Haemophilus ducreyi Isoprenoid Quinone Content and Structure Determination

We found that Haemophilus ducreyi, the etiologic agent of chancroid, contains two isoprenoid quinone structural types, demethylmenaquinone and menaquinone, with six- and seven-unit unsaturated isoprene side chains, respectively. Eleven strains of H. ducreyi and a control strain of Haemophilus influenzae biogroup aegyptius (Haemophilus aegyptius) were grown in a liquid medium with oxygen as the terminal electron acceptor. Quinones were extracted from bacterial membrane preparations and isolated by high-performance liquid chromatography. The chemical structure of both quinone types was determined by using ultraviolet and mass spectroscopy and nuclear magnetic resonance analysis. The presence of both a demethylmenaquinone and a menaquinone in H. ducreyi represents a major physiological and chemotaxonomic difference between H. ducreyi and other Haemophilus species.