The nitrogen fixing rhizobia have different nod and nif genes but where is their location? Are the genes located in plasmids or in the chromosome of the bacteria?
In some rhizobia, the nif genes are located on plasmids called 'sym plasmids' (sym = symbiosis) which contain genes related to nitrogen fixation and metabolism, while the chromosomes contain most of the housekeeping genes of the bacteria. A majority of the nif genes are plasmid borne in the rhizobia, but are located on chromosome in the. Bradyrhizobium.The nif genes have structural and functional-relatedness to the N fixation genes found in Klebsiella pneumonia. The structural nif genes from taxonomically diverse microbes are nearly identical and function in a similar manner to encode nitrogenase . A majority of the nif genes are plasmid borne in the rhizobia, but are located on chromosome in the Bradyrhizobium. Nitrogen fixation in symbionts and free-living microbes is catalyzed by nitrogenase, an enzyme complex encoded nifDK and nifH genes.
Nice response form Dr Prem Baboo...
Rhizobium nod genes, and their product, Nod Factor (NF), have
been recognized as essential for the development of nitrogen-fixing nodules on legume roots . Mutations within or deletions of entire nod genes result in a loss of the ability of rhizobial bacteria to induce nodules on the host, and therefore fix atmospheric nitrogen. There are other different genes involved in symbiotic nitrogen fixation in addition to nod, nif and fix genes.The nif genes have structural and functional-relatedness to the N fixation genes found in 2 Klebsiella pneumonia. The structural nif genes from taxonomically diverse microbes are nearly identical and function in a similar manner to encode nitrogenase . A majority of the nif genes are plasmid borne in the rhizobia, but are located on chromosome in the Bradyrhizobium. Nitrogen fixation in symbionts and free-living microbes is catalyzed by nitrogenase, an enzyme complex encoded nifDK and nifH genes. Nitrogenase itself consists of a molybdenum-iron protein (MoFe), subunit I and an iron-containing protein (Fe) subunit II. The MoFe Protein subunits are encoded by nifK and nifD and a FeMo cofactor (FeMo-Coo) is required for activation Mo-Fe protein.Some PDFs enclosed for further reading...
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