Plasmid visualization and nif gene location in nitrogen-fixing Azospirillum strains

Abstract

A modified gel electrophoresis technique provided a reproducible way of detecting and isolating plasmids with molecular weights ranging from 12 x 106 to 370 x 106 for Azospirillum species. Analysis with the nifHD region of Rhizobium trifolii showed that the Azospirillum nif genes were chromosomally located in all eight strains investigated and not on endogenous plasmids.