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MicroBiology > CH 7 microbial growth natural v lab > Flashcards

CH 7 microbial growth natural v lab Flashcards

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1
Q

CH 7 Nat vs Lab

Growth in the natural environment

A 
Nutrients are typically a limiting factor - much less available with more competition
Oligotrophic environments:
- low nutrient levels
Surviving stravation
- starvation proteins
- spontaneous dormancy
- endospores and cysts
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2
Q

CH 7 Nat vs Lab

Synthesis of starvation proteins

A
  • Increase peptidoglycan crosslinking
  • Bind and protect DNA
  • Prevent protein denaturation
    Starved cells become more resistant to environmental stresses and pathogens may become more virulent
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3
Q

CH 7 Nat vs Lab

Spontaneous dormancy in nutrient-rich conditions

A

Portion of the microbial population enters dormancy on purpose - never know when nutrients may run low
Resistant to other environmental stresses

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4
Q

CH 7 Nat vs Lab

Biofilms

A

Organized community with multiple species encased in a protective slime layer. Cells attach to one another and to substrate. Generally one species’ waste is the others’ nutrients, and vice-versa. Ubiquitous in nature
Ex. dental plague, medical implants, urinary track infections, sinusitis, filters for sewage treatment, bioremediation of oil spills

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5
Q

CH 7 Nat vs Lab

Formation of biofilms

A

Reversible attachment - putting down proteins, conditioning surface for next species
Irreversible attachment - secretion of slime layer; microbial growth
Detachment - detachment or sloughing of cells

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6
Q

CH 7 Nat vs Lab

Quorum sensing

A

Chemical signaling to determine the number and type of cells in the surrounding environment - many things that bacteria do, they don’t like to do alone. - actions are effective only when a large number of cells are present.
utilization of nutrients, toxin production, bioluminescence
plasmid transfer–virulence

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7
Q

CH 7 Nat vs Lab

Growth in the lab

A

Optimized conditions for growth (plenty of nutrients, no competition, temp, pH), so they grow better in the lab than in nature.
Unfortunately, we can only grow 2% of known bacteria in the lab.

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8
Q

CH 7 Nat vs Lab

Culture media

A

All nutrients necessary for microbial growth.

Can be classified based on the physical state, chemical composition, and/ or function.

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9
Q

CH 7 Nat vs Lab

Physical state of media

A

Liquid (broth)
Semisolid
- used to look at bacterial motility, oxygen requirements
Solid
- usu. agar, but can be gelatin to ID certain bacteria. Agar melts ~90C and solidifies ~45C

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10
Q

CH 7 Nat vs Lab

Chemical composition of media

A

Defined

  • all chemical compositions and ratios known Complex
  • contain some ingredients of unknown composition and ratios
  • Yeast extract, beef extract, peptone, tryptone
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11
Q

CH 7 Nat vs Lab

Functions of media

A

Supportive: general bacterial growth
Enriched: fortified with extra nutrients (fastidious bacteria)
Selective: allows growth of some microorganisms while inhibiting others
Differential: distinguish among different groups of microorganisms

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12
Q

CH 7 Nat vs Lab

Fastidious bacteria

A

Those that require specific needs for growth, either/ both environmental and nutrient factors.

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13
Q

CH 7 Nat vs Lab

Blood agar

A

Can tell if the bacteria in the media are hemolytic or not - enriched and differential

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14
Q

CH 7 Nat vs Lab

Chocolate agar

A

Blood agar where the erythrocytes have already been lysed - enriched, but not differential

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15
Q

CH 7 Nat vs Lab

PEA

A

Phenylethanol Agar
Differential
Allows G+ to grow, but not G- because it is toxic to G-

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16
Q

CH 7 Nat vs Lab

MacConkey Agar

A

Selective: G+ over G-
Differential: identifies bacteria that can ferment lactose (lactose positive)

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17
Q

CH 7 Nat vs Lab

Eosin Methylene Blue

A

Selective

Differential: lactose positive or negative

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18
Q

CH 7 Nat vs Lab

Mannitol Salt Agar

A

High salt concentration

Differential: mannitol fermentation

19
Q

CH 7 Nat vs Lab

Growing Anaerobic microorganisms

A

Anaerobic media

  • can’t expose to oxygen, even when transferring between media
  • reducing agents turn oxygen into water
  • thioglycolate GasPak jar
    When working with obligate anaerobes, transfer between medias in a special hood with an inert gas
20
Q

CH 7 Nat vs Lab

Isolation of Pure Culture

A 
Colony - population of bacteria arising from single cell
Three types:
- streak plate
- spread plate
- pour plate
21
Q

CH 7 Nat vs Lab

Enrichment cultures

A

Adjust conditions to ID microorganisms with a specific characteristic.
ex. metabolics, antibiotic resistant

22
Q

CH 7 Nat vs Lab

Colony morphology

A

Each species has its own unique morphology - dealing with form, elevation, and margin.

23
Q

CH 7 Nat vs Lab

Characteristics looked for in identifying bacteria on morphology

A

Size
Texture of surface
Overall texture (butyrous, brittle, viscous)
Optical characteristics (opaque, translucent, dull, iridescent)
Pigment (most don’t produce color unless stressed)

24
Q

CH 7 Nat vs Lab

Types Cultures

A

Batch System

  • closed system with fixed nutrients Continuous System
  • constantly adding new media/ nutrients and removing waste
  • used in industry to produce proteins and other molecular components
25
Q

CH 7 Nat vs Lab

Growth Curve for Batch cultures

A

Lag phase > exponential phase > stationary phase > death and senescence phase

26
Q

CH 7 Nat vs Lab

Lag phase of growth curve

A

Subculturing bacteria from one media to another - takes some time for them to start actively growing again.
No increase in cell number - synthesizing cellular components

27
Q

CH 7 Nat vs Lab

Exponential phase of growth curve

A

Max rate of growth
Doubling at regular intervals (generation time)
Balanced growth
biochemical assays done at this time b/c the populations are uniform (physiologically the same)

28
Q

CH 7 Nat vs Lab

Stationary phase of growth curve

A

Some live and some dead cells
Nutrient availability decreasing and wastes building up
Critical population level = too dense (10 9 cells/ mL)

29
Q

CH 7 Nat vs Lab

Senescence and death

A

Irreversibly lose the ability to reproduce - viable but unable to grow
Apoptosis - some cells commit suicide to release nutrients for the other cells to keep living (through quorum sensing)

30
Q

CH 7 Nat vs Lab

Math of Growth

A 
g = generation time (cell # to double)
N t  = N o  x 2 n 
N t  is the cell # at time t
N o  is the initial cell #
n is the # of generations at time t
31
Q

CH 7 Nat vs Lab

Why is the math important?

A

Microbes in exponential phase are more susceptible to antimicrobial agents.
Exponential phase is favored because of uniform growth - major targets of antibiotics are proteins, cell walls, and DNA replication that occur during the exponential phase.
During senescence is when we see the production of starvation proteins.

32
Q

CH 7 Nat vs Lab

Measuring growth

A 
Direct cell counts
Viable cell counts
Biomass measurements
Detecting specific products from cells
***** be able to ID which is best to use in a given situation *****
33
Q

CH 7 Nat vs Lab

Direct cell counts

A

Petroff-Hausser counting chamber
Advantages:

  • quick, inexpensive, info about size and morphology Disadvantages:
  • labor intensive (tedious), culture must be densely populated, can’t distinguish dead from live cells (total cell count, not viable count)
34
Q

CH 7 Nat vs Lab

Petroff-Hausser counting chamber

A

Slide holds a known sample volume
Grid pattern assists in counting
Average number of bacteria per square is used to calculate concentration of the origin sample

35
Q

CH 7 Nat vs Lab

Coulter Counters

A

Cells are counted electronically - pass through opening in single file
Advantages:

  • quick, not labor intensive Disadvantages:
  • debris interferes with counting, works better for larger cells, can’t differentiate between dead and live cells
36
Q

CH 7 Nat vs Lab

Fluorescence and direct cell counts

A

Reagents used to distinguish between living and dead cells.
Can be used with coulter counters as well for more accurate results.
Often has higher concentration estimates than viable cell counts.

37
Q

CH 7 Nat vs Lab

Viable cell count

A

Examines the number of colony forming units.
Filter plate methods to check water samples - place filter onto plate of agar and count number of colonies that grow.
Advantages:

  • living cells, if using types of media you can begin to differentiate between types of bacteria
    Uses serial dilution, pour plate method, and then spread plate method.
38
Q

CH 7 Nat vs Lab

Biomass measurement

A

Dry weight determination (filter out of liquid culture)

Time consuming and not very sensitive/ accurate

39
Q

CH 7 Nat vs Lab

Spectrophotometry

A

Turbidity of culture increases as cell number increase
Measure absorbance/ scattering of light passing through the culture - proportional to the number of cells in a culture.
Advantages: quick and easy
Disadvantages: doesn’t distinguish living and dead cells

40
Q

CH 7 Nat vs Lab

Detecting cell products

A

Measure amounts of cellular products (ex. proteins or nitrogen levels)
Concentration of product has to be constant from one cell to another
Many industrial uses

41
Q

CH 7 Nat vs Lab

Continuous Culture System

A

Constantly adding nutrients and taking out wastes so the stationary phase is never reached.
Two types: chemostats and turbidostats

42
Q

CH 7 Nat vs Lab

Chemostats

A
  • fresh media is fed into system at fixed rate media has a limiting nutrient that regulates growth rate
  • all cells are in same stage of growth
  • maintain stage of growth for long periods of time

shut down if contaminated or if toxin from bacteria froms on the walls of apparaturs

43
Q

CH 7 Nat vs Lab

Turbidostats

A
  • maintain constant cell density
  • measure absorbance of the culture
  • flow rate of media is determined by turbidity (cloudiness) of the culture
  • media contains nutrients in excess, can allow maximal growth rate of cells

useful for photosynthetic microbes, can flush out some cells as add new nutrients

MicroBiology (18 decks)

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