The specific uptake of cloned Haemophilus DNA.

During the process of transformation $\text{Haemophilus}\text{influenzae}$ cells bind its own DNA but little or no foreign DNA. This specificity for recognition of DNA was studied by cloning Haemophilus DNA in $\text{E. coli}$. Haemophilus DNA fragments were cloned using plasmid pBR322 as a vector. The fragment cH7 cloned in pBR322 was found to be homologous to Haemophilus DNA and shown to bind irreversibly to competent Haemophilus cells. The fact that cH7 isolated from $\text{E. coli}$ lacks Haemophilus modification leads to the conclusion that modification does not play a role in the uptake mechanism. Uptake specificity is a function of recognition sequences that reside in DNA itself.