Danish Physician Hans Christian Gram Stain, Escherichia...

Gram Staining: Micrococcus leteus, Escherichia coli, and Unknown Colony Ethan Hinkle Microbiology Lab 3051, Section 001 Instructor: Harrison Taylor February 9, 2015 This report represents my individual effort. I did not receive or offer aid to anyone when performing this assignment, nor did I plagiarize any material. Signed: __________________________________________________________ INTRODUCTION In 1884, Danish Physician Hans Christian Gram was in the process of developing a staining procedure that would potentially differentiate prokaryotic (mainly bacterial cells) and eukaryotic nuclei in tissue samples. However, Gram was not effective in developing the differential tissue stain, his derived work would serve as the most valuable differential stain in bacteriology, the Gram-stain (1). Moreover, it soon became clear that most bacteria could be catorgorized into two major groups based upon their response to the Gram-staining procedure. Gram-positive bacteria stained purple, whereas Gram-negative bacteria stained a pink-red (2). Complete structures of Gram-positive and Gram-negative cells were not differentiable until the development of the transmission electron microscope. Gram-positive bacteria comprise of a singular, 20-80nm thick homogenous layer of peptidoglycan just outside the plasma membrane. In comparison, Gram-negative have two apparent layers: a 2-7nm thick peptidoglycan layer incased in a 7-8nm thick outer membrane. The most distinct