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16 terms

Lab Practical 4

STUDY
PLAY
-What type of media will be inoculated in Lab 11?

-Trypticase soy agar
-Mannitol salt agar
-Blood agar
-Chocolate agar
-Phenol red broth
Trypticase soy agar
What will be used to inoculate the plates with the test organisms (Lab 11)?

-sterile bacteriologic loop
-sterile pipette
-sterile swab
sterile swab

Sterile swabs will be used to perform the subcultures. Be sure to use a new sterile swab for each tube, during each subculture.
Which of the following terms describes a microorganism that can SURVIVE exposure to a high temperature, but may not necessarily GROW at a high temperature?

-mesophilic
-hyperthermophilic
-thermophilic
-thermoduric
-thermotrophic
thermoduric

Thermoduric organisms are heat resistant - they can survive exposure to high temperatures, but typically don't grow at those temperatures. Most thermoduric organisms are endospore formers. It is the endospores that enable them to survive the high temperatures. In terms of their growth requirements, most thermoduric microorganisms are mesophilic.
Which of the following will be placed in water baths of various temperatures to provide heat exposure (Lab 11)?

-inoculated plates (petri dishes) of microorganismsEditor
-both broth cultures and inoculated plates will be placed in the water baths
-broth cultures of microorganisms
broth cultures of microorganisms
What temperature will your culture plates (petri dishes) be incubated at after inoculation (Lab 11)?

-It will depend on the temperature assigned to my group.
37C
25C
63C
37C

The organisms used for this lab are mesophiles. We are testing their ability to SURVIVE up to 40 min. exposure to higher temperatures, but upon subculture, the TSA subculture plates are incubated at 37C, their optimum GROWTH temperature.
Why doesn't an acidic stain adhere to bacterial cells?

-Acidic stains have a negatively charged chromogen and are repelled by the positive charges on bacterial surfaces.
-Acidic stains have a positively charged chromogen and are repelled by the negative charges on bacterial surfaces.
-Acidic stains have a positively charged chromogen and are repelled by the positive charges on bacterial surfaces.
-Acidic stains have a negatively charged chromogen and are repelled by the negative charges on bacterial surfaces.
Acidic stains have a negatively charged chromogen and are repelled by the negative charges on bacterial surfaces.
Which of the following is an example of an acidic stain?

-Safranin
-Nigrosin
-Carbol fuchsin
-Methylene blue
Nigrosin
What are the practical advantages of using a negative staining technique?

-Cells retain their natural size and shape
-Cells are not distorted by the effects of chemicals
-Cells are not distorted by the effects of heat
-Cells retain their natural size and shape, and are not distorted by the effects of chemicals or heat.
Cells retain their natural size and shape, and are not distorted by the effects of chemicals or heat.
Why should negatively stained slides be handled with extra precaution?

-The acidic stain is especially toxic.
-Heating a slide makes it more susceptible to breakage.
-The live organisms in the inoculum are not killed with heat fixation.
-The counterstain used is especially toxic.
The live organisms in the inoculum are not killed with heat fixation.
Which of the following statements describes a difference between an acidic stain and a basic stain?

-Heat fixation is recommended when staining with an acidic stain, but not when staining with a basic stain.
-An acidic stain is attracted to bacterial cells; a basic stain is repelled from bacterial cells.
-An acidic stain has a negatively charged chromogen and a basic stain has a positively charged chromogen.
-A basic stain colors the background of the slide; an acidic stain penetrates the cells themselves.
An acidic stain has a negatively charged chromogen and a basic stain has a positively charged chromogen.
Negative stains _________________.

-distort cell shape
-color bacteria
-are heat-fixed
-are viewed without a microscope
-leave bacteria colorless
leave bacteria colorless
The following steps are done to make a negative stain. Which step must be done first?

-The order doesn't matter.
-air-dry
-blot dry
-Take a loopful of nigrosin.
-Take a loopful of bacteria.
Take a loopful of nigrosin.
Which of the following sequences puts the steps of making a negative stain from a broth culture into the correct order?

-Add loop of culture ( Air dry ( Add Nigrosin ( Spread smear
-Add loop of Nigrosin ( Air dry ( Add loop of culture ( Spread smear
-Add loop of culture ( Spread smear ( Air dry ( Add Nigrosin
-Add loop of Nigrosin ( Spread smear ( Add loop of culture ( Air dry
-Add loop of Nigrosin ( Add loop of culture ( Spread smear ( Air dry
Add loop of Nigrosin ( Add loop of culture ( Spread smear ( Air dry
Which of the following microbial structures would be best visualized with a negative stain?

-Fimbriae
-Capsule
-Inclusion bodies
-Ribosomes
-Nucleoid
Capsule
A negatively charged chromophore will NOT stain cells.

-True
-False
True
A negative stain allows you to see structures inside cells.

-True
-False
False