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Chapter 6
Microbial Growth
| Question | Answer |
|---|---|
| pyschrophiles - cold loving. temp? | -10 to -20 degrees |
| pyschrophiles are found where... | depths of ocean |
| pschotrophs are cold loving groups that cause food spoilage. this temperature is.... | 0-30 degrees celsius |
| moderate temperature groups are known as __ with a temp of... | mesophiles: 10 to 50 degrees celsius |
| thermophiles found in hot springs are... | 40-72C |
| hyperthermophiles temp: | 65-110 degrees celsius |
| where are hyperthermophiles found? | hot springs, volcanic activity, and archae members |
| what happens to microbial reproductive rates at low temperatures? | they decrease |
| what's the optimum temp for pathogenic bacteria? | 37 degrees |
| acidophiles | grow in acidic environments |
| molds and yeasts are a type of acidophiles that grow at what ph? | 5-6 |
| most bacteria grow at what ph? | 6.5-7.5 |
| acidic food are ___ likely to grow bacteria | less |
| extreme halophiles aka obligate halophiles requires... | high salt concentration for growth. requires high osmotic pressure |
| faculative halophiles ___ osmotic pressure | tolerates |
| what happens to osmotic pressure in HYPOtonic solutions? | very low |
| in HYPERtonic solutions, the osmotic pressure is... | very high |
| hypertonic environments cause ___ | plasmolysis (cell shrinkage) |
| obligate aerobe | requires o2 to grow |
| growth occurs when there is no o2 | obligate anaerobe |
| facultative anaerobes | anaerobic AND aerobic. |
| growth is best where most O2 is present but occurs throughout the entire tube. which oxygen requirement is this? | facultative anaerobes |
| microaerophiles grow in... | low o2 environment |
| aeroteolerant anaerobes cannot... | use o2 for growth but CAN grow in its presence |
| anaerobes require... | oxygen-free conditions to grow |
| which media is this --> exact chemical composition is known. | chemically defined |
| in ___media..extracts and digests of yeasts, meat or plants (nutrient agar and broth) | complex |
| reducing media... | chemicals that combine o2 --> heated to drive off o2 |
| why are reducing media used? | bc anaerobic bacteria might be killed by o2 |
| enrichment media are used for | isolation. encourages growth of desired microbe |
| how do we obtain a pure culture of bacteria? | 4 streak method |
| generation time | time it takes for a cell to divide and it's population to double. usually 1-3 hours |
| generation time depends on what 2 factors | organism and environment |
| which phase is the growth phase. reproduction most active here.. | log phase |
| the lag phase can last for 1hr-several days. what else occurs here? | little or no cells are dividing. this is our prep phase |
| in the stationary phase... | equilibrium. the death rate = growth rate (carrying capacity is reached) |
| number of deaths exceed the number of new cells formed. what phase is this known as? | death phase |
| 4 direct methods of measuring cell growth? | 1. plate count 2. MPN 3. filtration 4. direct microscope count |
| how many colonies are on a count plate? | 25-250 |
| disadvantage of plate counts? | takes 24hrs to see visible colonies |
| the plate count measures... | the number of viable cells |
| which method involves diluting a solution until there's no bacteria left? | most probable number method |
| absence of contamination is known as | asepsis |
| 3 indirect methods of measuring cell growth? | turbidity. metabolic activity. dry weight. |
| in dry weight... | fungus is removed and filtered, dried and weighed |
| in metabolic activity it assumes that the amount of certain metabolic product such as acid, co2, atp or dna = | the number of bacteria present |
Created by:
Mariahj25
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