Microscopy

Question 1

what is the smallest object you can see with an objective lens

Answer 1

.3um

Question 2

who invented the gram stain

Answer 2

by the Dutch
physician Hans Christian Gram

Question 3

do Gram-positive retain the crystal violet stain?

Answer 3

bacteria retain the crystal violet
stain because of their thicker cell wall

Question 4

do gram-negative bacteria retain the crystal violet stain

Answer 4

bacteria do not retain the crystal violet stain

Question 5

what is Fluorescence Microscopy used for?

Answer 5

Used to view marine and pathogenic bacteria

Question 6

how does Fluorescence Microscopy work?

Answer 6

The specimen absorbs
light of a defined wavelength, and then emits light of
lower energy, thus longer wavelength; that is, the
specimen fluoresces

Question 7

Excitation and Emission

Answer 7

he specimen absorbs light of a specific wavelength
(the excitation wavelength), then emits light at a
longer wavelength (the emission wavelength)

Question 8

what is a fluorophore

Answer 8

a fluorescent chemical compound
- its cell specificity can be determined in four ways:
- Chemical affinity
- Labeled antibodies
- DNA hybridization
- Gene fusion reporter

Question 9

what did fluorescence microscopy reveal? (this isnt asking about the marine and pathogenic bacteria)

Answer 9

the presence of symbiotic
Bacteroides fragilis bacteria

Question 10

Chemical imaging microscopy

Answer 10

uses mass spectrometry (analysis of
molecular fragments by mass) to visualize the distribution of
chemicals within living cells or microbial communities.

Question 11

what is a high resolution method for chemical imaging

Answer 11

nanoscale secondary ion spectrometry (NanoSIMS)

Question 12

how does nanoscale secondary ion spectrometry (NanoSIMS) work

Answer 12

NanoSIMS combines fluorescence in situ hybridization (FISH)
with mass spectral analysis of bacterial components labeled with
heavy isotopes.
- Allows detailed observation of the gut microbiome

Question 13

which organism is responsible for syphilis

Answer 13

treponema pallidum

Question 14

Phase-Contrast Microscopy

Answer 14

Superimposes refracted light and transmitted light
shifted out of phase

Question 15

what does phase contrast microscopy reveal

Answer 15

• Reveals differences in refractive index as patterns of
  light and dark
• Can be used to view live cells and cellular organelles

Question 16

Electron Microscopy

Answer 16

two major types:
- Transmission electron microscopy (TEM)
- Scanning electron microscopy (SEM)

Question 17

• Transmission electron microscopy (TEM)

Answer 17

• Electrons pass through the specimen
• Reveals internal structures

Question 18

Scanning electron microscopy (SEM)

Answer 18

• Electrons scan the specimen surface
• Reveals external features in 3D

Question 19

The specimens for electron microscopy can be
prepared in several ways

Answer 19

• Embedded in a polymer for thin sections
• Microtome is used to cut slices
• Sprayed onto a copper grid

Question 20

Tomography

Answer 20

In cryo-EM, or electron cryomicroscopy, the
specimen is flash-frozen

Question 21

Cryo-electron tomography, or electron
cryotomography

Answer 21

avoids the need to physically slice
the sample for thin-section TEM

Question 22

Scanning probe microscopy (SPM) enables…

Answer 22

nanoscale observation of cell surfaces

Question 23

what is an example of SPM

Answer 23

The atomic force microscope (AFM)

Question 24

what does the AFM measure

Answer 24

measures the van der Waals forces between
electron shells of adjacent atoms of the cell surface and the sharp tip
-It can be used to observe live bacteria in water or exposed to air (unlike electron microscopy)

Question 25

X-ray diffraction analysis

Answer 25

For samples that can be crystallized, X-ray diffraction makes it possible to fix the position of individual atoms in a molecule

Question 26

example of a model that came out of X-ray diffraction analysis

Answer 26

the anthrax lethal factor
-The model was
encoded in a protein
data bank (PDB)
text file