Observing Microorganisms Through A Microscope: Lectures Prepared by Christine L. Case
Observing Microorganisms Through A Microscope: Lectures Prepared by Christine L. Case
Observing Microorganisms Through A Microscope: Lectures Prepared by Christine L. Case
Observing
Microorganisms
Through A
Microscope
Acid-fast staining of a
patient’s sputum is a
rapid, reliable, and
inexpensive method to
diagnose tuberculosis.
What color would
bacterial cells appear if
the patient has
tuberculosis?
Learning Objectives
3-1 List the metric units of measurement that are
used for microorganisms.
1 µm = 10–6 m = 10–3 mm
1 nm = 10–9 m = 10–6 mm
1000 nm = 1 µm
0.001 µm = 1 nm
Learning Objectives
3-2 Diagram the path of light through a compound
microscope.
3-3 Define total magnification and resolution.
In a compound
microscope, the image
from the objective lens
is magnified again by
the ocular lens
Total magnification =
objective lens ocular
lens
Learning Objectives
3-4 Identify a use for darkfield, phase-contrast,
differential interference contrast, fluorescence,
confocal, two-photon, and scanning acoustic
microscopy, and compare each with brightfield
illumination.
3-5 Explain how electron microscopy differs from light
microscopy.
3-6 Identify one use for the TEM, SEM, and scanned-
probe microscopes.
Accentuates diffraction
of the light that passes
through a specimen
Uses UV light
Fluorescent
substances absorb UV
light and emit visible
light
Cells may be stained
with fluorescent dyes
(fluorochromes)
Measures sound
waves that are
reflected back from
an object
Used to study cells
attached to a
surface
Resolution 1 µm
Ultrathin sections of
specimens
Light passes through
specimen, then an
electromagnetic lens,
to a screen or film
Specimens may be
stained with heavy
metal salts
An electron gun
produces a beam of
electrons that scans
the surface of a
whole specimen
Secondary electrons
emitted from the
specimen produce
the image
1,000–10,000; resolution 20 nm
ANIMATION Staining
Color of Color of
Acid-fast Non–Acid-fast
Acid-fast staining of a
patient’s sputum is a
rapid, reliable, and
inexpensive method to
diagnose tuberculosis.
What color would
bacterial cells appear if
the patient has
tuberculosis?
Cells stained
Negative stain
Mordant on flagella
Carbolfuchsin simple stain