Studies on the osmo-tolerance in terms of repressed / over expressed-protein and differential display gene expression profiling in biocontrol strains of Pseudomonas spp.
Paul, Diby; Srinivasan, Bharthkumar and Nair, Sudha (2004) Studies on the osmo-tolerance in terms of repressed / over expressed-protein and differential display gene expression profiling in biocontrol strains of Pseudomonas spp. In: 13th Southern Regional Conference on Microbial Inoculants, 3-5 Dec 2004, Bijapur, Karnataka, India.
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Salt tolerant strains of Pseudomonas were isolated from rice-rhizosphere of coastal agri-ecosystem and their biocontrol-potential was elucidated against Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, in vitro and in planta. The efficient strains were tested for their tolerance to different concentrations of NaCl and a relation was made with cell density at A-600. The strains tolerated up to 2M of NaCl in minimal medium. The present study deals with elucidation of the osmolyte-mediated and repressed/over expressed protein-mediated mechanism of osmo-tolerance in the bacterial strains. The differential-display gene-expression profiling of the osmo-regulated genes also throws light on the basic mechanism of osmo-regulation in Pseudomonas. Natural abundance 13C Nuclear Magnetic Resonance Spectroscopy and HPLC-Amino acid analyser studies revealed the accumulation / de novo synthesis of osmolytes in the cytosol of the bacteria. The PAGE protein profiling of total cell proteins revealed many induced/repressed proteins. The outer membrane (OM) and inner membrane (IM) proteins also were resolved separately in PAGE and the induced/repressed proteins need to be further characterised. Differential display gene expression profiling was carried out after isolating the total pool of m-RNAs from the normal and stressed bacteria and the radio-labelled cDNA was resolved in polyacrylamide gel which displayed an array of up-regulated and down regulated genes which is being sequenced and characterised. In another study conducted in planta, it was found that the root colonization potential of the strains were not hampered with varying salt concentrations in soils (Electrical Conductivity of 0.25 – 3.20 m mhos/cm). The osmo-tolenace mechanism of the bacteria is assumed to aid the bacteria in root colonization even in osmotic stress, which needs to be further elucidated. Understanding the mechanism of osmo-adaptation in rhizobacteria will contribute to the long-term goal of enhancing plant-microbe interaction for the improvement of crops grown in coastal agricultural niche.
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