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MB 351 - Exam 2 > Microbial Growth, Nutrition, and Culturing > Flashcards

Microbial Growth, Nutrition, and Culturing Flashcards

1
Q

Microbial Growth

A

Increase of the number of cells in a population, not the cell size

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2
Q

Steps in Binary Fission

A
  1. Cell elongates and DNA is replicated
  2. Cell wall and plasma membrane begin to constrict
  3. Cross-wall forms, completely separating DNA copies
  4. Cells separate
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3
Q

Lag Phase (4)

A
  • Length depends on “history”
  • Change in cell composition without division
  • Adaptation to new media conditions
  • Synthesis of damaged cell constituents
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4
Q

Log Phase

A
  • Cell count doubles in fixed time period

- Cells are most active (and good for experiments)

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5
Q

Log Number for Cell Count

A

Log Number = Log(Generation Number)
2^(Generation Number) = Number of Cells
[If starting with multiple cells, multiple cell number by the starting cell count]

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6
Q

Stationary Phase (3)

A
  • Growth limited by nutrient availability, toxic metabolites, or space
  • Dying cells = Dividing cells (Viable count is unchanging)
  • Important for secondary metabolite production and endospore formation
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7
Q

Death Phase (2)

A
  • Exponential loss of cell viability

- Essentially reverse log phase

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8
Q

Generation Time

A

“Doubling” time; time it takes a bacterium to do one binary fission

Number of Generations =
[ Log (#Cells-end) - Log (#Cells-beginning) ] / 0.301 (aka log(2))

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9
Q

Heterotrophs

A
  • Use organic molecules to supply carbon
  • Carbon source typically supplies H and O
  • Carbon source supplies energy
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10
Q

Autotrophs

A
  • Use inorganic CO2 as main carbon source

- Carbon source does not supply energy

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11
Q

Chemotrophs

A
  • Use chemicals as energy
  • Chemoheterotrophs: use organic chemicals
  • Chemolithotrophs: use inorganic chemicals
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12
Q

Phototrophs

A

-Use light as energy

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13
Q

Nitrogen Sources (4)

A
  1. Amino acids
  2. NH4+
  3. NO3-
  4. N2-Fixation
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14
Q

Sulfur Sources (2)

A
  1. S-amino acids (cysteine)

2. Sulfate (SO4^2-)

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15
Q

Phosphorus Sources

A

Mostly from Pi (PO4^2-)

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16
Q

Micronutrients (5)

A
  • Trace elements
  • Typically transition metals (e.g. Mn, Fe, Mo, Cu, B, Co)
  • Typically required in microgram quantities
  • Often present in laboratory water and glassware
  • Serve structural/catalytic roles in specific enzymes
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17
Q

Growth Factors

A
  • Typically small organic compounds (AAs, purine/pyrimidines, vitamins)
  • Required in varying concentrations
18
Q

O2 Growth Types

A 
Obligate Aerobe (Atm O2 ~20%)
Obligate Anaerobe
Facultative (Anaerobe/Aerobe)
Microaerophile
Aerotolerant anaerobe (Unaffected by O2)
19
Q

Toxic O2 Types

A
  1. Singlet oxygen (boosted to higher-energy state)
  2. Superoxide free radicals (O2- radical)
  3. Peroxide anion (O2^2-)
  4. Hydroxyl radical
20
Q

Psychrophile Range

A

-10-20

Optimal: 10-20

21
Q

Mesophile Range

A

10-45

Optimal: 20-40

22
Q

Thermophile Range

A

40-75

Optimal: >50

23
Q

Hyperthermophile Range

A

65-120

Optimal: >75

24
Q

pH Range

A
  • Most bacteria: 6.5-7.5
  • Acidophiles: Optimal below 6
  • Alkaliphiles: Optimal at 9 or higher
25
Q

Direct Microscopic Cell Counts

A
  • Doesn’t distinguish dead and live cells
  • Difficult to see small and unstained cells
  • Labor intensive
  • Motile bacteria hard to count
  • Can use Petroff-Hausser Cell Counter
26
Q

Viable Cell Counts

A
  • Use serial dilutions to obtain a colony count (e.g. dilute a mL to 1:10,000, count colonies, and multiply by dilution)
  • Need between 30-300 CFU/plate
  • Colony Forming Unit (CFU) is only related to viable number
27
Q

Turbidity Measurement

A
  • Spectrophotometer estimates large numbers of bacteria
  • Cannot detect densities less than 10^7 cells/mL
  • Cannot differentiate between live and dead cells
28
Q

Cultures that are closed with un-renewed nutrients and exponential growth limited to a few generations

A

Batch Cultures

29
Q

Bacterial cultures grown exponentially over a long time; population density remains the same; restores nutrients, removes wastes, and alleviates accumulation of cells

A

Continuous (Chemostat) Cultures

30
Q

Chemically Defined Media

A

Media in which the exact chemical composition is known

31
Q

Complex/Rich Media

A

Media in which the exact chemical composition is poorly defined; often made of natural source components (e.g. blood, yeast extracts, casein)

32
Q

Enrichment Culture

A

Uses specific substrates to enrich and isolate organisms with specific capabilities; contains important growth factor for a fastidious organism (e.g. nitrogen-fixers, hydrocarbon-utilizers)

33
Q

Selective Media

A

Inhibits the growth of unwanted organisms and supports the growth of desired ones (Brilliant Green dye [in agar] inhibits gram-positives and selects for gram-negatives)

34
Q

Differential Media

A

Allows for the separation of organisms based on an observable change in the appearance of the media (e.g. blood agar [turns clear in the presence of hemolytic activity])

35
Q

MacConkey Agar is…

A

a selective (inhibits gram-positive) and differential (lactose fermenters turn pink) media

36
Q

Biofilms (3)

A
  • Microbial communities that share nutrients, become sheltered from harmful factors
  • Form slimes or hydrogels
  • May be responsible for some chronic infections and diseases
37
Q

Bacteria can form biofilms by attraction to chemicals called…

A

Quorum sensing

38
Q

A cell in a hypertonic solution will…

A

Plasmolyze

39
Q

The macronutrients are…

A

C, H, N, O, P, S
and
K, Ca, Na, Mg, Fe

40
Q

Chemical Requirements for Growth

A
  • C, H, N, O, P, S
  • Micronutrients/Trace Elements
  • Growth Factors
  • Water
41
Q

Physical Requirements for Growth

A
  • Temperature
  • pH
  • Osmotic pressure

MB 351 - Exam 2 (4 decks)

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