ScienceEconomicsExercise 9&11
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Exercise 9&11

Ila Smith avatar Ila Smith
5 April 2023
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18 test answers

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question
how do you know your transfer to a broth was successful? how do you know your transfers to agar slants were successful?
answer
success is presence of growth
question
if any of your transfers were unsuccessful, suggest possible errors that may have been made in transfer process
answer
failure is no growth, growth of wide variety of colonies, signaling contamination
question
provide 3 reasons why in use of aseptic technique essential when handing microbial cultures in lab
answer
limits contamination of yourself and workpalce w/ microbes in cultures, limits contamination of your cultures w/ unwanted environment microbes
question
provide ex of how heat used during inoculation of tube culture
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incinerator used to sterilize loop and used to flame opening of tube after cap removed/ before its replaced
question
How is air contamination prevented when an inoculating loop is used to introduce or take a bacterial sample to/from an agar plate?
answer
hold lid over top of open plate
question
Where should a label be written on an agar plate?
answer
bottom
question
how should agar plates be incubated? why?
answer
inverted position to prevent condensation that would spread inoculated organisms
question
disinfectants are effective against which types of organisms? which types of organisms may remain on lab bench even after disinfection? what disinfectants is used in lab
answer
disinfectants generally useful against vegetative cells and viruses but may not completely eradicate endospores
question
compare and contrast growth of bacteria in diff physical types of media (broths, slants, and agar plates). what might be the advantages and disadvantages of using each type?
answer
presence of growth in liquid (broth) indicated by turbidity/cloudiness. individual colonies not visible and one species couldnt be separated from another. solid (slants) allow for visible growth on surface that can be observed for color/texture. plates allow for isolated colony growth. species can be separated if colonies isolated and subcultured
question
a disinfectant is used on your work surface
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before beginning of lab procedures after all work complete after any spill of live microorganisms
question
To retrieve a sample from a culture tube with an inoculating loop, the cap of the tube is
answer
removed and held w/ fingers of loop hand
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any inoculating loop or needle is sterilized using heat
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until the entire wire is bright red
question
which of the following would be correctly labeled agar plate
answer
S. aureus on bottom
question
noah wanted to transfer Staphylococcus aureus from a broth to agar plate. he picked up broth culture, removed cap, and flamed mouth of tube. he inserted an inoculating loop to obtain bacterial sample. then, he flamed the mouth of the tube and replaced the cap. noah opened lid of labeled agar plate diagonally and used loop to streak surface of agar. after closing lid, he flamed loop in incinerator and put it back in its container. plate was incubated upside down for 24-48 hours. what did noah do wrong in this transfer?
answer
he did not transfer tool correctly
question
how does smear preparation of cells from a liquid medium differ from preparation of cells from a solid medium?
answer
to prepare cells for solid media mix 1 drop of water on slide. 2-3 loopfuls of cells from liquid can be transferred directly to slide
question
why is it important to limit quantity of cells used to prepare a smear?
answer
large amounts of cells in smear can cause staining artifacts b/c staining not washed away from thick areas by destaining agents or water. little bacteria goes along way!
question
describe potential consequences of making smear that is too thick
answer
in differential stains (Gram stain) results can be inaccurate due to trapping of stain in area where smear too thick
question
For preparation of a smear on a slide, what is the purpose of heat fixation? What problems can arise when the slide is heated in a flame?
answer
heat fixation causes cells to adhere to slide during staining. however, structures like capsules can undergo shrinkage during heat fixations and be lost in staining process. for this reason capsule stains not normally fixed