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44 Cards in this Set
- Front
- Back
What is microbial growth?
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For microbial growth... 2 types of requirements |
______ requirements: Types of nutrients, Growth factors |
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For Microbial Growth (3 Choices)
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2. 3. |
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Physical Requirements for Microbial Growth - Temperature
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the internal temperature of a microorganisms is the same as that of the environment they are in not all microorganisms grow within the same temperature range |
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Minimum growth temperature |
the lowest temperature that a microbe can grow at |
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Optimal growth temperature |
the temperature at which the microbe grows best |
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Maximum growth temperature
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the highest temperature that a microbe can grow at |
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Physical Requirements for Microbial Growth - Temperature
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Together, the minimal, optimal & maximal growth temperatures of a microbe are referred to as its: ________ temperatures |
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Microbes can be divided into 3 groups based on their preferred temperature range:
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Psychrophiles (cold-loving microbes) Mesophiles (moderate temp-loving microbes) Thermophiles (heat-loving microbes) |
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Strict psychrophiles
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Psychrotrophs
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cannot grow above 40*C ("food spoilage" microbes) |
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Mesophiles
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optimal growth temp between 25- 40*C |
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What microbes fall into the Mesophiles category? |
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Why do we keep food in the refrigerator?
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- At 0-4*C most ________ microbes cannot survive/grow and food spoilage microbes grow slowly -Above 4*C many bacteria can survive and/or grow |
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Why do we cook food?
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- Slow growth and/or destruction of most types of bacteria (including ______) - Rapid growth of many types of bacteria (including ______) |
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Thermophiles
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heat-loving microbes - optimal growth temperature between 50-60*C many cannot live at temperature below 40*C - Core body temperature is 37*C, so Thermophiles are generally not considered a public health concern. |
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Hyperthermophiles
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have an optimal growth temperature > or = 80*C |
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pH
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potential of hydrogen (H+) |
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If more H+ than OH-
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More acidic ( 0-6ish ) |
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If H+ equals OH-
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= 7 |
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If more OH- than H+ |
More basic ( 8-14ish )
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Examples of certain pH's on a pH scale |
1 - Stomach acid 2 - Lemon juice 3 4 - Wine 4.5 - Tomato juice 5 6 - Urine 6.5 - Milk 7 - Pure water 7.5 - Human blood 8 8.5 - Seawater 9 10 10.5 - Milk of magnesia 11 12 12.5 - Household bleach 13 13.5 - Oven cleaner 14 - Limewater |
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Physical Requirements for Microbial Growth - pH
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For optimal growth of MOST bacteria pH 6.5-7.5 |
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Most ______ bacteria are neutrophiles |
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Acidophiles
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- can survive and grow under acidic conditions - Example - Helicobacter pylori - associated with stomach ulcers and stomach cancer |
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Acidic lake in the Danakil Desert Ethiopia = pH
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pH 1 |
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Acid mine drainage = pH |
pH 5 |
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Alkaliphiles
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- can survive and grow under alkaline/basic conditions - Example - Bacillus alcalophilus - can grow at pH 8-10 |
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Soap Lake, Washington = pH |
pH 9.7 |
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Slag Dumps around Lake Calumet, Illinois = pH |
pH 12.8 |
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Physical Requirement for Microbial Growth - Osmotic Pressure |
- bacteria require H2O for growth - bacteria obtain nutrients dissolved in H2O around them - bacteria are "bags of water" (80-90% H2O) |
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most environments bacteria will encounter will be...
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(especially true for ______) *solute concentration outside the cell is equal to that inside the cell - H2O exchanged equally |
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If solute concentration outside the cell is greater than the solute concentration inside the cell...
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hypertonic environment - water moves out of the cell - plasmolysis occurs - inhibition of growth and/or cell death |
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______ (salt-loving microbes)
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1. Obligate ______
2. Facultative ______ |
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Obligate ______ |
(> or = 20%) for growth and cannot survive at lower salt concentration (e.g., Dead sea bacteria) |
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Facultative ______ |
(e.g., Staphylococcus aureus) |
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Review What is microbial growth? |
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What are the two general of requirements for microbial growth? |
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A bacterium has just encountered a new environment. What are its three basic choices with respect to growth in this new environment? |
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What are a bacterium's cardinal temperatures? Do all bacteria have the same cardinal temperatures? |
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Review Define the following: psychrophiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles. What category do most human pathogens fall into? |
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Defing the following: neutrophils, acidophiles, and alkaliphiles. What category do most human pathogens fall into? |
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With respect to osmotic pressure, what type of environment will most bacteria encounter and what happens under this condition? |
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Review What normally occurs when a bacterium is exposed to a hypertonic environment? How would exposure to this condition affect an obligate halophile or a facultative halophile and why? |
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