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Micro > Micro Exam-2 Ch. 6 > Flashcards

Micro Exam-2 Ch. 6 Flashcards

1
Q

Physical Requirements for Growth of Microbes

A
  • Temperature
  • pH
  • Osmotic pressure
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2
Q

Chemical Requirements for Growth of Microbes

A
  • Carbon
  • Nitrogen, sulfur, and phosphorous
  • Trace elements
  • Oxygen
  • Organic growth factors
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3
Q

Temperature Growth Requirements

A

• Minimum, optimum and maximum growth temperature

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4
Q

Mesophiles, Optimum Temp, Examples

A

10-50 degrees Celsius, best survives at 37 degrees Celcius, Many spoilage and disease causing organisms.

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5
Q

Thermophiles, Optimum Temp, Examples

A

40-70 degrees Celsius, found in Hot Springs & organic compost, Endospores of thermophilic bacteria are heat resistant

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6
Q

Hyperthermophiles

A

65-110 degrees Celsius, Members of archaea found in hot springs, volcanic activity, deep sea hydrothermal vents

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7
Q

Growth of Bacteria from 0 to -30 degrees Celsius

A

No significant growth below freezing.

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8
Q

Growth of Bacteria from 15 to 50 degrees Celsius

A

Rapid growth of bacteria; some may produce toxins.

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9
Q

Most bacteria grow at what pH?

A

6.5 and 7.5

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10
Q

Molds and Yeast grow at what pH?

A

between pH 5 to 6

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11
Q

Acidophiles grow at what pH?

A

grow in acidic environments below 4.6 pH

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12
Q

Classification

Acidophile

A

1-5.5 pH Mechanism to exclusion of protons to maintain their internal pH at a higher level

Chemoautotrophic-bacteria found in drainage water from coal mines oxidizes sulfur to sulfuric acid and can survive at pH 1

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13
Q

Classification

Neutrophile

A

5-9 pH Majority of microorganisms falls in this range

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14
Q

Classification

Alkalophiles

A

8.5-11.5 pH Bacillus and micrococcus (take up protons to maintain internal pH)

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15
Q

What are some examples of buffers added to media to maintain proper pH?

A

peptones, amino acids, phosphate salts

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16
Q

Intracellular pH should be maintained above certain critical pH for the viability of the cell
It is normally accomplished in 3 ways

A

I. Homeostatic response
II. Acid tolerance response (ATR)
III. Acid shock protein synthesis

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17
Q

Homeostatic response

A

Helps cell to maintain pH under mildly acidic conditions (pH > 6)

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18
Q

Acid tolerance response (ATR)

A

At pH as low as 4. ATR also induces resistance to other environmental factors such as temperature, osmotic stress, etc.

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19
Q

Acid shock protein synthesis

A

Acid shock proteins are set of trans- acting regulatory proteins triggered by pH 3-5 range.

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20
Q

External pH can regulate expression of genes governing

A
  • proton transport
  • amino acid degradation
  • adoption to acidic and basic conditions
  • virulence in case of pathogenic organisms
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21
Q

Osmotic Pressure

A
  • Water is critical for growth of microorganisms
  • 70-80% of cell composition is water
  • They obtain nutrients from surrounding water
  • Osmotic pressure should be maintained for cell survival
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22
Q

Osmotic Pressure

A
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23
Q

Hypertonic Condition

A

High external solute concentrations causes water to pass out of cells plasmolysis

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24
Q

Isotonic Condition

A

equilibrium in uptake and release

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25
Hypotonic Condition
Rigid cells take up water to become turgid
26
Extreme or obligate halophile require what kind of osmotic pressure
require high osmotic pressure (high salt)
27
Facultative halophiles require tolerate what level of osmotic pressure?
High level osmotic pressure
28
Plasmolysis | -Cell in isotonic solution.
Under these conditions, the solute concentration in the cell is equivalent to a solute concentration of 0.85% sodium chloride (NaCl).
29
Plasmolysis | Plasmolyzed cell in hypertonic solution
If the concentration of solutes such as NaCl is higher in the surrounding medium than in the cell (the environment is hypertonic), water tends to leave the cell. Growth of the cell is inhibited.
30
Carbon Importance
* Structural backbone of living cells * Carbon is needed for all organic molecules which makes living cells * Half of the dry weight of typical bacterial cell is Carbon
31
• Chemoheterotrophs
obtain most of their Carbon from organic molecules (carbohydrates, proteins, lipids, etc.)
32
• Chemoautotrophs
and photoautotrophs use CO2 as their source Carbon
33
Nitrogen Importance
• Needed to synthesize cellular materials • Component of proteins, DNA, RNA and ATP • Nitrogen makes up 14% of dry weight of a bacterial cell • Most bacteria decompose protein material for the nitrogen source • Some bacteria use ammonium (NH +) or nitrate (NO –) 4 3 ions from organic material • A few bacteria use N2 from environment in nitrogen fixation
34
• Sulfur Importance
* Used in synthesis of amino acids, thiamine, and biotin * Most bacteria decompose protein for the sulfur source * Some bacteria use SO 2– or H S
35
• Phosphorus Importance
* Used in synthesis of DNA, RNA, and ATP * Found in cell membranes * PO 3– is a source of phosphorus
36
• K, Mg, & Ca
as cofactors for enzymes | • Inorganic elements like iron, copper, molybdenum, and zinc required in small amounts
37
Effect of Oxygen on Bacteria growth
38
What are biofilms
• Microbial communities • Form slime or hydrogels that adhere to surfaces • Bacteria communicate cell-to-cell via quorum sensing • Share nutrients • Shelter bacteria from harmful environmental factors
39
Biofilms
40
Where are biofilms found
* 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
41
• Culture medium:
nutrients prepared for microbial growth
42
• Inoculum
introduction of microbes into a medium
43
• Culture
microbes growing in or on a culture medium
44
• Sterile
No living microbes
45
Culture media
* Wide variety * Available from commercial sources * Premixed components + Water +Sterilization * Solid (agar) or liquid (broth) medium
46
• Agar
* Solidifying agent * Complex polysaccharide derived from marine alga * 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
47
Chemically defined media
exact chemical composition is known (Fastidious organisms are those that require many growth factors)
48
Complex media
• made up of nutrients including extracts of yeasts, meat, or plants, or digests of protein • chemical composition slightly varies from batch to batch • The energy, C, N and S requirements are primarily provided by protein • Nutrient broth; Nutrient agar
49
Anaerobic Growth Media and Methods | Reducing Media
* Used for the cultivation of anaerobic bacteria * Contain chemicals (sodium thioglycolate) that combine O2 to deplete it * Heated to drive off O2
50
• Capnophiles
* Microbes that require high CO2 conditions * CO2 packet * Candle jar
51
• Biosafety levels | BSL-1
no special precautions; basic teaching labs
52
BSL-2
lab coat, gloves, eye protection
53
BSL-3
biosafety cabinets to prevent airborne transmission | COVID
54
BSL-4
sealed, negative pressure; "hot zone" | • Exhaust air is filtered twice through HEPA filters
55
Selective Media
Suppress unwanted microbes and encourage desired microbes | Contain inhibitors to suppress growth
56
Differential Media
Allow distinguishing of colonies of different microbes on the same plate Some media have both selective and differential characteristics
57
Enrichment Culture
* Encourages the growth of a desired microbe by increasing very small numbers of a desired organism to detectable levels * Usually, a liquid
58
Culture Media Table
59
• A pure culture contains only
one species or strain
60
• A colony is a
population of cells arising from a single cell or spore or from a group of attached cells
61
• A colony is often called a
colony-forming unit (CFU)
62
• The streak plate method is used to
isolate pure cultures
63
• Deep-freezing
–50 degrees to –95 degrees C
64
• Lyophilization (freeze-drying):
frozen (–54 degrees to –72 degrees C) and dehydrated in a vacuum
65
Bacterial Division
• Increase in number of cells, not cell size
66
Binary Fission
Cell elongates and Cell wall and plasma membrane begin to constrict. Cross-wall forms, completely separating the two DNA copies. Cells separate.
67
• Budding
A group of environmental bacteria reproduces by budding. In this process a small bud forms at one end of the mother cell or on filaments called prosthecae. As growth proceeds, the size of the mother remains constant but the bud increases size
68
Conidiospores (actinomycetes)
any member of a heterogeneous group of gram-positive, generally anaerobic bacteria
69
Generation Time
* Time required for a cell to divide | * 20 minutes to 24 hours
70
• Binary fission doubles
the number of cells each generation | • Total number of cells = 2number of generations
71
Calculation for Log10 of number cells
72
• 1. Lag phase
* Metabolically active but no increase in number * ATP levels restored if necessary * Adaptation to new environment * Induce enzymes needed * Increase in size and unbalanced growth * Length varies with species and conditions
73
2. Log Phase
* Arithmetic plot of growth vs time yields curved line * Semi-log plot yields straight line * Population doubles each generation * Generation time range from 10 min to > 30 hr * Growth is asynchronous * Synchrous growth could be possible * Balanced growth –All cellular constituents made at constant rates
74
3. Stationary phase
* Growth curve horizontal * Population growth ceases * New cells made at same rate as old cells die (growth rate= death rate) * Reasons: Nutrient limitation, accumulation of toxic wastes, increase in cell density * Cultures may enter stationary phase with nutrient starvation * Changes in: Gene expression, peptidoglycan cross-linking, change in protein profiles * More resistant to unfavorable conditions * Period of long-term survival * Commonly when antibiotics are made
75
4. Death phase
* Number of viable cells decreases exponentially (i.e. constant no. of cells die per hour) * Bacterial cell death is defined by the inability to grow * Endospore formation takes place here with sporulating species
76
 Direct measurements
``` –count microbial cells • Plate count • Filtration • Most probable number (MPN) method • Direct microscopic count ```
77
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)
78
Filtration
* Solution passed through a filter that collects bacteria | * Filter is transferred to a Petri dish and grows as colonies on the surface
79
The Most Probable Number (MPN) Method
* Multiple tube test * Count positive tubes * Compare with a statistical table
80
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 Number of bacteria/ml = Number of cells counted/Volume of area counted
81
• Turbidity :
measurement of cloudiness with a spectrophotometer
82
Metabolic activity:
amount of metabolic product is proportional to the number of bacteria
83
Dry weight:
bacteria are filtered, dried, and weighed; used for filamentous organisms

Micro (7 decks)

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