A regulatory circuit composed of three porins (OmpF, OmpC, and OmpX) and two transcriptional regulators (OmpR and CRP) has previously been characterized in Yersinia pestis . In this follow-up study, OmpF2, an OmpF paralogue, was integrated into this regulatory circuit. Only basal expression was detected for ompF2 in the wild-type strain under different osmotic conditions. The ompF2 transcription was dramatically enhanced with increasing medium osmolarity in the ompR null mutant background. The CRP regulator had no regulatory effect on ompF2 under the growth conditions tested.