Ch 2 & 3: Microscopy & Laboratory culture of microorganisms
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what are microscopes are used for
magnify an image and increase resolution
What is resolution
ability to distinguish 2 adjacent objects as distinct + separate
Whats the benefit of better resolution
more detail
What is the resolution of the human eye
~100 um
what lense does compound light microscope have
2 lenses - objective + ocular
in compound light microscope, where is the light source focus
focused on the specimen by a condenser
what does resolution depend on
wavelength and light gathering ability of the lens
what does immersion oil do
increase light that enters the lens
how do you find total magnification
objective magnification x ocular magnification
what is a bright field microscope
range of techniques used for illumination of samples in light microscopes
Why are staining dyes used
to increase contrast for bright-field microscope
what is the charge of most dyes
positive charges - theyre basic in nature
how do staining dyes work
dyes are positively charged, they bind to negatively charged cell components (nucliec acids, proteins etc)
what is a differential stain
stain different kinds of cells different colors
most common differential stain
gram stain
gram stain divided bacteria into what groups
gram-positive (purple) Gram - negative (pink)
what do gram stains happen
due to differences in cell wall structures
where are acid fast stains used
used to identify acid fast organisms
What does mycolic acid do
attaches to cell wall surface, producing wax like hydrophobic coating
What color is the initial stain and counterstain
red and bluw
what does initial stain do
penetrates and is retained by mycolic acid (red) , the other cells destain and take up the blue counterstain
what is the best resolution with light microscope
~0.2uM
how are specimens visualized in a bright field microscope
slight differences in contrast between them and the surroundings
Can we see bacterial in a bright-field miscroscope
Typically difficult to see bacterial cells, unless the organisms are pigmented