Identification and characterization of plasmids in hydrogen uptake positive and hydrogen uptake negative strains ofRhizobium japonicum

Abstract

Modifications were made of published procedures to allow routine isolation of plasmids fromRhizobium japonicum. The plasmid profiles of a series of H2 uptake positive and H2 uptake negative strains were compared. None of the strains ofR. japonicum with high H2 uptake activities exhibited discernible plasmids, while most of the strains, with little or no H2 uptake activity, showed plasmids with molecular weights ranging from approximately 49–290 x106. An examination of H2 uptake negative mutants derived from an H2 uptake positive parent revealed two discernible plasmid bands in nonrevertible mutants but no detectable plasmids in revertible mutants or in the parent strain from which mutants were derived.