Isolation and characterisation of Haemophilus influenzae type b mutants defective in transferrin-binding and iron assimilation.

The quinone antibiotic streptonigrin was used to select mutants of Haemophilus influenzae type b defective in human transferrin binding. Compared with the parent wild-type strain (JKP1), mutant JKP5 was unable to bind transferrin whilst mutant JKP4 showed reduced binding. JKP5 appeared to lack an approximately 72 kDa transferrin-binding protein. Unlike JKP1, neither JKP4 nor JKP5 were able to acquire iron from human transferrin but their ability to use a variety of other iron and haem compounds as iron sources was unaffected. Such mutants should prove useful in further elucidating the mechanism of transferrin iron-acquisition and its contribution to the virulence of H. influenzae.