BIOL240L Study Guide - Final Guide: Antiseptic, Protoplasm, Resazurin

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In positive staining procedures for light microscopy, the stain is basic, and has a positively charged chromophore. Bacteria have a slightly negative outer surface and will be attracted to the stain. The methylene blue stain has a chromophore composed of: Always focus with the coarse adjustment knob, then the fine adjustment knob. The lab microscopes are parafocal they will remain in focus when changing lenses. Do not return to 40x objective with a slide that has oil on it. Other kinds of bacteria are sometimes observed including stalked forms (caulobacter), club shaped (corynebacterium) and comma shaped (vibrio). Actual size of the image (width x length in m) Bacillus subtilis: 0. 5 - 2. 5 x 1. 2 - 10. 0 m. The gram stain is used to differentiate types of bacteria. The steps in gram staining are as follows: stain the fixed smear with a primary stain of crystal violet, apply the gram"s iodine stain.