Chapter 6: Microbial Growth

Classify microbes into five groups on the basis of preferred temperature range.
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Classify microbes into five groups on the basis of preferred temperature range.
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Identify how and why the pH of culture media is controlled.
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Explain the importance of osmotic pressure to microbial growth.
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Name a use for each of the four elements (carbon, nitrogen, sulfur, and phosphorus) needed in large amounts for microbial growth.
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Explain how microbes are classified on the basis of oxygen requirements.
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Identify ways in which aerobes avoid damage by toxic forms of oxygen.
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The requirements for microbial growth can be divided into 2 categories:
________: temperature, pH, osmotic pressure
________: carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements, organic growth
physical, chemical
Microorganisms are classified into 3 primary groups based on their preferred temperature range: _____________, __________, and ___________.
psychrophiles, mesophiles, thermophiles
organisms that grow best between 15-20C; cold loving microbe
psychrophiles
organisms that grow between 10-50C; moderate-temp loving microbe
mesophiles
organisms that grow optimally between 50-60C; heat loving microbethermophileBacterial species can grow at particular _______, _______ and _______ temperatures.minimum, optimum, maximumThe lowest temperature at which a species will growminimum growth temperaturethe temperature at which a species grows bestoptimum growth temperaturethe highest temperature at which a species can growmaximum growth temperaturebacteria that cause food spoilagepsychrotrophsheat resistant thermophilic bacteria that survive extremely hot environmentsendosporesorganisms that have optimum growth temperatures of 80C; extreme thermophilehyperthermophilethe acidity or alkalinity of a solutionpHbacteria that grows below pH 4; tolerant of acidityacidophilesloss of water from a cell in a hypertonic environmentplasmolysisan organism that requires high osmotic pressures such as high concentrations of NaCl.obligate halophilean organism capable of growth in, but not requiring 1-2% saltfacultative halophilethe use of gaseous nitrogen directly from the atmospherenitrogen fixationa chemical element required in small amounts for growthtrace elementan essential organic compound that an organism is unable to synthesizeorganic growth factora microbial community that usually forms as a slimy layer on a surfacebiofilmsWas is the temperature range bacteria can grow in (in C)?-10 to 110only aerobic growth; oxygen requriedobligate aerobeboth aerobic and anaerobic growth; greater growth in the presence of oxygenfacultative anaerobesonly anaerobic growthobligate anaerobesexact chemical composition is known; fastidious organism are those that require many growth factorschemically defined mediamicrobes that require high CO2 levelscapnophileBiosafety level that has no special precautions, used in basic teaching labsBSL-1Media that suppresses unwanted microbes and encourages desired microbes; contained inhibitors to suppress growthselective mediaallow distinguishing of colonies of different microbes on the same plate; has selective and differential characteristicsdifferential mediausually a liquid that encourages the growth of a desired microbe by increasing very small numbers of a desired organism to detectable levelsenrichment culturea population of cells arising from a single cell or spore or from a group of attached cellscolonymethod used to isolate pure culturesstreak plate methodCFU: No. of bacteria/ml = No. of cells counted/ V of area countedDeep freezing takes place between ___ to ___C.-50 to -95time required for a cell to divide (20 minutes to 24 hours)generation timeBinary fission _______ the number of cells of each generation.doublesWhat are the phases of growth?Lag, Log, Stationary, and Death phaseintense acivity preparing for population growth, but no increase in populationlag phaselogarithmic, or exponential increase in populationlog phaseperiod of equilibrium, microbial deaths balance production of new cellsstationary phasepopulation is decreasing at a logarithmic ratedeath phasemeasurement of cloudiness with a spectrophotometerturbidity