Osmoadaptation and plant growth promotion by salt tolerant bacteria under salt stress

Establishment of biofilm, production of exopolysacharides (EPS) and accumulation of endogenous osmolytes under varying stress conditions are significant strategies adopted by bacterial strains for their successful survival in plant rhizosphere. Our studies focus on determining the osmoadaptation strategies used by two native salt-tolerant strains Oceanobacillus profundus (Pmt2) and Staphylococcus saprophyticus (ST1) and their plant growth promoting abilities. The ability of these strains to be used as inoculants for Lens esculenta Var. masoor 93 under salt stress was tested in the laboratory. We found that unlike the bacterial growth, biofilm formation, exopolysaccharide production and endogenous osmolyte (proline and glycine betaine) accumulation increased at higher salt stress. Biofilm formation and endogenous osmolytes increased with increasing salt concentrations. The maximum increase in EPS accumulation was observed at maximum NaCl stress for ST1. Bacterial inoculation improved growth parameters and endogenous osmolytes accumulation of plants under salt stress compared to noninoculated control plants. The ST1 strain in this work efficiently produced biofilm and exopolysacharide and accumulated osmolytes in response to NaCl stress. It could be speculated that these strategies reverse the detrimental effects of high osmolarity in soil and helpful for improving crop under salt stress.