Host Specificity of DNA in Haemophilus influenzae: The Restriction and Modification Systems in Strains Rb and Rf

Abstract

Summary: Haemophilus influenzae Rf possesses two distinct host specificity systems F1 and F2 each of which is able to restrict and modify Haemophilus phage HP1c1, while strain Rb possesses only one system, B. Among restriction-deficient mutants isolated from strain Rf , the r - m + as well as r - m - phenotypes for these two systems were obtained after either one or two mutational steps. The F1 system was introduced into H. influenzae Rd by genetic transformation to show that the D1 and F1 systems are not allelic.