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BIO 425: Microbiology > Lecture 5: Microbial Growth > Flashcards

Lecture 5: Microbial Growth Flashcards

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Biology 101 flashcards
1
Q

What is Cell growth?

A

Increase in cell number

-Growth = reproduction

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2
Q

What is binary fission?

A

Division of 1 cell into 2 cells

-Divides through elongation and septum formation

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3
Q

What is generation time?

A

Time required for binary fission

-30min to 6hrs typically

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4
Q

What factors affect generation time?

A

Environmental Factors
-Nutrient availability and temperature

Genetic Factors
-Specific to different microbial species

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5
Q

What is the Divisome?

A

Collection of FTS Proteins embedded in cytoplasmic membrane that direct cell division in prokaryotes

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6
Q

What does FTS stand for?

A

Filamenting Temperature Sensative

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7
Q

What proteins make up the Divisome?

A

FtsZ
ZipA
FtsA
Ftsl

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8
Q

What does the FtsZ protein do?

A

Forms ring around center of the dividing cell

-Related to tubulin

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9
Q

What does the ZipA protein do?

A

Connects FtsZ ring to Cytoplasmic Membrane

-The “Anchor”

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10
Q

What does the FtsA protein do?

A

Attracts the other Fts proteins to form the divisome

-The “Recruiter”

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11
Q

What does the Ftsl Protein do?

A

Peptidoglycan synthesis
-Synthesizes peptidoglycan for the newly formed cell walls in order to complete separation

Good for new antibiotics or Drug design
-Target this (Or any) protein = prevent bacterial growth

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12
Q

What is the MreB protein?

A

Part of cell morphology
-Forms cellular cytoskeleton

Absent in Coccoid bacteria
Present in Rod-shaped bacteria

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13
Q

What kind of growth does a microbial population experience? What are the applications of this?

A

Exponential growth

  • Cells double EACH generation (1->2->4->8 etc)
  • So the rate increases each generation

Applicable to standards for bacterial counts in food

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14
Q

What are the different phases of the growth cycle for a bacterial population in a CLOSED SYSTEM (No nutrients in and No waste products out)?

A

Lag Phase
Exponential Phase
Stationary Phase
Death Phase

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15
Q

What is the lag phase of microbial growth?

A

Low (but positive) growth rate

-Recovering from transfer to nutrient agar (lab conditions but also wild)

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16
Q

What is the Exponential Phase of Microbial Growth?

A

Big jump in growth rate

-Maximal rate, all cells dividing

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17
Q

What is the Stationary Phase of Microbial growth?

A

Net Growth rate = 0
-Nutrients begin depleting and waste products accumulating

Also known as “Cryptic Growth”
-# of cells dividing = # of cells dying

18
Q

What is the death phase of microbial growth?

A

Growth Rate Negative

19
Q

What is a Continuous Culture? What is an Example?

A

Continuous Culture is an open system

Example is Chemostat

  • Nutrient Rich broth in
  • Waste products out
20
Q

What are some controls and applications of a continuous culture?

A

Controls

  • Dilution rate (How fast in/out)
  • Nutrient concentration

Applications
-Ecology and physiology

21
Q

What are the methods for measuring microbial growth?

A

Microscopic Counts
-Cell counts (Both living/dead)

Viable Counts

  • Plate counts (living)
  • # of colonies that form = # of cells in sample
22
Q

What are the advantages/disadvantages of Microscopic Counts for measuring microbial growth?

A

Advantages
-Simple method

Disadvantages

  • Counts living/dead
  • Difficult with low cell number and/or motile cells
23
Q

What are the advantages/disadvantages of Viable Counts for measuring microbial growth?

A

Advantages

  • High sensitivity
  • Counts only viable cells

Disadvantages
-Possible errors (Cell clumps, plating inconsistencies)

24
Q

What is the Turbidimetric Method for measuring Microbial growth?

A

Using light shined through vials with sample and measuring with spectrophotometer
-Cell mass = Cell Number

25
Q

What are the advantages/disadvantages for using the Turbidimetric method for measuring microbial growth?

A

Advantages

  • Simple method
  • Non-destructive (don’t have to throw away sample)

Disadvantages
-Possible errors (cell clumps + Biofilms)

26
Q

What are the cardinal temperatures?

A

Minimum: below this temp = no growth
Optimal: at this temp = fastest growth
Maximum: above this temp = cell death

Differ for each species of microorganism

  • Limited Temp (25-40 degrees Celsius)
  • Proteins within each microbe function at specific temp
27
Q

What are the different temperature classifications for microbes that live in different environments?

A 
Psychrophile = (< 15 degrees C)
Mesophile = Moderate
Thermophile = (> 45 degrees C)
Hyperthermophile = (>80 degrees C)

Anything that isn’t a Mesophile = Extremophile

28
Q

What kind of Microbe lives in the cold? Where are they found?

A

Psychrophiles

  • Slow growing in pockets of water
  • Deep Oceans, Glaciers, Polar Regions
29
Q

What kinds of molecular adaptations have Psychrophioles developed for their environment?

A

Cytoplasmic membrane contains much more Unsaturated/Short Chain Fatty Acids
-This causes the membrane to be more loosely packed and fluid at low temperatures

Cyroprotectants

  • Cold Shock Proteins
  • Antifreeze for cell
  • Ice that forms inside cell will cause PHYSICAL damage
30
Q

What kinds of Microbes live in hot/very hot temps? Where are they found?

A

Thermophiles and Hyperthermophiles
-Hot springs, Surface Soils, Water

Throwback to life on early earth

31
Q

What kinds of molecular adaptations have Thermophiles/Hyperthermophiles developed for their environment?

A

Cytoplasmic Membrane has more Saturated/Long Chain Fatty Acids
-Provides more stability at high temps

Heat Protectants
-Heat Shock Proteins (chaperones - as protein begins to denature, holds it together)

More Ionic Bonds

32
Q

What biotechnological applications have extremophiles played a role in?

A

Polymerase Chain Reaction (copying DNA)

  • Cyclical heating (denature) of DNA to 94 degrees C
  • Add in DNA Polymerase to add on new strand each cycle
Taq Polymerase (From Hot spring bacteria)
-using this heat resistant DNA Polymerase from extremophile prevents you from having to add more DNA polymerase each cycle
33
Q

Is there an upper temperature limit for life?

A

So far ~125 degrees celsius

  • Above 100 degrees celsius only archaea live
  • As time passes we’ll probably discover more that live at higher temps
34
Q

What other factors affect microbial growth besides temperature?

A

pH
Water
Oxygen

35
Q

What are the two types of microbes that live in different pH environments?

A

Acidophiles
-Optimal growth < pH 5.5

Alkaliphiles
-Optimal growth < pH 8

36
Q

How does Water availability affect microbial growth?

A

Water Amount
-Moist vs dry habitat

Dissolved Solutes in Water

  • Low vs High concentration of solutes in water
  • High solute concentration = dessication/water loss from microbial cell
37
Q

What are xerophiles, Osmophiles, Halophiles?

A

Xerophiles: Can grow in areas with low availability of water

Osmophiles: Can grow in areas with high Osmotic Pressures (High sugar concentration)

Halophiles: Can grow in areas with salt concentration

38
Q

What is an Aerobic Microorganism and what are the types?

A

Growth in the presence of oxygen

Obligate Aerobe: Oxygen required, only aerobic respiration

Facultive Aerobe: Oxygen not required but grows better with it. Aerobic/Anaerobic/Fermentation

Microaerophilic Aerobe: Oxygen required but at lower levels than atmospheric. Aerobic Respiration only

39
Q

What is an Anaerobic Microorganism and what are the types?

A

Aerotolerant Anaerobe: Oxygen not required but grows better without it. Fermentation only.

Obligate Anaerobe: Oxygen lethal/harmful. Fermentation or anaerobic respiration

40
Q

How do you reduce microbial growth?

A

Low Temp = Refrigeration
Low pH = Pickling
Low Water = Drying
Low Oxygen = Vacuum Sealing

BIO 425: Microbiology (22 decks)

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