Expression of a plasmid-borne pstS::gusA gene fusion in S. meliloti strains carrying pstC1021 or pstC wild-type alleles following growth in minimal medium with limiting and excess Pi

Strain (properties)β-Glucuronidase activity (Miller units)a
P0 mediumP2 medium
RCR2011 (empty vector)40 ± 1641 ± 22
RCR2011 (pstC+, pTH1736)1,286 ± 5969 ± 21
Rm1021 (pstC1021, pTH1736)1,000 ± 641,076 ± 83
RmP110 (Rm1021, pstC+, pTH1736)1,208 ± 7073 ± 28
RmH615 (Rm1021, phoB, pTH1736)53 ± 30118 ± 16
  • a The pstS::gusA fusion plasmid was pTH1736. The β-glucuronidase activity of S. meliloti cells grown in phosphate-free MOPS minimal medium (P0 medium) or MOPS minimal medium containing 2 mM phosphate (P2 medium) was measured as described in Materials and Methods. RCR2011 carrying the empty reporter plasmid pTH1582 was used as a background control. The data are averages ± standard errors for triplicate determinations.