ALTERATIONS IN LEVELS OF DNAK AND GROEL RESULT IN DIMINISHED SURVIVALAND ADHERENCE OF STRESSED HAEMOPHILUS-DUCREYI

Haemophilus ducreyi is a hemin-requiring bacterium causing the genital ulcer disease chancroid. Previously we demonstrated that the heat sho ck protein GroEL was immunogenic and possibly highly expressed in a ma mmalian host. The present study was initiated to (i) determine the rel ative amounts of GroEL expressed by H. ducreyi during in vitro exposur e to stresses and (ii) evaluate whether a high level of GroEL is direc tly or indirectly required for survival and adherence of stressed H. d ucreyi. Using scanning densitometry of sodium dodecyl sulfate-polyacry lamide gel electrophoresis protein profiles, we found that H. ducreyi expressed high basal levels of GroEL, averaging fivefold greater than in Escherichia coli, These high GroEL levels increased up to twofold u pon exposure of the organism to heat shock or high levels of hydrogen peroxide and during adherence to two human genital cell lines, Further more, when the gene for DnaK was present on a multicopy plasmid in H, ducreyi, a 1.8-fold increase in DnaK and a 2.3-fold reduction in GroEL were seen. These results suggest that DnaK serves as a negative modul ator of H. ducreyi GroEL. Subsequently we found that H. ducreyi ,vith lower GroEL had diminished ability to survive when challenged by heat and oxidative stresses. In addition, the long, parallel chains charact eristic of virulent strains of H. ducreyi were absent when GroEL was l owered, so that fewer bacterial cells adhered to the human cells, Thes e results suggest that the unusually high basal levels of GroEL are in volved, either directly or indirectly, in the survival, chaining, and adherence of H. ducreyi in the presence of the combined stresses of th e host environment.