Plasmid transfer within and between serologically distinct strains of Rhizobium japonicum, using antibiotic resistance mutants and auxotrophs

Area of Science:

• Microbiology
• Bacteriology
• Genetics

Background:

• Rhizobium japonicum is a crucial nitrogen-fixing bacterium.
• Understanding plasmid transfer in Rhizobium is vital for genetic manipulation and agricultural applications.
• Auxotrophic and antibiotic-resistant mutants are essential tools for genetic studies.

Purpose of the Study:

• To isolate auxotrophic and antibiotic-resistant mutants of Rhizobium japonicum.
• To investigate the transferability of P-1 group plasmids (R68.45 and RP4) within and between specific R. japonicum strains.
• To determine the success rate of plasmid transfer to different R. japonicum strains, including USDA 138.

Main Methods:

• Isolation of methionine-requiring and pantothenic acid-requiring auxotrophs from R. japonicum USDA 31.
• Generation of highly antibiotic-resistant mutants from R. japonicum strains USDA 31, USDA 110, USDA 138, and Webster 48.
• Conjugation experiments to transfer plasmids R68.45 and RP4 using the isolated mutants.

Main Results:

• Successful isolation of auxotrophic and antibiotic-resistant mutants.
• Efficient transfer of plasmids R68.45 and RP4 was achieved within and between R. japonicum strains USDA 31, USDA 110, and Webster 48.
• Plasmid transfer to R. japonicum strain USDA 138 was unsuccessful under the tested conditions.

Conclusions:

• The developed mutants are suitable for plasmid transfer studies in Rhizobium japonicum.
• Plasmid transfer efficiency varies significantly between different R. japonicum strains.
• Strain USDA 138 exhibits resistance or a barrier to the tested plasmid conjugations.