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Transfer of nif Genes from Klebsiella pneumoniae to other organisms
P.Deepa Sankar, C.R. Ananda Kumar, S.Lakshmi Narayanan, C. Sudha, A.J. Deepalakshmi, A. Sreedhar and A. Yuvaraja.
Department
of Agricultural Botany,
Agricultural
College and Research Institute,
Tamilnadu
Agricultural University, Madurai-625 104.
ABSTRACT
Recently advances in the understanding of bacterial nif genes have offered the prospect of transforming nitrogen fixing ability to the plants themselves. The nif genes of K. pneumoniae have long age been transferred to E.coli converting it into a nitrogen fixer. But transferring a plant cell into a nitrogen fixer is a different problem as nif genes are prokaryotic in nature. The chloroplast has been suggested as a possible target for the transfer of nif genes.
INTRODUCTION
The introduction into crops the ability to fix nitrogen from the atmosphere would not only save on the cost of applying nitrogenous fertilizers, but would eliminate the potential problems of water pollution from nitrates washed off from agricultural land (Ignacimuthu 1995). Achievement of associations between nitrogen fixing bacteria and cereals would have important agricultural applications. Research is going on to develop new nitrogen fixing systems by means of somatic hybrids between the desired cultivars and nitrogen fixing plants; or by introducing nif genes into symbiotic or free living microorganisms, also to transfer the nitrogen-fixing ability to plants by using viruses or self transmissible plasmids as vectors of the nif genes; or by recombining these genes with mitochondrial or chloroplastic DNA.
NITROGEN FIXING PROKARYOTE Klebsiella pneumoniae
Klebsiella pneumoniae is a gram negative bacterium. It forms the model system for nif genetics. It is a free living bacterium and is a facultative aerobe. It fixes nitrogen when they grow anaerobically. The nif genes of K. pneumoniae are clustered on the chromosomal DNA. There are 17 nif genes which occupy 33 kilobases of DNA in the nif gene cluster. In K. pneumoniae nif gene regulation involves local control by genes within the nif gene complex and more global control by regulatory genes located elsewhere in the genome.
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