Bacterial Cell wall and Gram Staining

Bacteria can be divided into two large groups on the basis of differential staining technique called Gram Stain developed by Christian Gram.

      Gram Staining  Procedure

Gram Staining Procedure

Gram Positive Bacteria
  • Split into a low and high GC group which reflects the GC content of their DNA.
  ex: Staphylococcus, Actinobacteria, Streptococcus, Lactobacillus, Cornyebacterium, Listeria ,Bacillus, Nocardia, Clostridium
Gram negative bacteria
  •   Proteobacteria is the largest and diverse group of bacteria including many of the more commonly known gram-negative bacteria.
  • Carl Woese (1987) established this grouping, calling it informally the "purple bacteria and their relatives".The group is defined primarily in terms of  rRNA sequences. The Proteobacteria are divided into six sections, referred to by the Greek letters alpha through zeta, again based on rRNA sequences.
 Ex: Escherichia coli (E.coli),Helicobcater, Salmonella,Cyanobacteria, Klebsiella,Hemophilus, Neisseria, Pseudomona
A comparison of cell walls of Gram positive and Gram negative bacteria


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  1. The Q and As are very useful, but why not allow students/viewers to print out as a record for future revision ? Thanks PL

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