Evidence from the Cytology of Azotobacter chroococcum of a Relationship with Rhizobium and the Bacillaceae

Abstract

SUMMARY: The structure of the cell envelopes in Azotobacter chroococcum and the behaviour and mode of formation of the spore-like cysts suggest that this organism has a close phylogenetic relationship with the Bacillaceae, and that accordingly the main genera of nitrogen-fixing bacteria, Azotobacter, Rhizobium, and Clostridium, have a relatively recent common origin.