The role of disulfide bond isomerase A (DsbA) of Escherichia coli O157 : H7 in biofilm formation and virulence

The role of periplasmic disulfide oxidoreductase DsbA in Shiga toxin-producing Escherichia coli O157:H7 (STEC) was investigated. Deletion of dsbA (Delta dsbA) significantly decreased cell motility and alkaline phosphatase activity in STEC. STEC Delta dsbA also showed greater sensitivity to menadione and under low pH conditions. Significant reductions in surface attachment to both biotic (HT-29 epithelial cells) and abiotic (polystyrene and polyvinyl chloride) surfaces were observed in STEC Delta dsbA. In addition, no biofilm formation was detected in STEC Delta dsbA compared to wild-type cells in glass capillary tubes under continuous flow-culture system conditions. In the nematode model Caenorhabditis elegans-killing assay, the deletion of dsbA in STEC resulted in attenuated virulence compared to wild-type cells. STEC Delta dsbA was also found to have a reduced ability to colonize the nematode gut. These results suggest that DsbA plays important roles in biofilm formation and virulence in STEC cells.