nifH homologs from soil metagenome

Abstract

Biological nitrogen fixation is an important process that allows nitrogen uptake into biological systems. But it is still unclear from where the first nif gene was formed or evolved. Soil samples from different agro-climatic zones of western Indian Himalaya were analysed for the diversity of nifH in their metagenome. Metagenomic DNA was isolated followed by polymerase chain reaction (PCR) amplification and quantification. Soil of Pithoragarh (locality of temperate climatic region) was further used for shotgun meta-genomic library construction. Clones having similar insert were screened and finally 176 clones were used for colony hybridisation. All the clones were hybridised with two nifH probes, i. e. NB6 and BR1 and positive clones were sequenced. In-silico study of sequenced shotgun clones reveals nifH homology with several other genes which are not directly involved in nitrogen fixation but belong to bacterial genera which are known for nitrogen fixing ability. We are proposing a hypothesis that nif genes like nifH may evolve from their nearest genes or adjacent regions and in due course become specific in their functions.