Table 3.

β-Galactosidase activities of Y. pestisKIM6+ derivatives containing p1::lacZ or p2::lacZ reporter plasmid

Strainβ-Galactosidase activity of cells grown in deferrated PMH witha:β-Galactosidase ratiosa
No added iron10 μM FeCl310 μM Heminb2.5 μM Hemoglobinb−Fe/+Fe−Fe/+Hemin−Fe/ +Hemoglobin
With pHMU44 (p1::lacZ)
 KIM6+26,946 (±4,802)1,458 (±551)23,606 (±3,430)12,312 (±1,528)20.9 (±9.2)1.1 (±0.1)2.2 (±0.4)
 KIM6-2044.1+ (ΔhmuP′RSTUV-2044.1)27,544 (±3,679)962 (±150)24,798 (±3,386)19,764 (±4,009)29.1 (±4.9)1.2 (±0.1)1.6 (±0.2)
 KIM6-2030+ (fur::kan-9)27,960 (±3,444)26,300 (±3,653)NTcNT1.0 (±0.2)NTNT
With pHMU55 (p2::lacZ)
 KIM6+1,604 (±113)1,222 (±188)1,484 (±81)955 (±131)1.3 (±0.3)1.1 (±0.1)1.7 (±0.4)
 KIM6-2044.1+ (ΔhmuP′RSTUV-2044.1)911 (±155)567 (±49)1,211 (±76)596 (±43)1.6 (±0.2)0.7 (±0.1)1.5 (±0.2)
 KIM6-2030+ (fur::kan-9)1,098 (±161)828 (±73)NTNT1.3 (±0.3)NTNT
  • a Cells were grown approximately six generations in deferrated PMH at 37°C and harvested during mid-log-phase growth. β-Galactosidase activity is expressed in Miller units (35), and the values represent an average of individual reactions from whole-cell lysates. Mean β-galactosidase ratios were obtained from averaged β-galactosidase activities from three or four experiments. Standard deviations are shown in parentheses.

  • b Desferrioxamine mesylate (Desferal) was added to a final concentration of 20 μM to chelate any contaminating inorganic iron in the hemin and hemoglobin solutions.

  • c NT, not tested.