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36 Cards in this Set
- Front
- Back
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An increase in the number of microbial cells in a population is defined as? |
Population Growth |
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The time required for a cell to divide and its population to double is called?
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generation time
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When the number of cells in each generation is expressed as a power of 2, the exponent tells the number of doublings that have occurred this is known as?
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Exponential growth
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What is the bacterial growth curve?
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produced when a population of bacterial cells are grown in a test tube
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What is a "closed culture"?
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When no new nutrients are added to the growth environment |
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Period of little or no cell division is called? |
Lag phase (pre-liminary phase, essential chemicals are created here) |
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Exponential growth phase |
log phase
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period of equilibrium in cell growth |
stationary phase |
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when number of deaths exceeds the number of new cells formed |
Death phase
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A culture that allows maintenance of cell population in exponential phase for long periods |
Continuous culture
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What is the effect of temperature on organism growth? |
Each organism has a set of "cardinal temperatures" |
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What are the three temperature ranges for organisms growth? |
Minimum, Maximum, and Optimum
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Organisms are grouped together by which temperature setting?
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Optimum growth
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Optimum temperatures are marked by what?
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best for metabolic processes, most rapid growth, always closer to maximum than minimum |
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Three primary classifications based on tempertures
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Psychrophiles (cold loving) mesophiles (moderate temp) and thermophiles (heat loving) |
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Two types of psychrophiles |
Obligate and facultative Psychrophiles
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What is a facultative psychrophile |
will function at zero but have a higher optimum temp than obligate
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What is the optimum temp for Mesophiles
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20-40 celesuis |
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Microorganisms capable of growth at high temperatures are called? |
Thermophiles |
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What are thermophiles that love extreme temps called?
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Hyperthermophiles
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Microorganisms usually cause changes in ___ of the enviroment as they grow |
pH
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Which organisms grow at low pH
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Acidophiles
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Culture medium |
nutrients prepared for microbial growth |
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sterile |
no living microbes |
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inoculum |
introduction of microbes into medium |
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culture |
microbes growing in/on culture medium
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agar
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-complex polysaccharide
-used as solidifying agent for culture media in Petri plates, slants, and deeps -generally not metabolized by microbes -liquefies at 100 Celesius -solidifies at ~40 Celesius |
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Chemically defined media |
exact chemical composition is known |
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complex media |
extracts and digests of yeasts, meat or plants -nutrient broth -nutrient agar
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Biosafety levels |
BSL 1: no special precautions BSL 2: lab coat, gloves, eye protection BSL 3: biosafety cabinets to prevent airborne transmission BSL 4: sealed, negative pressure -exhaust air is filtered twice
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differential media |
makes it easy to distinguish colonies of different microbes |
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selective media |
supresses unwanted microbes and encourages desired microbes |
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enrichment culture
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-encourages growth of desired microbe
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pure culture |
contains only one species or strain; streak plate method is used to isolate pure cultures |
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colony |
a population of cells arising from a single cell or spore or from a group of attached cells often called a colony forming unit (CFU)
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methods for measuring microbial growth |
DIRECT METHODS: -plate counts -filtration -MPN -Direct microscopic count
INDIRECT METHODS: -turbidity -metabolic activity -dry weight |
