Strep-tagged LcrVs and their LCR phenotypes in Yersinia pestis. (A) Y. pestis KLD29 (ΔlcrV) expressing Strep-tagged LcrV (plcrVS1, plcrVS20, plcrVS55, plcrVS170, plcrVS228, plcrVS270, and plcrVS324) was cultured at 37°C in TMH medium supplemented with either 0 mM or 6.25 mM CaCl2. Growth was recorded as an increase in the OD600. (B) Y. pestis strain KIM D27 (wild-type lcrV) expressing Strep-tagged LcrV (plcrVS1, plcrVS20, plcrVS55, plcrVS170, plcrVS228, plcrVS270, and plcrVS324) was cultured at 37°C in TMH medium supplemented with either 0 mM or 6.25 mM CaCl2. Growth was recorded as an increase in the OD600.