transmission electron microscopy was used to study the cellular morphologies of a wild-type rhizobium meliloti strain ( l5-30 ) , a nitrogen fixation-ineffective ( fix- ) succinate dehydrogenase mutant ( sdh- ) strain , and a fix+ sdh+ revertant strain within alfalfa nodules and after free-living growth in a minimal medium containing 27 mm mannitol plus 20 mm succinate .
C0038615
succinate dehydrogenase
C0283592
sdh