BMSC 210 - Lecture 3

tasnimjaisee's version from 2017-09-13 17:24


Question Answer
Why is staining important?contrasts between different cells and features
ResolutionWavelength & numerical apature of lens - Shorter wave lengths = Better resolution - Max res limit 0.2μm in light microscopes
Types of light microscopyBright‐field – Phase‐contrast – Dark‐field – Fluorescence
How do compound light microscope work?Uses visible light to illuminate cells
Bright-field microscopySeen due to differences in contrast (density) of specimen & surroundings
What does Bright-field microscopy use for lenses?Objective and ocular
Equation for Bright‐field scopeTotal magnification = objective magnification = ocular magnification; max magnification use ~2000x
Phase‐Contrast MicroscopyPhase ring ↑ differences in cell and surroundings refractive index - Contrast without stain - Live samples - Dark cells on light background
↑ Numerical apertureBetter resolution & higher magnification
↓ Short wavelengths = ?Better resolution
Dark‐Field MicroscopyLight in specimen from the sides - Light scattered by specimen - Lighted cells on dark background - Observe mobility
Fluorescence MicroscopySpecimens that fluoresce, – Cells fluoresce naturally or stained - For microbial ecology enumerating bacteria in natural samples
Types of 3D MicroscopyDIC, AFM, CSLM
Differential Interference Contrast (DIC) MicroscopyPolarizer creates 2 polarized light beams - 3D - Used if bright‐field microscopy fails
Atomic Force (AFM) MicroscopyStylus measures weak repulsive forces between it & specimen and coputer generates image based on data
Confocal Scanning Laser (CSLM) MicroscopyUses laser to generate 3d image - Each layer is focused on - Resolution is 0.1μm
Electron Microscopy uses ___ instead of ___.Electrons - Photons
Types of electron microscopesTransmission electron (TEM) microscopes and Scanning electron (SEM) microscopes
Transmission Electron (TEM) MicroscopyElectromagnets are lenses - High vacuum - High mag & red 0.2nm - Samples at molecular level - Thin and stained organisms
Scanning Electron (SEM) MicroscopySpecimen coated with heavy metal thin film - Electron beam scans - Detector collects scattered electrons and image is produced - large specimens can be observed - Magnification 15x–100,000x
Major cell morphologiesCoccus/cocci - Rod - Spirillum
Coccus (pl. cocci)spherical or ovoid
Rodcylindrical shape
Spirillumbent rod shape
Cells with unusual shapesSpirochetes (long wavy) , appendaged bacteria (pump) , and filamentous bacteria
What does morphology typically does not predict of prokaryotic cell?Physiology - Ecology - Phylogeny
Morphology is important for?Nutrition uptake (Small cells with high surfave-volume ratio) - Viscus motility (helical/spiral cells) - Gliding motility (filamentous)