D-088. Porin-Deficient Phenotype of Haemophilus ducreyi 35000HP::P2AB

J. Davie, A. Campagnari;
Univ. at Buffalo, Buffalo, NY.

Haemophilus ducreyi is the causative agent of the sexually transmitted, genital ulcerative disease chancroid. Chancroid infection is uncommon in the United States but has been identified as a cofactor in the transmission of HIV in developing nations where both diseases are endemic. As with all gram-negative bacteria, the outer membrane (OM) is the primary permeability barrier for H. ducreyi. Porin proteins are important components of the OM, comprising a significant portion of the protein content of the OM and function as the primary means for hydrophilic solutes, wastes and antimicrobial agents to cross the OM. The loss of these critical proteins is often lethal or significantly impairs growth. H. ducreyi 35000HP expresses two porin proteins of unknown function, OmpP2A and OmpP2B. These porins are hypothesized to play a critical role in the organisms biology. However, the porin-deficient, double mutant strain 35000HP::P2AB does not exhibit a growth defect when cultured under standard media conditions. In order to identify a porin-deficient phenotype and a putative function for these porins, antibiotic and detergent sensitivity assays, real-time PCR and proteomic analysis were employed. Strain 35000HP::P2AB demonstrated statistically significant differences in sensitivity to both detergents and antibiotics relative to 35000HP. Likewise, the loss of these two porins resulted in the differential expression of 18 proteins, including the chaperone protein SecB, the proline symporter PutP, and the LPS/LOS export protein Imp. The results of these assays indicate that the loss of the porin proteins results in a decrease in membrane stability and permeability, elicits a generalized stress response in 35000HP::P2AB. Additionally, these data suggest the possibility that OmpP2A and OmpP2B may involved in H. ducreyi osmoregulation in the human host.