lost)
    - based on light scattered
    - the slower the light travels, the higher the optical density
  2. Absorbance
    - measures amount of light absorbed
    - no basis on light scattered

OD measures HOW MANY cells
ABSORBANCE measures HOW LARGE cells

23
Q

What are the 4 Physical Properties that affect Microbial Growth?

A
  1. pH
  2. Temperature
  3. Osmosis pressure
  4. Oxygen
24
Q

Three classifications of pH and their pH ranges
What classification is E.coli?

A
  1. Neutrophiles
    - optimum pH 5.5 - 7.9
    - E.coli
  2. Acidophiles
    - <5.5
  3. Alkanophiles
    - >=8
25
Q

Name two kinds of commonly used buffers

A
  1. KH2PO4
  2. CaCO3
26
Q

What are Acidophiles?

A
  1. Acidithiobacillus feroxidase
  2. Picrophilus oshimae
27
Q

What are Akaliphilic?

A
  1. Agrobacterium sp.
    - Some can be Halophilic (salt-rich environments)
28
Q

4 Classifications of Microorganisms based on Temperature

A
  1. Psychrophile
    - optimal growth <15C
  2. Mesophilic
    - 10-50-ish growth range
  3. Thermophilic
    - optimal growth 45-80C
  4. Hyperthermophilic
    - Bacteria: up to 90C
    - Archaea: >100C
29
Q

Where are Thermophiles and Hyperthermophiles found?

A

Thermophiles: hot springs
Hyperthermophiles: geysers + hydrothermal vents

30
Q

Psychrophiles’ 4 Stability Properties (COLD ADAPTATIONS)

A
  1. Cytoplasmic membrane stability
    - high concentration of unsaturated, short chain fatty acids
    - maintains fluidity
  2. Lipids
    - contains polyunsaturated fatty acids
  3. Cold-Shock Proteins
    - maintains protein activity under low temperatures
    - binds to mRNA to facilitate translation process
  4. Cryoprotectant
    - antifreeze proteins
    - prevents ice crystal formation that can puncture cell membrane
    –> composed of GLYCEROL + DMSO (dimethylsulfoxide)
31
Q

Hyperthermophiles’ 2 Stability Properties (HOT)

A
  1. Proteins
    - protein folding
    - enzymes are more heat stable
  2. Membrane
    - lipids contain saturated fatty acids
    - Archaea: lipid monolayer - prevents membrane from peeling apart
32
Q

What are the Reactive Oxygen Species?

A
  1. Triplet & Singlet Oxygen
    - Singlet oxygen is highly reactive
    - Some organisms contain carotenoids which converts it into nontoxic forms
  2. Superoxide Anion & Hydroxyl Radical
    - strong oxidizing agents
    - destroyed by enzyme superoxide
  3. Hydrogen Peroxide
    - damaging to cellular components
    - destroyed by enzyme catalase & peroxidase
33
Q

Positive Water Balance

A

Cell cytoplasm has higher solute concentration so water flows into the cell

34
Q

4 Classifications of Halophiles and which is E.coli

A
  1. Nonhalophilic
    - E. coli
    - Low to no growth rate in presence of NaCl (salt)
  2. Halophilic
    - Increasing growth rate (up to a point) in increasing presence of NaCl
  3. Halotolerant
    - Growth rate isn’t influenced by salt concentration
  4. Extreme halophilic
    - Growth rate doesn’t increase until high concentration of salt is present
35
Q

Osmophilic

A

Thrives in high sugar environments

36
Q

Xenophilic

A

Thrives in dry environments

37
Q

What are Compatible Salts?

A

Solutes that can be used by the cell to protect its macromolecules (by increasing internal solute concentration to prevent the outflow of water)

38
Q

2 Methods of increasing internal solute concentration

A
  1. Pumping solutes into cell
  2. Synthesizing solutes
39
Q

3 Types of Aerobes

A

(i) Obligate
- required O2
- aerobic respiration
- skin/dust
(ii) Facultative
- not required, but better w/ O2
- aerobic respiration, anaerobic respiration, fermentation
- mammalian large intestine
- E. coli
(iii) Microaerophilic
- required but at lower levels of the atmosphere
- aerobic respiration
- lake water

40
Q

2 Types of Anaerobes

A

(i) Aerotolerant
- O2 not required; growth constant w/ O2
- fermentation
- upper respiratory tract
(ii) Obligate
- O2 is toxic
- fermentation or anaerobic respiration

41
Q

2 Types of Compatible Solutes and its corresponding

A
  1. KCl, Halobacterium sp.
  2. Proline, Staphylococcus sp.

MICROBIOLOGY (7 decks)

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