History and Microscopy

Question 1

applications of microbiology

Answer 1

agriculture (N2 fixation, nutrient cycling, animal husbandry)
food (preservation, fermentation, additives)
disease (diagnosis, treatment, presentation)
energy/environment (biofuels, bioremediation, microbial mining)
biotechnology (GMOs, pharmaceuticals, gene therapy)

Question 2

three domains of life

Answer 2

bacteria, archaea, eukarya

Question 3

archaea’s place relative to bacteria and eukarya

Answer 3

archaea and bacteria are prokaryotes, but archaea and eukarya have a more recent common ancestor and are closer to each other

Question 4

archaea is __ domain

Answer 4

the oldest but also the least evolved domain

Question 5

Koch’s first postulate

Answer 5

the microbe is found in all cases of disease, but absent from healthy individuals

Question 6

Koch’s second postulate

Answer 6

the microbe is isolated from the diseased host and grown in pure culture

Question 7

Koch’s third postulate

Answer 7

when the microbe is introduced into a healthy, susceptible host, the same disease occurs

Question 8

Koch’s fourth postulate

Answer 8

the same strain of microbe is obtained from the newly diseased host

Question 9

spontaneous generation experiment

Answer 9

Pasteur, growth medium in a flask connected to the S curve which excludes dust and microbes

Question 10

fixing specimen protocol

Answer 10

spread culture in thin film over slide, dry in air, pass slide through flame to fix

Question 11

simple stain protocol

Answer 11

flood slide with stain, rinse and dry, place drop of oil on slide, examine with 100x objective

Question 12

for Gram staining, G+ cells are ___, while G- cells are ___

Answer 12

purple, pink

Question 13

bacterial shapes

Answer 13

cocci = spheres, bacilli = sticks, rods, vibrios = bent rods

Question 14

what forms can cocci take?

Answer 14

bunches, chains, quartets

Question 15

what forms can bacilli take?

Answer 15

alone, in chains

Question 16

what does Gram stain react with?

Answer 16

thick cell wall

Question 17

what are advantages of staining?

Answer 17

fixes cells to hold in position, reacts with chemical structure of organism, increases absorbance, makes it easier to find in low-contrast conditions

Question 18

types of microscopy in this class

Answer 18

bright-field, dark-field, phase-contrast, fluorescence microscopy, electron microscopy

Question 19

how does bright field microscopy work?

Answer 19

illumination light is transmitted through the sample and the contrast is generated by the absorption of light in dense areas of the specimen

Question 20

how does dark-field microscopy work?

Answer 20

light shines at oblique angle, only light scattered by sample reaches objective, light bounces off object

Question 21

with what specimen would you be most likely to use dark-field microscopy in this class?

Answer 21

flagella, very thin bacteria

Question 22

phase-contrast microscopy

Answer 22

light passes through and around sample, light through sample is refracted, sample appears darker against light background

Question 23

phase-contrast microscopy application example

Answer 23

internal organelles of eukaryotes

Question 24

fluorescence microscopy

Answer 24

fluorophores absorb high-energy light (short wavelengths), emit lower-energy light (long wavelengths), labelling molecules of interest in cell

Question 25

fluorescently labeling molecules examples

Answer 25

DAPI binds DNA, antibody + F binds to specific molecules, labeled nucleotides to DNA, gene fusion like GFP

Question 26

electron microscopy

Answer 26

electrons behave like light waves, high frequency allows high resolution, sample must absorb electrons, samples is coated with heavy metal, electron beam and sample have to be in vacuum, lenses are magnetic fields

Question 27

transmission EM

Answer 27

sample is fixed to prevent protein movement (aldehydes to fix proteins, flash-freezing, microwaves), fixed sample is sliced very thin (microtome), sample is stained with metal

Question 28

transmission EM application

Answer 28

high resolution (ribosomes, flagellar base, strands of DNA), need many slices to determine 3D structure

Question 29

scanning EM

Answer 29

samples is coated with heavy metal; not sliced; retains 3D structure; gives 3D structures; only examines surface of sample

Question 30

visualizing molecules

Answer 30

X-ray crystallography, NMR