Effect of High Temperature on Pseudomonas putida NBRI0987 Biofilm Formation and Expression of Stress Sigma Factor RpoS
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Pseudomonas is an efficient plant growth–promoting rhizobacteria; however, among the limiting factors for its commercialization, tolerance for high temperature is the most critical one. After screening 2,500 Pseudomnas sp. strains, a high temperature tolerant–strain Pseudomonas putida NBRI0987 was isolated from the drought-exposed rhizosphere of chickpea (Cicer arietinum L. cv. Radhey), which was grown under rain-fed conditions. P. putida NBRI0987 tolerated a temperature of 40°C for ≤ 5 days. To the best of our knowledge, this is the first report of a Pseudomnas sp. demonstrating survival estimated by counting viable cells under such a high temperature. P. putida NBRI0987 colony-forming unit (CFU)/ml on day 10 in both the absence and presence of MgSO4.7H2O (MgSO4) in combination with glycerol at 40°C were 0.0 and 1.7 × 1011, respectively. MgSO4 plus glycerol also enhanced the ability of P. putida NBRI0987 to tolerate high temperatures by inducing its ability to form biofilm. However, production of alginate was not critical for biofilm formation. The present study demonstrates overexpression of stress sigma factor σ S (RpoS) when P. putida NBRI0987 is grown under high-temperature stress at 40°C compared with 30°C. We present evidence, albeit indirect, that the adaptation of P. putida NBRI0987 to high temperatures is a complex multilevel regulatory process in which many different genes can be involved.
KeywordsAlginate Nutrient Broth Crystal Violet Cicer Arietinum Alginate Production
Thanks are due to the director of the National Botanical Research Institute, Lucknow, for necessary support of this study. The study was supported by Task Force Grant No. SMM-002 from the Council of Scientific and Industrial Research, New Delhi, India, awarded to C. S. N.
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