2: Observing Microorganisms Through a Microscope Flashcards
diameter of most bacteria
0.2 to 2.0 micrometers
diameter of typical human RBC
7 micrometers
spiral-shaped bacterium that is the leading cause of stomach ulcers, chronic inflammation, and resulting stomach cancer
helicobacter pylori
magnification of objectives lenses
low power=10X; high dry=40X; oil immersion=100X
magnification of ocular lens
10X
ability of the lenses of a microscope to distinguish between two separate points a specified distance apart
resolution
Light microscopes cannot resolve structures smaller than____
0.2 micrometers
a measure of the light-bending ability of a medium
refractive index
how does staining bacteria help them be more easily seen?
changes their refractive index relative to the surrounding material
helps reduce undesired refraction because it has the same refractive index as glass
immersion oil
type of microscope used to diagnose syphilis, examine living microbes in liquid suspensions
darkfield microscope.
syphilis
treponema pallidum, corkscrew microbes
permits detailed examination of internal structures of living microbes
phase-contrast microscope
uses two beams of light and prisms thereby adding contrasting colors to the view. similar to phase-contrast microscopy
Differential Interference contrast (DIC) microscopy
employs a UV light source. requires specimen to be tagged with fluorchrome dyes that attach to specific antibodies. very rapid diagnostic test
fluorescent microscopes
what bacterium is responsible for tuberculosis and what type of microscope is used to detect its presence?
Mycobacterium Tuberculosis. fluorescent microscope
fluorescent dyes can be attached to specific antibodies which in turn can be used to label specific microbes
fluorescent antibody technique, or immunofluorescence
specimens are stained with fluorchromes so they emit light, then scanned in fine cross-sectional slices with short-wavelength blue light. computer then contructs 3D complete image
confocal microscopy
chancre
painless ulcer caused by syphilis
can track the activity of living cells in real time
two-photon microscopy
sends sound waves through specimen. can resolve as small as 1 micrometer
scanning acoustic microscopy (SAM)
uses beam of electrons rather than light and uses magnets rather than lenses. resolves smaller than 0.2 micrometers. used to view viruses
electron microscopy
electron microscope that provides only 2D and can magnify up to 100,000X
transmission electron microscope
electron microscope that provides 3D and can magnify up to 10,000X
scanning electron microscope
greater resolving power than electron microscopes and can be used to view molecules, such as DNA
scanning-probe microscopy
simultaneously kills microorganisms and glues them to the slide
fixing
stains the background, not the microbe. give example
negative stain. india ink prep
what stain must be used to visualize cryptococcus neoformans or klebesiella pneumoniae
negative stain/ india ink
often causes marked thickening of the subarachnoid space secondary to the hight mucopolysaccharide content of the organisms wall. at the same time, paucity of acute inflammation results in very little brain swelling. likes to prow in the brain of someone with AIDS. opportunistic.
cryptococcus meningitis
space outside of brain where you find CSF
subarachnoid space
used to visualize cell shape and arrangements only
simple stain
differential stains
gram stain and acid-fast stain
steps to gram stain
crystal violet>gram’s iodine (mordant)>alcohol or acetone alcohol (decolorizing agent)>safranin
gram positive
blue bacteria
how do all fungi (yeasts and molds) gram stain?
gram positive (blue)
gram negative
red bacteria
how do all human cells gram stain?
gram negative (red)
how do mycobacterium gram stain?
gram positive, if at all
“fixes” the gram stain so that it is harder to wash away
gram’s iodine, mordant
used to stain members of the genus mycobacterium
acid-fast stain
steps to acid-fast stain
carbolfuchsin (red dye)> heat> decolorize iwth acid alcohol > methylene blue
acid fast bacteria
red bacteria
non-acid fast bacteria
blue bacteria
how do all human cells acid-fast stain?
non-acid fast (blue)
microbe detected with acid-fast stain that affects the skin and nervous system. is temp sensitive (can’t survive in high temps)
mycobacterium leprae (leprosy)
microbe detected with acid-fast stain that affects the lungs and spreads throughout the body
mycobacterium tuberculosis
preparations for determination of motility
hanging drop or wet mount
what must happen before microbes can be stained?
they must be “smeared” on a slide and “fixed” by gentle heating
