Bacterial diversity of salt tolerant nitrogen fixers around the salt mines of Himachal Pradesh

Abstract

newline Fifty two salt tolerant bacteria were isolated from rhizospheric soils of four selected newlineplants viz.,Lantana camara, Murraya koenigii, Taraxacum officinale and Cynadon dactylon newlineabundantly growing around the salt mines of Himachal Pradesh, India. Forty six bacteria showed newlinenitrogenase activity in presence of 5 per cent NaCl. Out of which, seven efficient nitrogen fixing newlinebacteria i.e. SNC9, SNC10, SNT5, SNL18, SNL19, SNC28 and SNM6, exhibited nitrogenase newlineactivity of 1292.96, 694.21, 1217.41, 484.67, 842.61, 912.72 and 387.41, nmole C2H4 h-1 mg-1 newlineprotein, respectively, however, refernce strain Azospirillum brasilense could not grow at this salt newlineconcentration. These isolates were identified on the basis of morphology, biochemical and 16S newlinerRNA typing techniques and were found as Enterobacter ludwigii (SNC9), Enterobacter cloacae newline(SNC10, SNT5), Bacillus aquimaris (SNL18, SNL19) and Bacillus vietnamensis (SNM6, newlineSNC28). Various other plant growth promoting traits of these bacteria viz., phosphate newlinesolubilization, siderophores production, indole acetic acid production and proteolytic activity newlinewere studied under salt stress (5% NaCl) conditions. The antagonistic activity of SNC9, SNC10, newlineSNT5, SNL18, SNL19, SNC28 against Fusarium oxysporum (19-56 %), SNC10, SNL18, SNM6, newlineagainst Sclerotium rolfsii (21-31 %) and SNC9, SNC10, SNM6, SNT5 against Alternaria solani newline(21-89 %) was also observed.The allele mining of nhaA gene (Na+/ H+antiporter), conferring the newlinesalt tolerance behaviour on many prokaryotes, was carried out and the gene sequences were newlinecompared among them and also with lineages of China and USA. The phylogenetic tree obtained newlinefrom the mining of nhaA gene showed variation in the protein coding region of these bacteria. newlineEffect of inoculation of salt tolerant E.ludwigii (SNC9) and non salt tolerant A.brasilense (MTCC newline125) on the growth and quality of tall fescue was also studied at different concentration of salt newlineand diesel oil (0 to 5 %). E.ludwigii (SNC9) was found much more effective in increasing the newlinegrowth