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39 Cards in this Set
- Front
- Back
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Obligate aerobes (stricly aerobic) |
must have oxygen to grow (go dormant without oxygen) - growth occurs only where high concentrations of oxygen have diffused into the medium |
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Microaerophiles |
grow best at low oxygen levels (less than atmospheric) - growth only occurs where a low concentration of oxygen has diffused into medium |
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Facultative anaerobes |
use oxygen if present, but can also grow anaerobically (capable of growing at any oxygen level but greater growth with oxygen present) - growth is best where most oxygen is present, but occurs throughout the tube |
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Aerotolerant anaerobes |
never use oxygen, but not inhibited by it - growth occurs evenly; oxygen has no effect |
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obligate anaerobes |
grow only in absence of oxygen (inhibited by oxygen) - growth occurs only where there is no oxygen |
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Minimum Growth Temperature |
- lowest temp at which growth will occur (very slow growth) - below the minimum, most microorganisms go dormant, but do not die |
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Optimum Growth Temperature |
temp at which most rapid growth occurs |
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Maximum Growth Temperature |
- highest temp at which growth occurs - above this temp, enzymes are denatured and death might occur |
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Growth at Diff Temperatures |
Growth parallels rate of enzyme activity |
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Psychrophiles (Cryophiles) |
Cold-loving organisms - have an optimum growth temp below 25 degree C |
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Mesophiles (meso=middle) |
optimum of 25-40 degree C |
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Thermophiles |
heat-loving organisms - have optimum of >40 degree C |
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Hyperthermophiles |
growth range = 70-105 degree C Optimum >90 degree C |
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Chemical Requirements for Microbial Growth |
- carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen, and organic growth factors |
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Binary Fission |
- less complex than mitosis - only one chromosome |
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Microbial Growth |
- refers to number of cells, not the size of cells - Microbes that are "growing" are increasing in number accumulating into clumps of hundreds, colonies of populations of billions. |
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Plasmolysis |
- cytoplasm shrinkage due to a loss of water of a cell from being in a hypertonic solution |
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Halophiles (obligate vs. facultative) |
- organisms that require high salt concentrations for growth Obligate Halophiles: organisms that require a high salt cocentration for growth. Inoculating loops used to transfer these must first be dipped in a sline solution. |
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Acidophiles |
- organisms that thrive under highly acidic conditions (usually at pH 2.0 or below).
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Psychrotrophs |
- grow at 0 degree C but optimum at 20-30 degree celsius - these grow fairly well at low refrigerator temperatures and cause food spoilage (they provide an estimation of food's shelf life) |
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Classify microbes into groups based on preferred temperature ranges |
Psychrotrophs (cold-loving) Mesophiles (moderate-temperature loving) Thermophiles (heat-loving) Hyperthermophiles (extreme heat-loving) |
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Explain why the pH of culture media is controlled |
- because most bacteria grow best in a narrow pH range near neutrality and bacteria often produce acids that interfere with their own growth - peptones/amino acids/phosphate salts are used as Buffers to neutralize acids |
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Explain the importance of osmotic pressure to microbial growth |
Most microorganisms must be grown in a medium that is nearly all water. They obtain almost all their nutrients in solution from the surrounding water. |
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Explain how microbes are classified on the basis of oxygen requirements |
Obligate Aerobes Facultative Anaerobes Obligate Anaerobes Aerotolerants Anaerobes Microaerophiles (Draw Table 6.1!!!!) |
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Biofilms |
- thin, slimy layer encasing community bacteria that adheres to a surface - coordinated, functional community capable of quorum sensing and transfer of genetic information |
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Culture medium |
a nutrient material prepared for the growth of microorganisms in a laboratory |
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Colony |
a visible mass of microorganisms all originating from a single mother cell, therefore a colony constitutes a clone of bacteria all genetically alike.
Microbial colonies often have a distinctive appearance that distinguishes one microbe from another |
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Binary Fission |
1. Cell elongates and DNA is replicated. 2. Cell wall and plasma membrane begin to constrict. 3. Cross-wall forms completely separating the two DNA copies. 4. Cell separate. |
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Bacterial Growth Curve |
1. Lag Phase: Intense activity preparing for population growth, but no increase in population. During the lag phase, there is little or no change in the number of cells, but metabolic activity is high. 2. Log Phase: Logarithmic, or exponential increase in population. During the log phase, the bacteria multiply at the fastest rate possible under the conditions provided. 3. Stationary Phase: Period of equilibrium; microbial deaths balance production of new cells. During the stationary phase, there is an equilibrium between cell division and death. 4. Death Phase: Population is decreasing at a logarithmic rate. also called Logarithmic Decline Phase During the death phase, the number of deaths exceeds the number of new cells formed. 5. Survival Phase :D |
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Culture media: Chemically Defined |
Purpose: Growth of chemoautotrophs and photoautotrophs; microbiological assays |
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Complex Culture Media |
Purpose: Growth of most chemoheterotrophic organisms |
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Reducing Culture Media |
Purpose: Growth of obligate anaerobes |
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Selective Culture Media |
Suppression of unwanted microbes; encouraging desired microbes |
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Differential Culture Media |
Differentiation of colonies of desired microbes from others |
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Enrichment |
Similar to selective media but designed to increase numbers of desired microbes to detectable levels |
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Lyophilization (freeze-drying) |
1. Suspension of microbes is quickly frozen at temps -54C to -72C 2. Water is removed by a high vacuum (sublimation) 3. While under vacuum, container is sealed by melting the glass with a high-temp torch 4. Remaining powderlike residue contains surviving microbes that can be stored for years 5. Organisms can be revived at any time for hydration with suitable liquid nutrient medium |
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Biosafety Levels |
Biosafety Level 1 (BSL-1): basic microbiology teaching laboratory Biosafety Level 2 (BSL-2): handle organisms that present a moderate risk of infection - open laboratory benchtops with appropriate gloves, lab coats, face/eye protection Biosafety Level 3 (BSL-3): intended for highly infectious airborne pathogens ie. tuberculosis - biological safety cabinets, laboratory should be negatively pressurized and equipped with air filters Biosafety Level 4 (BSL-4): "hot zone" extraordinary systems of containment, only a handful exist in US. Personnel wear "space suits" for PPE and the air is filtered at least twice. |
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Justification for Using Living Host Cells |
many bacteria cannot be grown in artificial laboratory media because of their specific growth requirements ie. Mycobacterium leprae is grown in armadillos due to their low body temperature that allows for growth in this bacteria |
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Justification for Anaerobic Techniques |
1. Reducing media 2. Anaerobic chamber - used for growing obligately anaerobic bacteria that may be killed or their growth halted in the presence of oxygen |
