Involvement of the Haemophilus ducreyi gmhA Gene Product in Lipooligosaccharide Expression and Virulence

Abstract

The lipooligosaccharide (LOS) present in the outer membrane of Haemophilus ducreyi is likely a virulence factor for this sexually transmitted pathogen. An open reading frame in H. ducreyi 35000 was found to encode a predicted protein that had 87% identity with the protein product of the gmhA (isn) gene of Haemophilus influenzae. In H. influenzae type b, inactivation of the gmhA gene caused the synthesis of a significantly truncated LOS which possessed only lipid A and a single 2-keto-3-deoxyoctulosonic acid molecule (. 178:396-402, 1996). The H. ducreyi gmhA gene was able to complement a gmhA-deficient Escherichia coli strain, a result which confirmed the identity of this gene. When the gmhA gene of H. ducreyi was inactivated by insertion of a cat cartridge, the resultant H. ducreyi gmhA mutant, 35000.252, expressed a LOS that migrated much faster than wild-type LOS in sodium dodecyl sulfatepolyacrylamide gel electrophoresis. When the wild-type H. ducreyi strain and its isogenic gmhA mutant were used in the temperature-dependent rabbit model for dermal lesion production by H. ducreyi, the gmhA mutant was found to be substantially less virulent than the wild-type parent strain. The H. ducreyi gmhA gene was amplified by PCR from the H. ducreyi chromosome and cloned into the pLS88 vector. When the H. ducreyi gmhA gene was present in trans in gmhA mutant 35000.252, expression of the gmhA gene product restored the virulence of this mutant to wild-type levels. These results indicate that the gmhA gene product of H. ducreyi is essential for the expression of wild-type LOS by this pathogen.

Multiple factors interact to produce responses resembling spectrum of human disease in Campylobacter jejuni infected C57BL/6 IL-10-/- mice

“…This enzyme is essential for production of the heptose residues of the inner core of the LOS/LPS structure. In Haemophilus ducreyi , inactivation of the gmh A gene has been shown to result in a truncated LOS and to reduce the ability of the organism to produce skin lesions in rabbits [ 59 ]. In addition, the ability of Salmonella enterica to kill Caenorhabditis elegans was impaired by insertional inactivation of the gmh A gene [ 60 ].…”

Determining the prevalence, identity and possible origin of bacterial pathogens in soil

“…Isolates displayed indistinguishable virulence (pairwise comparisons using log‐rank test on survival fitted by Kaplan–Meier method, p > 0.25 for all comparisons). Only a single virulence gene, gmhA involved in LPS biosynthesis (Bauer et al ., 1998), was detected in the four P. alcalifaciens isolates (Fig. S7).…”