Chapter 3 Flashcards
Acid-fast Mycobacteria differ from non–acid-fast bacteria by the presence of \_\_\_\_\_\_\_\_\_\_. flagella capsules endospores peptidoglycan waxy material in their cell walls
waxy material in their cell walls
Which of the following statements is NOT true for both TEM(transmitted electrons) and SEM(scattered electrons)?
The illuminating source is an electron beam.
Black-and-white images are produced.
Both can be used to view specimens smaller than 0.2 micrometers.
The specimen must be sectioned before viewing.
The microscope is focused using electromagnetic lenses.
The specimen must be sectioned before viewing
Bacterial cells have an overall negative charge on their surface. If a bacterial smear is stained by a pink, acidic, water-soluble stain and then washed with water, which of the following describes the result that will be observed when viewing the stained slide under a microscope? unstained cells with no background unstained cells in a pink background pink cells in a pink background pink cells purple cells
unstained cells with no background
In a negative staining procedure, the bacterial cells would appear __________ when viewed under a microscope.
the same color as the background and thus not easily observed
stained in an unstained background
brightly colored in a contrasting background
attracted to the dye used in the staining procedure
unstained in a colored background
unstained in a colored background
In the capsule stain using India ink, capsules are distinguished as \_\_\_\_\_\_\_\_\_\_ surrounding cells. green shadows clear halos pink circles purple rims blue extensions
clear halos
In the Gram stain, crystal violet is the \_\_\_\_\_\_\_\_\_\_. primary stain decolorizing agent fixative mordant counterstain
Primary stain
In the Gram stain, crystal violet remains in gram-positive cells after treatment with alcohol because crystal violet–iodine (CV–I) complexes are trapped \_\_\_\_\_\_\_\_\_\_. in mycolic acid by endospores in thick layers of peptidoglycan in the outer membrane by flagella
in thick layers of peptidoglycan
In the Gram stain, if the decolorizing step is deleted, gram-negative cells will appear \_\_\_\_\_\_\_\_ at the completion of the staining procedure. blue unstained green pink purple
purple
In the Gram-stain procedure, a clear oval in the center of a cell could indicate \_\_\_\_\_\_\_\_\_\_. an unstained nucleus the unstained bacterial chromosome a capsule lack of the central nucleoid the presence of an endospore
the presence of an endospore
Resolution is very good when using an electron microscope because the \_\_\_\_\_\_\_\_\_\_ of the electron beam is much shorter than that of visible light. wavelength reflection penetration absorption frequency
wavelength
The \_\_\_\_\_\_\_\_\_\_ charge of a basic dye adheres to the \_\_\_\_\_\_\_\_\_\_ charge of bacterial cell surfaces. positive; acidic negative; positive positive; basic negative; acidic positive; negative
Positive; negative
Which of the following steps is common to both the Gram stain and the acid-fast stain? the application of iodine as a mordant steam exposure for stain penetration the use of methylene blue as a counterstain heat fixation of the smear before staining acid-alcohol for decolorizing
heat fixation of the smear before staining
Which of the following kinds of microscopy would be most appropriate for viewing the shape and arrangement of pili or fimbriae on the surface of a bacterial cell? darkfield microscopy phase-contrast microscopy brightfield microscopy scanning electron microscopy transmission electron microscopy
Scanning electron microscopy
Which of the following types of microscopy can be used to specifically identify pathogens (such as Mycobacterium tuberculosis or rabies virus) in specimens? fluorescence transmission electron darkfield phase-contrast brightfield
Fluorescence
Which of the following types of microscopy is most useful for viewing the internal structures of unstained specimens? phase-contrast confocal fluorescence brightfield electron
phase-contrast
