BIOMI 2900 Lecture Notes - Lecture 2: Scanning Electron Microscope, Gram Staining, Reynolds Number

• School: Cornell University
• Department: Microbiology
• Course: BIOMI 2900
• Professor: Daniel Buckley

Document Summary

Staining motility: increases contrast but need to kill sample (so no, simple = stain indiscriminately, compound stain = differentiate structure (different types of cells are stained different colours); e. g. gram stain (cid:1) (cid:1) (cid:1) (cid:1) Depends on the refraction index: cells have a slightly different refractive index than. Exploit refractive index in order for cells to appear darker water and air against a lighter background: allows for the viewing of organelles. No need for stain so cells are normally alive (can observe motility) Background will be black and sample glows a bit. Light comes from the back, hits a mirror, and then hits the sample. Light excites the sample (esp. if there"s fluorescent cells) View light given off by the sample. Can stain sample to make it fluorescent (cid:1) Electron vibrate at smaller scale than light so can views much smaller samples. Coat specimens with metal and then bounce electrons off.