Table 2.

β-galactosidase and alkaline phosphatase activities ofY. pestis KIM6+ and KIM6 derivatives grown to mid-log phase in defined PMH medium

StrainAlkaline phosphatase or β-galactosidase activitya of cells grown in medium with:Induction ratiob
10 μM FeCl3 (37°C)1.0 μM FeCl3 (37°C)1.0 μM MnCl2 (37°C)No added FeCl3 or MnCl2−Fe/+10 μM Fe−Fe/+1.0 μM Fe−Fe/+Mn26°C/37°C
37°C26°C
PhoA strains
 KIM6(pYFE34)+c 2293695761,5325.1 (1.6)4.7 (1.4)2.6 (0.2)
 KIM6(pYFE34)3264366472,0713,2957.2 (2.4)5.7 (0.9)3.5 (0.2)1.8 (0.3)
 KIM6(pYFE47)2393175371,3065.4 (1.4)4.8 (2.1)2.4 (0.3)
 KIM6-2030(pYFE47)1,8301,8651,9402,0461.2 (0.3)0.9 (0.4)0.9 (0.2)
LacZ strains
 KIM6(pEUPP1)+1966231,1021,4037.3 (2.7)2.3 (0.05)1.3 (0.04)
 KIM6(pSC27.1)+1,0601,4122,2652,6482.6 (0.6)2.2 (0.2)1.2 (0.04)
 KIM6(pSC27.1)1,7264,3072.5 (0.1)
  • a Units of phosphatase activity were calculated as 1,000 × [(OD420 − 1.75 × OD550)/time × OD620 × volume], where OD420 is optical density at 420 nm (16). β-Galactosidase activity is expressed in Miller units (55). Values are the means for samples taken from at least two independent experiments. In the absence of reporter genes, Y. pestis cells are phenotypically PhoA and β-galactosidase negative.

  • b Values in parentheses represent standard deviations.

  • c Names followed by a + are those ofY. pestis strains containing an intact 102-kb pigmentation (pgm) locus (59).