Exam (elaborations)
Microbiology Lab Exam 1 Questions with Solutions 2024
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Microbiology Lab Exam 1
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Microbiology Lab Exam 1When should hands be washed? - answer Wash your hands thoroughly with soap and
water after handling living microbes and before leaving the laboratory each day. Also,
wash your hands after removing gloves.
How do you clean your lab bench? - answer Wipe the desktop with a disinfectant (e.g.,
Coverage or 10% chlorine bleach) before and after each lab period. Allow disinfectant to
evaporate; do not wipe dry
Why must Bunsen burners and incinerators be treated with caution even after you have
finished using them? - answer It is a fire & safety hazard as well as an additional source
of unnecessary heat in the room
When should you sterilize your loop? - answer Before and after use through Bunsen
burner if BSL-1 or in enclosed electric incinerator if BSL-2 (also, sterile disposable
loops/wooden sticks)
Describe 2 specialized waste containers that can be found in lab: - answer1)
sharps/broken glass container: disposal of broken glass or any other item that could
puncture an autoclave bag
2)autoclave container: disposal of plate cultures and other contaminated non-sharp
disposable items
Describe appropriate attire that should be worn in lab: - answer1) Wear eye protection
whenever heating chemicals
2)Wear disposable gloves while staining microbes and handling blood products
3) Lab coat
4) close-toed toes
Why must electronic devices and other personal items be put away before entering the
lab room and not brought out before fully exiting the room? - answerContamination of
these items can be a health hazard as well as expensive.
What is the protocol if infectious material is spilled? - answerCover any culture spills
with paper towels. Soak the towels immediately with disinfectant and allow them to
stand for 20 minutes. Report spill to the instructor. When you are finished, place towels
in container for autoclaving
,Where should gloves be disposed of? Why? - answerin container designated for
autoclaving/biohazardous waste bin to reduce risk of contamination
The lysis of red blood cells in blood agar is indicative of the presence of which
enzymes? - answerstreptolysin O and S
When looking at a blood agar plate with bacterial growth, beta is complete lysis of the
red blood cells, alpha is partial lysis, and gamma is no lysis. - answerTrue
An organism that obtains its nutrients from dead organic matter is a(n) __________. -
answersaprophyte
A reservoir is - answera source of microbial contamination.
Commensalism is best described as a(n) - answerrelationship between two organisms
where only one member benefits and the other is unharmed.
A pathogen is best described as - answerany microorganism that causes disease.
Staphylococcus bacteria are commonly present in the human nasal cavity but rarely
cause disease of the upper respiratory system. This situation is an example of
(commensalism/mutualism/parasitism). - answercommensalism
Normal microbiota may cause disease if conditions change in the body. - answerTrue
It has been determined that the temperature in an autoclave should reach __________
for sterilization. - answer121 degrees Celsius (and 15 psi for 15 minutes to sterilize
small volumes) (
What role does pressure play in an autoclave? - answerPressure is applied to boiling
water to prevent heat from escaping as steam (Adding pressure to boiling water leads to
higher water temperatures.)
How do scientists ensure that autoclaved materials were actually sterilized? -
answerThey may place a sterility indicator with a special dye to detect the growth of
endospores. ( Some sterility indicators have dyes that change color in the presence of
living bacteria, indicating that the correct sterilizing temperature and time have not been
reached.)
What is the purpose of an autoclave? - answerto sterilize equipment and media
Autoclaves are used to ensure that equipment and media are sterile, or free of
contamination
Where are you likely to find an autoclave? - answerin a dentist office
, Why is autoclaving rather than boiling water used for sterilization? - answerBoiling water
does not kill everything, including bacterial endospores and some protozoan cysts.
Boiling water reaches a maximum temperature of 100 degrees Celsius, compared with
autoclaving where the temperature reaches at least 121 degrees Celsius. Boiling water
is not hot enough to kill endospores or cysts in a reasonable amount of time.
Why do containers of liquid placed in an autoclave need to remain at least slightly
open? - answerIf they remain closed, they may implode.
The extreme temperature and pressure changes within the autoclave may cause closed
containers to implode.
Why are endospores sometimes used in sterility indicators? - answerThey are the
hardest life form to kill.
If an autoclave kills endospores within a sterility indicator, it is safe to assume that
everything else is sterilized.
Which of the following are the parameters for autoclaving? - answer15 minutes at
121°C and15 psi
In general, moist heat kills microorganisms in less time than dry heat. - answerTrue
Which of the following lists microbes or microbial structures in order from the hardest to
destroy by heat to the easiest to destroy? (4 total) - answerbacterial endospores, fungal
spores, vegetative bacteria, fungi
Which of the following techniques can be used to sterilize microbiological media? -
answerautoclaving
Why are endospores used to measure the effectiveness of autoclave sterilization? -
answerEndospores are very hard to kill
To solidify media used to grow microbes, usually __________ is added to the nutrient
broth. - answeragar
The growth resulting in the elevation of a bacterial colony is due to the colony growth
spreading vertically as well as horizontally. - answerTrue
A colony on an agar plate that is slightly and equally elevated and unbroken would be
classified as ___________________ - answera raised, circular colony.
The growth characteristics of a bacterial culture streak on an agar slant will not be the
same as if the streak were on an agar plate. - answerFalse
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