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Overlapping sequences of Klebsiella pneumoniae nifDNA cloned and characterized
Abstract:
A HindIII (17.0 kb) and an EcoR1 restriction fragment (6.9 kb) of Klebsiella pneumoniae nif DNA were cloned on two small amplifiable plasmids, pCM1 and pSA30 respectively. These plasmids between them carry 14 of the 15 known Klebsiella nif genes. The operon for the three structural genes for nitrogenase, nifpHDK, is carried on pSA30: four and five of the remaining six operons are on pCRA37 and pCM1 respectively. All of the nif genes were assigned to endonuclease restriction fragments of DNA using the Southern blotting technique (Southern, 1975) with total DNA of nif insertion mutants and radioactive plasmid DNA which contained cloned nif DNA sequences. Their locations were consistent with the genetic map of nif genes. The estimated size of the nif gene cluster was 24 kb.
Insights
Researchers cloned Klebsiella pneumoniae nitrogen fixation (nif) genes onto plasmids, mapping 14 of 15 known nif genes. This work details the organization and size of the nif gene cluster, crucial for understanding bacterial nitrogen metabolism.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Nitrogen fixation is a vital process for plant growth, primarily carried out by bacteria possessing the nitrogen fixation (nif) genes.
- Understanding the organization and regulation of nif genes is crucial for improving nitrogen utilization in agriculture.
Purpose of the Study:
- To clone and physically map the nitrogen fixation (nif) genes of Klebsiella pneumoniae.
- To determine the organization and estimate the size of the nif gene cluster.
Main Methods:
- Cloning of HindIII and EcoR1 restriction fragments of Klebsiella pneumoniae nif DNA onto plasmids pCM1 and pSA30.
- Southern blotting technique using radioactive plasmid DNA and nif insertion mutant DNA to assign nif genes to DNA fragments.
- Restriction fragment analysis to map gene locations.
Main Results:
- Successfully cloned 14 out of 15 known Klebsiella pneumoniae nif genes on two plasmids, pCM1 and pSA30.
- The nif operons, including nifpHDK, were localized on the cloned fragments.
- The estimated total size of the nif gene cluster was determined to be 24 kb, consistent with the genetic map.
Conclusions:
- The study provides a detailed physical map of the Klebsiella pneumoniae nif gene cluster.
- The cloned nif DNA sequences and mapping data are valuable resources for further research into nitrogen fixation mechanisms.