BI 234 CH. 7 EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
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BI 234
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BI 234
BI 234 CH. 7 EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Listeria monocytogenes can grow slowly in your fridge, w/ optimum temp range 30 to 37degrees C, what is it?
Psychrotroph
Psychrotrophs are cold-tolerant organisms that can grow at about 0-30°C. These orga...
Listeria monocytogenes can grow slowly in your fridge, w/ optimum temp range
30 to 37degrees C, what is it?
Psychrotroph
Psychrotrophs are cold-tolerant organisms that can grow at about 0-30°C. These
organisms are commonly associated with foodborne illness because they grow at room
temperature as well as in refrigerated and frozen foods. Listeria monocytogenes readily
grow in refrigerated foods and can contaminate meat and fruit to cause food infections.
Psychrophilic
cold loving
Psychrophiles can thrive between about −20°C and 10°C.
Mesophiles
Mesophiles prefer moderate temperatures and tend to grow best around 10-50°C, a
range that includes body temperature.
Thermophiles
heat loving
Thermophiles prefer warm temperatures of roughly 40-75°C
,Your initial inoculum was 200 cells. How many cells would be present after 2
hours if the generation time was 30 minutes?
3200 cells
Prokaryotic cells replicate by binary fission; one parent cell will divide and produce two
identical daughter cells. Therefore, with each generation the number of cells will double.
Your initial inoculum was 200 cells. After one generation, 400 cells would be present,
after two generations 800 cells, after three generations 1,600 cells, and after four
generations, 3,200 cells woud be present in your culture.
Which of the following infectious agents are the most difficult to control with
standard autoclaving methods?
Prions
Infectious proteins called prions can withstand standard autoclaving times and
temperatures. They can, however, be eliminated through a combination of chemical
treatments and increased temperature and pressure during autoclaving.
The enzymes superoxide dismutase and catalase work together to convert
reactive superoxide ions back to _________.
Molecular oxygen
Superoxide dismutase converts reactive superoxide ions to hydrogen peroxide, and
then catalase converts hydrogen peroxide to water and oxygen.
,Which of the following methods would be best for sterilizing a sample of a heat-
sensitive solution?
Filtration
The application of heat would compromise the solution. Liquids can be sterilized using
superfine membrane filters made from a variety of polymers, such as cellulose nitrate
and polyester. Pore sizes can range from 0.1 μm to filter out bacteria and protists to
0.01 μm to remove viruses.
Although Staphylococcus aureus can grow at 7% NaCl, it grows best at NaCl
levels less than 1%. This organism is a __________.
Facultative halophile
Organisms such as Staphylococcus aureus that tolerate higher solute concentrations
but may not grow especially well in them are called facultative halophiles. These
bacteria that thrive on our skin despite salty sweat can withstand solute concentrations
of up to 15%.
Halophiles
"salt-loving"
Some organisms thrive in high-salt environments and are called halophiles. These
microbes tolerate environments that are up to 35% salt and can thrive in places like the
Dead Sea and the Great Salt Lake of Utah.
Neutraphiles
, pH 5-8
They make up the majority of microorganisms known today, especially pathogens.
Mesophiles
moderate temperature loving microbes
Mesophiles prefer moderate temperatures and tend to grow best around 10-50°C.
_________ reduces the number of microbes on a given non-living surface of a
sample.
Disinfection
Disinfection reduces the number of microbes on a given non-living surface of a sample.
Sterilization
Sterilization eliminates all bacteria, viruses, and endospores. It is often required for
drugs, objects used for invasive medical procedures, and for media and glassware used
to culture microbes in a lab.
aseptic technique
Aseptic techniques prevent the introduction of contaminating microbes to a patient, a
clinical sample, or others in the healthcare setting.
Pasteurization
Pasteurization is applied to dairy and other food products to eliminate pathogenic
bacteria. Application of moderate heat well below the liquid's boiling point eliminates
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