Table 2.

The influence of different inducible RstRs on expression of rstA-lacZ reporters

ReporteraRepressor constructaβ-Galactosidase activitybFold repressionc
No ARA0.05% ARA
rstA c,a l c-lacZ pBAD33890882NS
pBADRstRc,a l c 1,8683948
pBADRstRET 1,5631,641NS
pBADRstRc l a s s 1,2562,315NS
rstA ET-lacZ pBAD3310072NS
pBADRstRc,a l c 192133NS
pBADRstRET 1331.874
pBADRstRc l a s s 161114NS
rstA c l a s s-lacZ pBAD33398332NS
pBADRstRc,a l c 946749NS
pBADRstRET 745680NS
pBADRstRc l a s s 6168.870
  • a Reporter and repressor pairs were introduced into E. coli CC118. The rstA calc-lacZ reporter was pBD40, therstA ET-lacZ reporter was pHK102, and the rstA class-lacZ reporter was pHK101. The ARA-inducible Calcutta, El Tor, and classical RstRs were pBD87, pHK1, and pHK2, respectively.

  • b β-Galactosidase activity within overnight cultures is reported in Miller units (14).

  • c Fold repression was calculated by dividing the β-galactosidase activity in the absence of ARA by the β-galactosidase activity in the presence of ARA. Changes in β-galactosidase activity of less than twofold were deemed not significant (NS).