Griffith was working with the micro-organism Diplococcus pneumonia also called Pneumococcus, a bacterium causing pneumonia. Some strains of this bacterium have a smooth polysaccharide capsule which causes disease and are designated as virulent S type strains. In a mutant strain the bacteria have no capsule, and when grown on the surface of an agar plate, they form small rough colonies [...]
In this article we will discuss about the genetic map of E.coli. Several methods have revealed that the genetic map of the main chromosome of E. coli is an un-branched circle with a circumference of 100 minutes (Fig. 17.5) which corresponds to the transfer time during conjugation. About 650 genes have been mapped. Some important features of the genetic map [...]
In this article we will discuss about the definition of conjugation in bacteria. The occurrence of recombination by sexual union was first shown experimentally in 1946 by Joshua Lederberg and E.L. Tatum in E. coli. They took two auxotrophic strains neither of which could grow on minimal medium due to mutation in genes controlling synthesis of vitamins thiamine and biotin, [...]