Differential Proteomics in Response to Low Temperature Diazotrophy of Himalayan Psychrophilic Nitrogen Fixing Pseudomonas migulae S10724 Strain

Himalayas are considered as a reservoir of diversified and dynamic gene pool. This study describes the response of a Himalayan psychrophilic diazotroph to low temperature diazotrophy. Seven cold adaptive N₂ fixing bacteria were isolated and identified as Bacillus sp., Arthrobacter sp., Rhodococcus sp., Pseudomonas sp., etc. In order to examine the physiological response to low temperature diazotrophy, differential proteomic analysis of Pseudomonas migulae S10724 strain was carried out using two dimensional electrophoresis and MALDI–TOF–MS. Functional assessment of 66 differentially expressed proteins revealed several mechanisms thought to be involved in low temperature adaptation and nitrogen fixation, including general stress adaptation, protein and nucleic acid synthesis, energy metabolism, cell growth/maintenance, etc. Major fraction of the upregulated proteins was stress proteins, while majority of the downregulated proteins were related to cell division. Furthermore, MALDI–TOF–MS-based identification of randomly selected peptides encountered two exclusively expressed proteins: NifU family SUF system FeS assembly protein and membrane protein, suppressor for copper-sensitivity B precursor which might have a crucial role at low temperature nitrogen fixation. To the best of our knowledge, this is the first report of the isolation and differential proteomic analysis of psychrophilic diazotroph from Himalayan high altitude rhizospheric soil.