Bacteriology & Applied Microbiology

The green revolution ushered in a growth in the production of food crops in India. From a net importer of food grains,India became self-sufficient increasing the total production from 50 million metric tons in mid-sixties to 200 million metric tons in mid-eighties. This was possible due to higher yielding and hybrid varieties of seeds, increased input of chemical

fertilizers and insecticides or pesticides. However, the pitfalls of high usage of chemical fertilizers were deterioration in the quality of agricultural soil. The natural microbes present in the rhizospheric soil died due to excess chemicals and the depletion of organic carbon content. The water retention capacity was also adversely affected due to lower porosity of the soil, sometimes

the soil became acidic causing lower productivity of plants. To overcome all these problems, the use of organic manure and bio-fertilizers were introduced. These are beneficial to the crop plants due to the following properties like nitrogen fixation, inorganic phosphate solubilization, production of siderophore and production of ACC deaminase. Nitrogen fixation by symbiotic microorganisms like Rhizobium, occurring in the root nodules of leguminous plants have been reported long back. In our studies, aseptic root nodules of Fenugreek (Methi) were crushed to isolate a variety of nitrogen fixing microbes. Though microbiological and biochemical studies indicated these mucoid colonies all Gram negative with different morphologies to the

Rhizobium species, sequencing of 16s rRNA genes and molecular phylogeny showed three of the isolates (1) R1 Enterobacter cloacae (KX687556) (2) R10 Pantoea dispersa (KX687557) and (3) R12 Enterobacter ludwigii (KX687554). The temperature and salinity tolerance of these cultures were studied to increase these properties of abiotic stress tolerance. UV mutagenesis

was tried, varying the time of exposure of the plated cultures to UV radiation, the survivors (>1% of initial population) were screened for growth at 0.5 M NaCl and at 44 °C. The selected mutants of R1, R10 and R12 were studied for the plant growth promoting activities like IAA (growth hormone) production, siderophore production and phosphate solubilization. Finally, the effects of the isolated bacteria and mutants of each and a consortium of all three were pre-treated with methi seeds and germinated in pots to find out their effects on the growth of the plants. These are being analyzed after 40 days of growth in the

soil.