Detection of Plasmids in Rhizobium Japonicum

Summary

Plasmids from 20-155 megadaltons have been detected in a variety of strains of R. japonicum. No relationship between these plasmids and hydrogen uptake capability was apparent.

Recent results indicate that in various Rhizobium species, host-range, bacteriocin production, pigment production, and hydrogenase may be associated with the presence of plasmids (Brewin et al., this volume). Autotrophic hydrogen bacteria, including strains of Alcaligenes eutrophus, are able to use hydrogen gas (H₂) as an energy source. Recent observations indicate that the hydrogen uptake (hup) capability of A. eutrophus is associated with the presence of a large plasmid (Andersen et al., submitted for publication; Tait et al., this volume). The demonstration by Evans and co-workers (Hanus et al., 1979; Evans et al., this volume) that strains of Rhizobium japonicum are capable of autotrophic growth in the presence of H₂ suggested that large plasmids may also be involved in the H₂ uptake phenotype of R. japonicum. To investigate this possibility we have examined a variety of R. japonicum strains for the presence of plasmid DNA.

A variety of R. japonicum strains were examined, including 110 (hup⁺), 110/RP4 (hup⁺), 31 (hup⁻), 76 (hup⁻), 83 (hup⁻), and soy 440 (hup⁻).