BIO153H5 Chapter Notes - Chapter 27-31: Hans Christian Gram, Picrophilus, Crystal Violet
Document Summary
Compensate for water loss via osmosis by pumping k+ ions into the cell until equilibrium is reached with environment: picrophilus oshimae can grow at a ph of 0. 03, deinococcus radiodruans can survive 3 rads of radiation. Dna is shattered by radiation, ability to piece it back together using a recombination mechanism: prokaryotic cell walls. Maintain shape, protects cell, prevents from bursting in hypotonic environment. Hypertonic - most prokaryotic cells shrink away from cell walls (plasmolyze) - can inhibit reproduction: most bacterial cell walls contain peptidoglycan. A polymer composed of modi ed sugars cross-linked by short polypeptides. Enclosed the entire bacterium and anchors other molecules that extend from its surface. Archaeal cell walls lack peptidoglycan: gram staining. Samples stained with crystal violet dye and iodine then rinsed with alcohol then stained with a red dye. Structure and composition of the wall determines staining colour. Lack peptidoglycan (or thin layer) = pink = gram-negative.
