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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
Peroxide anion
O2 2-
26
hydroxyl radical
(OH*)
27
Organic Growth Factors
* Organic compounds obtained from the environment * Vitamins, amino acids, purines, and pyrimidine
28
Biofilms (2 of 3)
* 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
Biofilms (3 of 3)
* 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
culture medium
nutrients prepared for microbial growth
31
sterile
no living microbes
32
inoculum
introduction of microbes into a medium
33
Culture
microbes growing in or on a culture medium
34
Agar
– 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
Chemically defined media
exact chemical composition is known - Fastidious organisms are those that require many growth factors provided in chemically defined media
36
Complex media
extracts and digest of yeasts, meat, or plants; chemical composition varies batch to batch -Nutrient broth -Nutrient agar
37
Reducing media
-Used for the cultivation of anaerobic bacteria ̶ -Contain chemicals (sodium thioglycolate) that combine O2 to deplete it ̶ -Heated to drive off O2
38
Capnophiles
-microbes that require high CO2 conditions -CO2 packet -candle jar
39
Biosafety levels
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
Selective media
- suppress unwanted microbes and encourage desired microbes - contain inhibitors to suppress growth
41
differential media
allow distinguishing of colonies of different microbes on the same plate
42
Enrichment culture
* Encourages the growth of a desired microbe by increasing very small numbers of a desired organism to detectable levels * Usually a liquid
43
Obtaining pure cultures
* 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
Deep-freezing
* -50C to -95C
45
lyophilization (freeze-drying)
frozen (-54C to -72C) and dehydrated in a vacuum
46
Bacterial Division
* Increase in number of cells, not cell size * Binary fission * Budding * Conidiospores (actinomycetes) * Fragmentation of filaments
47
Generation time
* 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
49
50
51
Phases of growth
* Lag phase * Log phase * Stationary phase – Bacteria approach the carrying capacity * Death phase
51
direct measurements- count microbial cells
-plate count -filtration most probable number (MPN) method -direct microscopic count
51
Plate counts
* 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
Filtration
* Solution passed through a filter that collects bacteria * Filter is transferred to a Petri dish and grows as colonies on the surface
53
The Most Probable Number (MPN) Method
* Multiple tube test * Count positive tubes * Compare with a statistical table
54
Direct Microscopic Count
* 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
Turbidity
measurement of cloudiness with a spectrophotometer
56
metabolic activity
amount of metabolic products is proportional to the number of bacteria
57
dry weight
bacteria are filtered, dried, and weighed; used for filamentous organisms

Micro (8 decks)

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