FIG. 2.

RT-PCR expression analysis of selected RAP products. All reactions were performed under stringent conditions using specific primers (see Materials and Methods for experimental details). (A) Autoradiographs of RT-PCRs on RNAs isolated from free-living oxic bacteria (lane 1), bacteria subjected to microoxic conditions (2% O₂) (lane 2), and bacteria submitted to severe microoxic conditions (<1% O₂). Lanes 1 to 3, growth in TY rich medium; lane 4, 3-week-old bacteroids. hemA, control. (B) Expression patterns of RAP genes in nifA, fixK, and fixJ regulatory mutants of S. meliloti. RT-PCRs were performed on RNAs isolated from symbiotic bacteroids 2 weeks after inoculation of alfalfa with the wild-type strain (GMI 211) (lane 5), a fixK mutant (GMI 942) (lane 6), a nifA mutant (GMI 5601) (lane 7), and a fixJ mutant (GMI 5704) (lane 8).