A 30 kb DNA region from Sp7, containing the nitrogenase structural genes (), has been cloned. The presence of genes, in the 20 kb located next to , was explored by Tn5 mutagenesis after subcloning various restriction fragments in the broad-host-range suicide vehicle pSUP202. Over 25 mutations due to Tn5 random insertions were obtained in the 20 kb and each recombined into the genome of strain Sp7. Four new loci were identified, located at about 4, 9, 12 and 18 kb downstream from respectively. Hybridization with heterologous probes from and was performed to characterize the new regions. The region proximal to appears to contain and the region distal to contains genes homologous to and gene(s) from the fourth locus were not identified. Mutants in this locus, which were devoid of nitrogenase activity when tested under nitrogen-free conditions, displayed a high nitrogenase activity when glutamate was added to the growth medium. This phenomenon was also observed with mutants of the homology region, but to a lesser extent. Homology between strain Sp7 total DNA and a -containing probe from was detected, although the hybridizing region was not part of the cluster described above.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

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