History and Microscopy Flashcards
applications of microbiology
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)
three domains of life
bacteria, archaea, eukarya
archaea’s place relative to bacteria and eukarya
archaea and bacteria are prokaryotes, but archaea and eukarya have a more recent common ancestor and are closer to each other
archaea is __ domain
the oldest but also the least evolved domain
Koch’s first postulate
the microbe is found in all cases of disease, but absent from healthy individuals
Koch’s second postulate
the microbe is isolated from the diseased host and grown in pure culture
Koch’s third postulate
when the microbe is introduced into a healthy, susceptible host, the same disease occurs
Koch’s fourth postulate
the same strain of microbe is obtained from the newly diseased host
spontaneous generation experiment
Pasteur, growth medium in a flask connected to the S curve which excludes dust and microbes
fixing specimen protocol
spread culture in thin film over slide, dry in air, pass slide through flame to fix
simple stain protocol
flood slide with stain, rinse and dry, place drop of oil on slide, examine with 100x objective
for Gram staining, G+ cells are ___, while G- cells are ___
purple, pink
bacterial shapes
cocci = spheres, bacilli = sticks, rods, vibrios = bent rods
what forms can cocci take?
bunches, chains, quartets
what forms can bacilli take?
alone, in chains
what does Gram stain react with?
thick cell wall
what are advantages of staining?
fixes cells to hold in position, reacts with chemical structure of organism, increases absorbance, makes it easier to find in low-contrast conditions
types of microscopy in this class
bright-field, dark-field, phase-contrast, fluorescence microscopy, electron microscopy
how does bright field microscopy work?
illumination light is transmitted through the sample and the contrast is generated by the absorption of light in dense areas of the specimen
how does dark-field microscopy work?
light shines at oblique angle, only light scattered by sample reaches objective, light bounces off object
with what specimen would you be most likely to use dark-field microscopy in this class?
flagella, very thin bacteria
phase-contrast microscopy
light passes through and around sample, light through sample is refracted, sample appears darker against light background
phase-contrast microscopy application example
internal organelles of eukaryotes
fluorescence microscopy
fluorophores absorb high-energy light (short wavelengths), emit lower-energy light (long wavelengths), labelling molecules of interest in cell
fluorescently labeling molecules examples
DAPI binds DNA, antibody + F binds to specific molecules, labeled nucleotides to DNA, gene fusion like GFP
electron microscopy
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
transmission EM
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
transmission EM application
high resolution (ribosomes, flagellar base, strands of DNA), need many slices to determine 3D structure
scanning EM
samples is coated with heavy metal; not sliced; retains 3D structure; gives 3D structures; only examines surface of sample
visualizing molecules
X-ray crystallography, NMR
