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BIO205 - Ch 3 -Observing Microorg. Through Microscope - RioSalado - AZ

Quiz yourself by thinking what should be in each of the black spaces below before clicking on it to display the answer.

Micrometer   10^-6 m  
prefix micro   Means unit following should be divided by 1 million  
nanometer (nm)   10^-9 m  
Quorum   Ability of bacteria to communicate & coordinate behavior - group comes together, secrete "inducer" that changes behavior.  
In compound microscope, light rays from an __ pass through a __ that has lenses to direct rays.   illuminator, condenser  
Lenses closest to specimen   objective lenses  
eyepiece   occular lenses  
How is total magnification of compound light microscope calculated?   Objective lense magnification (power) times the ocular lense magnification (power).  
Resolution   Resolving power - ability of lenses to distinguish fine detail & structure - distinguish 2 points a specific distance apart.  
The __ the wavelength of light, the greater the resolution.   shorter  
The white light in compound light microscope has __ wavelength.   long - cannot resolve smaller than 0.2 micrometer  
Max magnification of compound light microscope.   2000x  
Refractive index   Measure of light-bending ability of a medium.  
How do you change refractive index of specimens?   By staining them - they will then have different refractive indexes.  
Immersion oil has same __ as glass.   refractive index - keeps light rays from refracting as they enter air - increases resolving power of lenses.  
Brightfield illumination   Uses visible light for illumination - white background.  
Darkfield microscope   Used for invisible microorganisms & cannot be stained - uses darfkield condenser with opaque disk - sees only reflected light - black background.  
Phase-contrast microscope   Good to examine interior cell structures - Used with living microorganisms - don't have to fix them - uses special condenser to absorb refracted light & interference patterns.  
Differential interference contrast (DIC) microscopy   Measures differences in refractive indexes - 2 beams of light split by prisms & add contrasting colors - higher resolution - 3D.  
Fluorescense   Ability of substances to absorb short wavelengths (ultraviolet) & give off longer length (visible) - glowing  
Fluorescence microscopy   Organism stained with dye to glow (fluorochromes) & viewed under ultraviolet light against dark background.  
Principal use of fluorescence microscopy   FA - fluorescent - antibody technique/immunoflorescence - can detect bacteria, etc w/in cells by viewing if specific antibodies attach.  
Confocal microscopy   3D image made by light microscope - uses fluorescent stains & laser - computer constructs image from stack of images - ATP & Ca ion concentrations.  
Scanning Acoustic Microscopy (SAM)   Evaluates sound waves sent through specimin - used to study living cells attached to another surface - cancer cells, artery plaque, & biofilms.  
What feature of confocal microscopy eliminates blurring?   Use of pinhole aperture  
Principal use of SAM   Study living cells attached to another surface - cancer, plaque, etc.  
Images produced by electron microscope are always __.   in black & white  
2 types of electron microscope.   Transmission - thin sections of a specimen & scanned - 3d view of surface.  
Positive staining   Salts of various heavy metals used as stains & fixed onto specimens.  
Negative staining   Increase electron opacity of surrounding field & useful when studying very small particles/specimins like virus particles, bacterial flagella, proteins.  
Shadow casting   Heavy metals adhere at 45 degree angle on one side & leaves a shadow to crate 3d for size.  
TEM has __ resolutions & valuable for examining __ of specimen.   high - layers  
Drawback of TEM?   Only thin specimens - kills specimen & causes shrinking & distortion - artifacts.  
Scanning Electron Microscope (SEM)   3d view of surface - good for intact cells & viruses - uses electrons  
Scanned-probe microscopes   Doesn't modify specimen or damage it - map atomic & molecular shapes, characterize magnetic & chemical properties, & temp variation inside cells.  
Scanning tunneling microscopy (STM)   Thin metal (tungsten) probe scans specimen & produces an image revealing bumps & depressions of the atoms on surface of specimen.  
Atomic Force Microscopy (AFM)   Metal & diamond probe - 3d image - doesn't damage specimen - both biological substances & molecular processes.  
Stains are __ composed of positive & negative ion.   salts  
The color of __ dyes is in the positive ion.   basic  
The color of __ dyes is in the negative ion.   acidic  
Name some basic dyes   crystal violet, methylene blue, malachite green & safranin  
Most commonly used dyes   Basic dyes - methylene blue  
__ dyes are not attracted to most types of bacteria.   Acidic - repelled by negatively charged bacterial surface.  
Negative staining is used when for bacteria?   To prepare colorless bacteria against colored background - eosin, acid fuchsin, & nigrosin  
Simple stain   Aqueous or alcohol solution of single basic dye.  
Mordant   Chemical that increases affinity of stain for biospecimen or coats it.  
Differential stains   React differently with different bacteria & used to identify - gram stain & acid-fast stain.  
Gram stain   Stain that classifies bacteria into gram-positive & gram negative.  
4 steps of gram staining   (1) basic purple dye (primary) applied, (2) dye washed off & mordant applied, (3) alcohol-acetone solution (decolorized), (4) basic red dye applied.  
Primary stain   Basic purple dye (crystal violet)  
Decolorizing agent   Alcohol/acetone solution to remove purple from some cells.  
Gram-positive   Bacteria retaining color of purple dye & iodine after decolorization.  
Gram-negative   Lose dark violet color after decolorization.  
Counterstains   Basic dye safrain that turn gram-negative bacteria pink - doesn't affect gram-positive.  
What reacts to create gram stain?   Structural differences in cell wall - gram-positive have thicker peptidoglycan cell wall, gram-negative have lipopolysaccharides in cell wall.  
Gram-___ bacteria tend to be killed by penicillins & cephaliosporins.   positive  
Acid-fast stain   Binds to bacteria with waxy material in cell walls - mycobacterium tuberculosis & leprosy.  
What diseases can be diagnosed using acid-fast stain?   Tuberculosis & leprosy  
Special stains   Used to color & isolate special parts of microorganisms & to find capsules.  
Capsule   Gelatinous covering - determines organism's virulence  
Virulence   Degree to which pathogen can cause disease.  
Endospore   Cannot be stained by ordinary methods - resistant structure formed inside same bacteria which protects it from adverse environment.  


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