Abstract: | Plasmids containing an antisense fragment of the ς32 gene were constructed and introduced into Escherichia coli cells. Downregulation of the ς32-mediated stress response was evaluated under heat shock and ethanol stress and during the production of organophosphorus hydrolase (OPH). Northern blot analyses revealed that ς32 sense mRNA was virtually undetected in antisense-producing cultures from 5 to 20 min after antisense induction. However, lower-molecular-weight bands were found, presumably due to partial degradation of ς32 mRNA. While a >10-fold increase in ς32 protein level was found under ethanol stress in the control cultures, antisense producing cultures resulted in a <3-fold increase, indicating downregulation of ς32. Correspondingly, antisense synthesis resulted in a decreased level of a ς32 regulated chaperone (GroEL) for the first 2 h after induction relative to control cultures without ς32 antisense mRNA. The total yield of OPH in the presence of ς32 antisense was, on average, 62% of the yield without antisense. However, during ς32 antisense production, a sixfold-higher specific OPH activity was observed compared to non-antisense-producing cultures. |