Ppt 1

resolves images of individual bacteria based on their absorption of light.

bright field, dark field, phase contrast, fluorescence

use beams of electrons to resolve details several orders of magnitude smaller than those seen under light micrscopy

SEM, TEM,

use van der waals forces between a probe and object to map the 3d topography of cell

detect interference pattern of xrays entering the crystal lattice of molecule

• 1. contrast between object and its medium
• 2. wa velength smaller than object
• 3. a detector with sufficient resolution for the given wavelength

Bacteria and Archaea

photon's energy is acquired by the absorbing object

wave front bounces off the surface of an object

bending of light as it enters a substance that slows its speed

when wave front interacts with an object smaller than wavelength of light

as they enter a substance of a higher refractive index

light rays are brought to a focal point

• 1) use shorter wavelength light
• 2. lessen contrast
• 3. use of immersion oil
• 4. use of wider lens closer to specimen

phase - contrast microscopy

phase-contrast microscopy

phase contrast microscopy

incident light is absorbed by the specimen and re-emitted at a lower energy, thus longer wavelength

• both excitation light and emitted lights are focused together.
• -visualize cells in 3d
• -allows observation of live microbes in real time

Electrons pass thru the specimen and reveals internal structures

Electrons scan the specimen surface and reveals external features in 3D

cuts slices thru specimen in EM

• aka cryo-electron microscopy (cryo-EM)
• specimen is flash-frozen (suspended in water and frozen rapidly

• avoids need to physically slice sample for thin section TEM
• -generate high resolution model of cirus particles

measures the van der Waals forces between electron shells of adjacent atoms of the cell surface and the sharp tip

Scanning probe microscopes; enable nanoscale observation of cell surfaces, including living cells suspended in water