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Microbio Ch. 3

Test 1

Focal Point focuses light rays at a specific place
Focal length distance between center of lens and focal point
Strength of lens related to focal length
Refraction light bends when passing from one medium to another
Refractive index measure of light bending ability
Purpose of Immersion oil same refractive index as glass so ligth will not bend any further.
white light long wave length & cannot resolve structures less than 0.2 um
Numerical aperture function of the diameter of the objective lens in relation to its focal length
Light Microscope uses visible light to observe specimen; 2 lenses
Bright Field 2 lens, specimen is dark ; bright background; best for non viable stained preps
Darkfield best for living organisms; condenser blocks light from directly entering the objective lens
Phase-Contrast no staining required, study living organisms. Dark against light backgrounnd
Fluorescence use fluorochromes dyes. UV rays. Best for ABs.
Electron best for objects smaller than 0.2um like viruses and cell structures
types of electron microscope Transition and Scannin
TEM uses transmitted electrons to produce an image; light passes through specimen. can be viewed through an eyepiece
SEM only able to see the surface, uses elcetrons reflected from the surface of a specimen to creat image. can only be viewed through a viewing screen
Smear dried preparation of bacterial cells on a glass slide
Heat Fixation smear is fixed on slide to prevent washin away. coagulates bacterial protein, kills microbes
Stain (chemical) organic compound containing a benzene ring + a chromophore(color) and auxochrome(charge) group
basic dye positive ions
acidic dye negative ions
types of basic dyes crystal violet, methylene blue, malachite green,safranin
types of acidic dyes acid fuchsin, eosin, nigrosin
Negative staining used to observe the overall shape size and capsules
types of staining simple, differential, special
Simple staining using 1 dye
differential staining at least 3 chemical reagents
Mordant helps a dye bond more w/ the surface of the cell
Differential staining steps Primary stain, decolorizing agent, counterstain
Primary stain stains entire cell
Decolorizer removes primary stain from certain parts of cells
counterstain contrasting color
Hans Christian Gram developed differential staining procedure
gram staining classifies bacteria into 2 groups
gram staining procedure primary stain(crystal violet), apply iodine, apply alcohol(most important), counterstain(safranin)
gram positive bacterial wall thicker layer of peptidoglycan
gram negative bacterial wall thinner layer of peptidoglycan + layer of LPS as part of cell. remain colorless until counterstained
Beta Lactams more active against gram positive bacteria and less against gram negative as they can't penetrate LPS
Acid-Fast Staining uses used to distinguish Mycobacterium and Nocardia
Acid-fast stain binds strongly to a waxy material in cell wall
Acid-Fast staining procedure carbol fuchsin, wash with acid alcohol, counterstain with methylene blue
Special Stains used to color specific parts of microorganisms
Special staining uses highlights endospores, flagella, capsules
Endopore Staining malachite green, wash, counterstain with safranin
Capsule staining India Ink or nigrosin is used to stain background dark then perform simple stain
Flagella Staining mordant is used to build up diameter then stain with carbol fuchsin it becomes visible under the light microscope
Created by: nani012506