QUIZ 1 Flashcards
A student completes a Gram stain on a bacterial smear that has a mix of gram-negative and gram-positive organisms. The student stops the procedure without adding safranin. Predict the appearance of the Gram-positive organisms and the Gram-negative organisms.
The gram-positive organisms would appear purple, and the gram-negative organisms would be colorless.
Negative staining is the standard approach used to visualize which structure(s)?
CAPSULES
What is the correct order for the Gram stain process?
crystal violet → iodine → decolorizer → safranin
Which of the following is true of bacterial strains?
They are closely related subtypes within a bacterial species that may or may not have similar properties.
A student is observing a Gram stain with the 100× (oil immersion) lens. The image appears cloudy yand dark. Which of the following actions will NOT increase the clarity of the image?
lowering the stage to increase the distance between the object and the objective lens
All of the following describe a major feature used to classify organisms into to three domains (Bacteria, Archaea, and Eukarya) EXCEPT __________.
presence or absence of DNA
Pasteur discovered that microbes can cause food spoilage. His solution to protect wine from spoiling was a process called pasteurization, which is based on what principle?
heating beer and wine just enough to kill those organisms causing the spoilage
Microorganisms are essential to our life. Each of the following is an example of a beneficial function of microorganisms EXCEPT.
increased number of illnesses.
Microbes that live stably in and on the human body are called the.
human microbiome.
You are performing a Gram stain on gram-negative bacteria and you stop after the decolorizer step. What is the appearance of the bacteria at this point?
colorless
Which of the following are pigments used in microscopy to absorb and reflect light?
Chromophores
Which is the correct order of steps in Gram staining?
crystal violet stain, Gram’s iodine mordant, ethanol decolorization, safranin counterstain
Yeasts are which of the following?
unicellular fungi
Which of the following types of microorganism and its description are NOT correctly matched?
protozoa—small animals
Which of the following indicates how bacteria and viruses typically compare in size?
Bacteria are much larger than viruses.
Which of the following most specifically refers to a stain that dyes a specimen rather than the background?
positive stain
In the Gram stain, what is the purpose of the counterstain
to make gram-negative cells visible
Viruses are not considered living organisms because they?
cannot reproduce by themselves.
Which of the following is true of the microbial world?
Many microbes are helpful.
Simple staining is often necessary to improve contrast in which microscope?
compound light microscope
If you were setting up an experiment to disprove spontaneous generation in a liquid medium, which of the following would be essential to the experiment?
using a sterile liquid and eliminating exposure to microorganisms
Who is credited with first observing cells?
Robert Hooke
Which of the following is the specific name for a stain that colors the background but not the specimen
negative stain
The Gram-staining procedure is best described as which of the following?
differential staining
