EC Microbiology

From the middle of 1950 two strains of gram-negative bacteria E. coli K-12 and the E. coli C have been extensively used in developing Molecular Genetics. These two bacteria have a single chromosome (DNA bio-macromolecule of length 4736 Kb) in CCC form (Form I) but need to be converted into its replicative form (Form II) to study DNA replication. Significantly the DNA sequences of these two strains don’t differ except the presence of xylitol operon in E. coli C. The xylitol operon changes the shape of E. coli C, size and also sensitivity to the bacteriophage phiX174. Dr Arthur Kornberg used this phage genome of length 5.3 Kb but without the knowledge of adhesion zone. This adhesion zone is the site where two membranes and cell wall of E. coli C are fused together. Before the entry into the adhesion zone of E. coli C, the phage phiX174 sends bio-signal via spike to get into the adhesion zone. After the entry into the adhesion zone the phage genome in CCC DNA (Form I) is converted into its replicative form (Form II), then multiplies and before maturation the Form II becomes Form I then encapsulation. Mature phage particles are released by rupturing the bacterial cell wall.

 Keyword: Bacteriophage phiX174; E. coli C and E. coli K-12; Adhesion Zone

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