Exam 2 Flashcards
Most bacteria have a rigid cell wall containing ________ that is responsible for maintaining the bacterial shape under a variety of osmotic conditions.
a. Ribonucleic Acid
b. Peptidoglycan
c. Anions
d. Aniline
b. Peptidoglycan
True or False:
The stains used on February 27 bind to the cell components because the stain is negatively charged
False
How long do you flood the slide with crystal violet?
a. 30 seconds
b. 10 minutes
c. 5 seconds
d. 1 minute
d. 1 minute
What is the purpose for adding the 95% alcohol to the slide?
a. To fix the stain
b. To stain gram negative cells
c. To decolorize (remove crystal violet from) the Gram-negative cells
d. There is no reason for this; it is just an extra step
c. to decolorize (remove crystal violet from) the Gram-negative cells
True or False:
The Gram stain is considered a simple stain.
False
True or False:
February 27th you worked with a mixed broth culture containing Escherichia coli, Staphylococcus epidermidis, and Serratia marcescens.
True
True or False:
Our microbiota is an important mechanism for limiting pathogenic microorganisms on our bodies.
True
The purpose of Streaking for isolation is to
a. Obtain isolated colonies
b. Make a mixed culture
c. Get a layer of growing cells covering the full surface of the plate medium
d. None of the above
a. Obtain isolated colonies
True or False:
One of the objectives in the lab on February 27 was to culture and study the microbiota of the human mouth
True
Our “blank” used for the spectrophotometer on March 6th was:
a. Water
b. Sterile medium
c. Undiluted broth culture
d. Clean empty spectrophotometer tube
b. Sterile medium
True or False:
When making serial dilutions there is no need to used accurate volume measurements
False
You have three plated from a serial dilution that were incubated. Plate A has 356 colonies, plate B has 6 colonies, and plate C has 128 colonies. Which plate(s) do you use to find the viable cell count?
a. Plate A
b. Plate B
c. Plate C
d. Plates A & B
c. Plate C
What temperature does the agar solidify at?
a. 100 degrees Celsius
b. 45 degrees Celsius
c. 15 degrees Celsius
d. 0 degrees Celsius
b. 45 degrees Celsius
CFU stands for…
a. Common Fungal Units.
b. Colony Forming Units.
c. Coliform Feeding Units
d. Campibacter Forming Units
b. Colony Forming Units
True or False:
Another term for Optical Density is Absorption.
True
Serial Quantitative Dilution
a. Mixing equal portions of microbial culture broth and water at once
b. Counting the microbes found in a agar plate
c. Counting the number of CFUs with fluorescing antigens
d. Diluting a culture sample into smaller and smaller concentrations, until you can count the number of CFUs.
d. Diluting a culture sample into smaller and smaller concentrations, until you can count the number of CFUs.
An objective of lab on March 6th was to:
a. Calculate the number of live bacteria from the original, undiluted broth culture.
b. Calculate the number of dead cells in the original, undiluted broth culture
c. Determine how much water is used in order to get a 0 O.D. reading in the spectrophotometer
d. To determine the ratio of live cells compared to dead cells in the media
a. Calculate the number of live bacteria from the original, undiluted broth culture.
An Autoclave is used
a. As a timer
b. To routinely sterilize medium and biohazardous garbage
c. To count the number of colonies growing on a medium
d. As an incubator
b. To routinely sterilize medium and biohazardous garbage
What temperature will the steam reach in the Autoclave?
a. 121-123 degrees Celsius
b. 98-100 degrees Celsius
c. 250-275 degrees Celsius
d. 150-155 degrees Celsius
a. 121-123 degrees Celsius
True or False:
The word ‘sterile’ means that no living organisms are present.
True
On March 20th when we were transferring bacteria from the original broth culture to the sterile TSB tubes, we had to transfer:
a. No more than a single loop full
b. Two loops full
c. 3 microliters via micropipette
d. Just enough, by pouring, to make the TSB turbid
b. two loops full
To test whether the autoclaving was successful in sterilizing material, we place an envelope of _____ in with a load that is being autoclaved.
a. Bacillus stearothermophilus endospores
b. Bacillus stearothermophilus vegetative (growing) cells
c. Bacillus stearothermophilus toxins
d. A plate of very concentrated Bacillus stearothermophilus cells
a. Bacillus stearothermophilus endospores
True or False:
The autoclave allows us to use higher temperatures for sterilization through the use of pressure.
True
True or False:
Dry heat penetrates more efficiently than moist heat.
False
