SUMMARY: Segments of the chromosome, which included the nitrogen fixation () genes, were maintained as covalently closed circular molecules of DNA in hybrids, C-M9 and C-L4. The R factor, R , which had been used to confer fertility on the donor, was also detected as covalently closed circular DNA of molecular weight (65·4) × 10 daltons according to sedimentation studies and electron microscopy.

The genes in hybrid C-M9 were linked to on a plasmid which had a molecular weight of 9.5 X 10 daltons. A third plasmid in this hybrid had a molecular weight of 118 X 10 daltons. The Nif plasmid in C-M9 was transferred efficiently to other strains only when R was present in the donor in addition to R

Presence of three electrophoretically distinguishable gluconate-6-phosphate dehydrogenases was evidence for duplication of determinants in C-M9. Resistance of both hybrids to the rough-specific phage × 174 suggested that they inherited Klebsiella -linked genes.

Four plasmids were isolated from hybrid C-L4, one of which was R 3. Two plasmids, one carrying and and another G, were mobilized by R 3. The molecular weights of the C-L4 plasmids, excluding R , were (105 ± 1) x 10, 46 X 10 and 12 X 10 daltons.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error