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Micro > Ch. 6 Microbial Growth > Flashcards

Ch. 6 Microbial Growth Flashcards

1
Q

Physical requirements for growth

A

temp.
pH
Osmotic pressure

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2
Q

Chemical requierments for growth

A

-carbon
-nitrogen, sulfur, and phosphorous
-trace elements
-oxygen
-organic growth factors

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3
Q

Temperature

A

-minimum growth temp.
-optimum growth temp.
-maximum growth temp.

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4
Q

Psychrophiles

A

cold loving

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5
Q

mesophiles

A

moderate temp loving

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6
Q

theremophiles

A

heat loving

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7
Q

Pshychrotrophs

A

-grow between 0C and 20 to 30C
-cause food spoilage

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8
Q

Thermophiles

A

-optimum growth temperature of 50 to 60C
-found in hot springs and organic compost

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9
Q

Hyperthermophiles

A

-optimum growth temp. > 80C

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10
Q

pH

A
  • Most bacteria grow between pH 6.5 and 7.5
  • Molds and yeasts grow between pH 5 and 6
  • Acidophiles grow in acidic environments
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11
Q

Acidophiles

A

an organism that can or must live in an acidic enviroment

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12
Q

Osmotic Pressure

A
  • Hypertonic environments (higher in solutes than
    inside the cell) cause plasmolysis due to high
    osmotic pressure
  • Extreme or obligate halophiles require high
    osmotic pressure (high salt)
  • Facultative halophiles tolerate high osmotic
    pressure
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13
Q

Carbon

A

– Structural backbone of organic molecules
– Chemoheterotrophs use organic molecules as
energy
– Autotrophs use CO2

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14
Q

Nitrogen

A

– Component of proteins, DNA, and ATP
– Most bacteria decompose protein material for the
nitrogen source
– Some bacteria use NH4+ or NO3- from organic
material
– A few bacteria use N2 in nitrogen fixation

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15
Q

Sulfur

A

– Used in amino acids, thiamine, and biotin
– Most bacteria decompose protein for the sulfur
source
– Some bacteria use SO42 or H2S

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16
Q

Phosphorus

A

– Used in DNA, RNA, and ATP
– Found in membranes
– PO43 is a source of phosphorus

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17
Q

Trace elements

A
  • Inorganic elements required in small amounts
  • Usually as enzyme cofactors
  • Include iron, copper, molybdenum, and zinc
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18
Q

Obligate aerobes+

A

requires oxygen

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19
Q

Facultative anaerobes

A

grow via fermentation or anaerobic respiration when oxygen is not available

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20
Q

Anaerobes

A

unable to use oxygen and most are harmed by it

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21
Q

Aerotolerant anaerobes

A

tolerate but cannot use oxygen

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22
Q

microaerophiles

A

require oxygen conc. lower than air

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23
Q

Singelt oxygen

A

(1O2-) boosted to a higher-energy state and is reactive

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24
Q

Superoxide radicals

A

O2
O2-+O2- +2H —> H2O2 + O2

25
Q

Peroxide anion

A

O2 2-

26
Q

hydroxyl radical

A

(OH*)

27
Q

Organic Growth Factors

A
  • Organic compounds obtained from the environment
  • Vitamins, amino acids, purines, and pyrimidine
28
Q

Biofilms (2 of 3)

A
  • Microbial communities
  • Form slime or hydrogels that adhere to surfaces
    – Bacteria communicate cell-to-cell via quorum
    sensing
    – Bacteria secrete an inducer (signaling chemical)
    to attract other bacterial cells
  • Share nutrients
  • Shelter bacteria from harmful environmental factors
29
Q

Biofilms (3 of 3)

A
  • Found in digestive system and sewage treatment
    systems; can clog pipes
  • 1000x resistant to microbicides
  • Involved in 70% of infections
    – Catheters, heart valves, contact lenses, dental
    caries
30
Q

culture medium

A

nutrients prepared for microbial growth

31
Q

sterile

A

no living microbes

32
Q

inoculum

A

introduction of microbes into a medium

33
Q

Culture

A

microbes growing in or on a culture medium

34
Q

Agar

A

– Complex polysaccharide
– Used as a solidifying agent for culture media in
Petri plates, slants, and deeps
– Generally not metabolized by microbes
– Liquefies at 100C
– Solidifies at ~40C

35
Q

Chemically defined media

A

exact chemical composition is known
- Fastidious organisms are those that require many
growth factors provided in chemically defined
media

36
Q

Complex media

A

extracts and digest of yeasts, meat, or plants; chemical composition varies batch to batch
-Nutrient broth
-Nutrient agar

37
Q

Reducing media

A

-Used for the cultivation of anaerobic bacteria
̶
-Contain chemicals (sodium thioglycolate) that
combine O2 to deplete it
̶
-Heated to drive off O2

38
Q

Capnophiles

A

-microbes that require high CO2 conditions
-CO2 packet
-candle jar

39
Q

Biosafety levels

A

BSL-1: no special precautions; basic teaching
labs
̶
BSL-2: lab coat, gloves, eye protection
̶
BSL-3: biosafety cabinets to prevent airborne
transmission
̶
BSL-4: sealed, negative pressure; “hot zone”
▪ Exhaust air is filtered twice through HEPA
filters

40
Q

Selective media

A
  • suppress unwanted microbes and encourage desired microbes
  • contain inhibitors to suppress growth
41
Q

differential media

A

allow distinguishing of colonies of different microbes on the same plate

42
Q

Enrichment culture

A
  • Encourages the growth of a desired microbe by
    increasing very small numbers of a desired organism
    to detectable levels
  • Usually a liquid
43
Q

Obtaining pure cultures

A
  • A pure culture contains only one species or strain
  • A colony is a population of cells arising from a single
    cell or spore or from a group of attached cells
  • A colony is often called a colony-forming unit
    (CFU)
  • The streak plate method is used to isolate pure
    cultures
44
Q

Deep-freezing

A
  • -50C to -95C
45
Q

lyophilization (freeze-drying)

A

frozen (-54C to -72C) and dehydrated in a vacuum

46
Q

Bacterial Division

A
  • Increase in number of cells, not cell size
  • Binary fission
  • Budding
  • Conidiospores (actinomycetes)
  • Fragmentation of filaments
47
Q

Generation time

A
  • Time required for a cell to divide
    – 20 minutes to 24 hours
  • Binary fission doubles the number of cells each
    generation
  • Total number of cells = 2number of generations
  • Growth curves are represented logarithmically
48
Q
A
49
Q
A
50
Q
A
51
Q

Phases of growth

A
  • Lag phase
  • Log phase
  • Stationary phase
    – Bacteria approach the carrying capacity
  • Death phase
51
Q

direct measurements- count microbial cells

A

-plate count
-filtration
most probable number (MPN) method
-direct microscopic count

51
Q

Plate counts

A
  • Count colonies on plates that have 30 to 300
    colonies (CFUs)
  • To ensure the right number of colonies, the original inoculum must be diluted via serial dilution
  • Counts are performed on bacteria mixed into a dish
    with agar (pour plate method) or spread on the
    surface of a plate (spread plate method)
52
Q

Filtration

A
  • Solution passed through a filter that collects bacteria
  • Filter is transferred to a Petri dish and grows as
    colonies on the surface
53
Q

The Most Probable Number (MPN)
Method

A
  • Multiple tube test
  • Count positive tubes
  • Compare with a statistical table
54
Q

Direct Microscopic Count

A
  • Volume of a bacterial suspension placed on a slide
  • Average number of bacteria per viewing field is
    calculated
  • Uses a special Petroff-Hausser cell counter

of bacteria = # of cells counted/ vol. of area counted

55
Q

Turbidity

A

measurement of cloudiness with a
spectrophotometer

56
Q

metabolic activity

A

amount of metabolic products is proportional to the number of bacteria

57
Q

dry weight

A

bacteria are filtered, dried, and weighed; used for filamentous organisms

Micro (8 decks)

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