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135 Cards in this Set
- Front
- Back
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Above ~65°C, only _____ life forms exist |
prokaryotic
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_____ are organisms with growth temperature optima between 45°C and 80°C |
Thermophiles
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____ are organisms with optima greater than 80°C |
Hyperthermophiles
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Hyperthermophiles in hot springs are what type based on energy utililation? |
Chemoorganotrophic and chemolithotrophic |
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______ (Prokaryotes/Eukaryotes) are able to grow at higher temperatures than _______ (Prokaryotes/Eukaryotes) |
Prokaryotes Eukaryotes |
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_____ (nonphototrophic/phototrophic) organisms can grow at higher temperatures than ______ (nonphototrophic/phototrophic) organisms |
nonphototrophic phototrophic |
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For enzyme and proteins to function optimally at high temperatures, what features provide thermal stability? |
1. Critical amino acid substitutions in a few locations provide more heat-tolerant folds 2. An increased number of ionic bonds between basic and acidic amino acids resist unfolding in the aqueous cytoplasm |
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What are the modifications in cytoplasmic membranes that ensure heat stability? |
1. Bacteria have lipids rich in saturated fatty acids2. Archaea have lipid monolayer rather than bilayer |
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Organisms with the highest temperature optima are _______ (Bacteria/Archaea) |
Archaea |
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Organisms that grow best between pH 6 and 8 |
Neutrophiles
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____ are organisms that grow best at low pH (<6)
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Bacteria that are ________have membranes destroyed at neutral pH. |
obligate acidophiles
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Some halophilic alkaliniphiles have ________ rather than proton motive force
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sodium motive force |
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Microbial culture media typically contain ______ to maintain constant pH |
buffers
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______ is defined as ratio of vapor pressure of air in equilibrium with a substance or solution to the vapor pressure of pure water |
Water activity (aw): water availability
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Typically, the cytoplasm has a _____ (lower/higher) solute concentration than the surrounding environment, thus the tendency is for water to move _____ (into/out of) the cell. This is a _______ (positive/negative) water balance. |
higher into positive |
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When a cell is in an environment with a higher external solute concentration, water will flow _______ (in/out) unless the cell has a mechanism to prevent this. |
out |
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_____ are organisms that grow best at reduced water potential; have a specific requirement for NaCl |
halophiles
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_____ are organisms that require high levels (15–30%) of NaCl for growth |
extreme halophiles
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_____ are organisms that can tolerate some reduction in water activity of environment but generally grow best in the absence of the added solute |
Halotolerant
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____ are organisms that live in environments high in sugar as solute
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Osmophiles
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____ are organisms able to grow in very dry environments |
Xerophiles |
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How does a cell increase the internal solute concentration? |
1.Pumping inorganic ions from environment into cell 2.Synthesis or concentration of organic solutes |
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_____require oxygen to live |
Strict Aerobes
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______do not require oxygen and may even be killed by exposure |
Strict Anaerobes
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_______ use oxygen when available but can live without oxygen |
Facultative aerobes
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______can tolerate oxygen and grow in its presence even though they cannot use it |
Aerotolerant anaerobes
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____can use oxygen only when it is present at levels reduced from that in air |
Microaerophiles |
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______ are chemicals that may be added to culture media to reduce oxygen
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Reducing agents |
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_____ is a complex medium that separates microbes based on oxygen requirements
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Thioglycolate broth
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____ are organisms that grow best at high pH (>9)
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Alkaliphiles
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Turbidity is most often measured with a spectrophotometer and measurement referred to as ______ |
optical density (O.D.)
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What are the advantages of turbidity methods? |
1.Quick and easy to perform2.Typically do not require destruction or significant disturbance of sample
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What are the disadvantages of turbidity methods? |
1.Sometimes problematic (e.g., microbes that form clumps or biofilms in liquid medium) 2. Dead bacteria are counted |
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_______ are the minimum, optimum, and maximum temperatures at which an organism grows |
Cardinal temperatures |
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____ are organisms that grow at midrange temperature |
Mesophile
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___ are organisms with cold temperature optima that inhabit permanently cold environments |
Psychrophiles
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____ are organisms that can grow at 0ºC but have optima of 20ºC to 40ºC |
Psychrotolerant
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Bacteria growing at low temperature have modified cytoplasmic membranes with high _________ fatty acid content |
unsaturated
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Bacteria growing at high temperature have modified cytoplasmic membranes with high _________ fatty acid content
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saturated
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What are the modifications of enzymes structure found in bacteria at low temperatures? |
1. More alpha helices than beta sheets 2. More polar and less hydrophobic amino acids 3. Fewer weak bonds 4. Decreased interactions between protein domains |
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Why are microscopic counts sometimes unreliable? |
1.Cannot distinguish between live and dead cells without special stains 2.Small cells can be overlooked 3.Precision is difficult to achieve 4.Phase-contrast microscope required if a stain is not used 5.Cell suspensions of low density (<106 cells/ml) hard to count 6.Motile cells need to immobilized7.Debris in sample can be mistaken for cells |
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_______ is a method of counting bacteria that uses laser beams, fluorescent dyes, and electronics |
flow cytometer |
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A measurement of living, reproducing population is a _______ |
Viable cell count
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What are the two main ways to perform plate counts?
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1.Spread-plate method 2.Pour-plate method |
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Why can plate counts be highly unreliable when used to assess total cell numbers of natural samples (e.g., soil and water)?
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Selective culture media and growth conditions target only particular species
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Why do direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates?
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1. Microscopic methods count dead cells whereas viable methods do not 2. Different organisms may have vastly different requirements for growth |
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What can effect the accuracy of plate count results? |
1. Culture media used 2. Incubation conditions 3. Duration of growth 4. Plating errors |
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Colony Forming Unit (CFU) is usually one _________ bacteria.
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Viable
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What is the relationship between bacterial counts, OD and turbidity? |
higher bacteria = higher light scattering (higher OD) = higher turbidity |
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What is considered to be the number (range) of countable colonies?
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30-300 |
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Bacterial ______ is an increase in the number of cells
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Growth |
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___ is cell division following enlargement of a cell to twice its minimum sizeBinary fission
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____ is the time required for microbial cells to double in number
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Generation time |
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Generation time is dependent on ___ and ____ |
growth medium incubation conditions |
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____ is growth of a microbial population in which cell numbers double within a specific time interval |
Exponential growth |
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In the formula for exponential growth, ___ is the symbol for final cell number. |
N
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In the formula for exponential growth, ___ is the symbol for initial cell number |
No
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In the formula for exponential growth, ___ is the symbol for the number of generations during the period of exponential growth |
n
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The formula for generation time (g) of the exponentially growing population is _____
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g = t/n
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In the formula for generation time (g), _____ is the duration of exponential growth
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t
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In the formula for generation time (g), _____ is the number of generations during the period of exponential growth
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n
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____ is a closed-system microbial culture of fixed volume
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Batch culture
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During the bacterial growth curve, ______ is the Interval between when a culture is inoculated and when growth begins.
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Lag phase |
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During the bacterial growth curve, ______ is the time rapid of logarithmic growth. |
Exponential phase |
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Cells in the _______ phase are typically in the healthiest state
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Exponential
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During the bacterial growth curve, the ______ phase is when the growth rate of population is zero |
Stationary |
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Why does bacterial die off occur in a culture? |
1. essential nutrient is used up 2. waste product of the organism accumulates in the medium |
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If incubation continues after cells reach stationary phase, the cells will eventually enter ________
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Death phase
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_____ is an open-system microbial culture of fixed volume
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Continuous culture
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In a chemostat, both ______ and _______of culture can be controlled independently and simultaneously |
growth rate population density |
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_____ is the rate at which fresh medium is pumped in and spent medium is pumped out |
dilution rate |
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In a chemostat, the growth rate is controlled by _____
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dilution rate |
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The growth yield (cell number/ml) is controlled by the concentration of the ______ |
limiting nutrient
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In a batch culture, too ____ (low/high) a dilution rate, the organism is washed out.
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High |
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In a batch culture, too ____ (low/high) a dilution rate, the cells may die from starvation |
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Increasing concentration of a limiting nutrient results in _____ (lesser/greater/same) biomass but ____ (lesser/greater/same) growth rate |
greater same |
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A _____ is the most common type of continuous culture device |
chemostat
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What is the formula used to calculate final microbial count given initial number of microbes and generation time? |
N=No2^n |
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Most bacteria have ____ (shorter/longer) generation times than Eukaryotes. |
shorter |
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What modification of the plasma membrane allows some bacteria to live in a cold environment? |
Bacteria have lipids rich in unsaturated fatty acids |
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Are Prokaryotes or Eukaryotes better adapted to life at high temperatures? |
Prokaryotes |
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____ is the killing or removal of all viable organisms within a growth medium
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Sterilization
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____________ is a method of killing C. botulinum endospores in food
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Commercial sterilization
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____ is the treatment of an object to make it safe to handle
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Decontamination
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___ is the absence of significant contamination
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Asepsis
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___ is removing pathogens from living tissue
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Antisepsis
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____ is the killing or removal of all viable organisms within a growth medium
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Sterilization
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___ is removing microbes from a limited area
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Degerming
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____ is the removal of microbes to meet public health standards
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Sanitization
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____ is the suffix that means inhibitory action.
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Static
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_____ delays spoilage of food or other perishable products.
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Preservation
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_______is the most widely used method of controlling microbial growth
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Heat sterilization
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Some bacteria produce heat resistant cells called ______
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endospores
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What are the temperature and times for sterilization in a hot air oven?
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170oC for 2–3 hours without circulation 170oC for 1–1.5 hours with circulating air |
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T/F Boiling at 100oC will not sterilize.
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true
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What is the time, temperature and pressure for the sterilization of liquids in an autoclave?
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121oC 15 min. 15lb/in2
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What is the time, temperature and pressure for the sterilization of instruments in an autoclave?
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121oC 45 min. 15 lb/in2
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What is the time, temperature and pressure for the flash sterilization of instruments in an autoclave?
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135oC 3 min. 30 lb/in2
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Temperature and times used in canning are designed to kill Clostridium botulinum endospores at a concentration of 1,000,000,000,000
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Commercially sterile
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___ is the moderate heating to reduce numbers of spoilage organisms and pathogens without altering taste.
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pasteurization
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Time and temperature used for (HTST) high–temperature–short–time
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72oC 15 seconds
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Time and temperature used for (LTLT) low–temperature–long–time
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63oC 30 min |
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Time and temperature used for (UHT) ultrahigh–temperature |
140oC 4 sec 149oC .5 sec |
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Straining liquids or air through membranes with small pores
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Filtration
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Most bacteria are removed by filtration using ________ pore filters
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.2–.4 μm
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All bacteria and viruses are removed by filtration using ____________ pore filters
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.01 μm |
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High efficiency particulate air filter pore size
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.3 μm
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_______is the process of using precisely controlled heat to reduce the microbial load in heat–sensitive liquids
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Pasteurization
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____ is non–ionizing radiation
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UV
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Amount of energy required to reduce viability tenfold is analogous to the _____ for heat.
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D value |
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_______ avoids the use of heat on sensitive liquids and gases
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filtration
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______ filters function more like a sieve
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membrane
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What membrane filter pore size will remove all microbes & viruses?
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0.01 micrometer
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_____ refers to microbial contamination
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sepsis
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____ techniques prevent microbial contamination of wounds
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Aseptic surgery
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____ is the suffix that means killing action
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cidal
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Minutes to kill 90% of a population at a given temperature
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Decimal Reduction Time (DRT)
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What are three types of dry heat commonly used? |
1.Flaming 2.Incineration 3.Hot–air sterilization |
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_____ organisms are capable of surviving the high heat of pasteurization. |
Thermoduric
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Commercial sterilization is a _____D treatment because it kills kills ______ endospores |
12 1,000,000,000,000 |
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__________ radiation has sufficient energy to directly cause modifications and breaks in DNA |
UV |
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UV _____ (can/cannot) penetrate solid, opaque, or light–absorbing surfaces
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cannot
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_____ damages DNA by forming thymine dimers
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UV
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____ is electromagnetic radiation that produces ions and other reactive molecules
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ionizing radiation
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What are the three common forms of ionizing radiation commonly used?
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X rays gamma rays electron beams |
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Ionizing radiation _____ (can/cannot) penetrate solid, opaque, or light–absorbing surfaces
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can
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_____ filters are used for high volumes (air)
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depth filters
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Antibacterial agents can be classified as ___, ____ or _____ depending on how they work.
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bacteriostatic, bacteriocidal, bacteriolytic
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Agents that reduce microbial numbers to a safe level in the food industry are _____
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sanitizers |
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_____ is the smallest amount of an agent needed to inhibit growth of a microorganism |
Minimum inhibitory concentration (MIC) |
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____ is a means of testing an antimicrobial agent using filter paper discs.
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Disc diffusion assay
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When doing the disc diffusion assay, the area of no growth around a filter paper disc is called____
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Zone of inhibition |
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___ directly targets the removal of all pathogens but not necessarily all microorganisms. |
disinfection |
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Cells in the _______ phase are most vulnerable to killing. |
exponential |
