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30 Cards in this Set
- Front
- Back
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Major phases of bacterial growth
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1. Lag phase
2. Log phase 3. Stationary phase 4. Decline phase |
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Cell division in yeast
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budding
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Cell division in bacteria
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binary fission
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Microbial growth
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increase in the number of cells (cell division)
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Generation time
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Time required for a population of organisms to double in number
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chemostat
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fresh medium continuously added to a growth chamber that makes it possible to grow organisms continuously in the log phase
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involution
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bacteria assume a variety of unusual shapes
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Neutrophiles
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Most of the bacteria that cause disease in humans are at this pH tolerance.
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Filtration
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Estimates the size of small bacterial populations
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Physical factors affecting bacterial growth
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pH, temperature, oxygen concentration, moisture, hydrostatic pressure, osmotic pressure, radiation.
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Most Probable Number
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used when samples contain too few organisms to give reliable measures by the plate count method
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Direct methods of measuring bacterial growth
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Standard plate count, serial dilutions, direct microscopy, MPN, filtration
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Indirect methods of measuring bacterial growth
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turbidity, measuring metabolic products, dye reduction test (oxygen), dry weight measurement
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Psychophiles
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cold loving organisms, grow best between 15 to 20 C or extreme 0 C
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Mesophiles
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Include most bacteria
Grow best 25 to 40 C. |
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Thermophiles
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Heat loving organisms
Grow best 50 to 60 C or extreme 115C |
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Cardinal Temperature
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Optimal temperature for a particular microbe (where cells divide most rapidly shortest generation time)
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hopanoids
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improve plasma membrane fluidity in bacteria. Increase rigidity and decrease fluidity (Like cholesterol in eukaryotes)
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Acidophiles
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acid-loving organism
grow best at pH 0.1 to 5.4 |
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Neutrophiles
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Most of the bacteria that cause human disease grow at this neutral condition.
grow at pH of 5.4 to 8.5 |
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alkaliphiles
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Base-loving (alkali) organisms
Exist at pH of 7.0 to 11.5 |
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Obligate aerobes
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must have free oxygen for aerobic respiration. grow near surface in a culture tube
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Obligate anaerobe
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Killed by free oxygen
Grow near the bottom in a culture tube |
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Facultative anaerobes
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most complex enzyme system
Can live with and without oxygen Carry aerobic metabolism when oxygen present. Shift to anaerobic metabolism when oxygen absent |
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Aerotolerant anaerobes
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Survive in the presence of oxygen
do not use it in their metabolism mostly fermentation |
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Microaerophiles
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grow best in the presence of small amount of free oxygen
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superoxide dismutase
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converts superoxide (O2-) to molecular oxygen (O2) + toxic hydrogen peroxide (H2O2)
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Catalase
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converts hydrogen peroxide (H2O2) into water + molecular oxygen (O2)
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Major Macronutrients for bacteria
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carbon
nitrogen sulfur phosphorous oxygen hydrogen |
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Minor Macronutrients
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trace elements
K, Zn, Mg, Mn, Ca, Fe, Co |
