Unveiling the Role of Metabolites from a Bacterial Endophyte in Mitigating Soil Salinity and Reducing Oxidative Stress.

Several plant-associated microbes have the capability of ameliorating the adverse effects of salinity stress in plants. Such microbes produce metabolites, including proline, glycine betaine, and secondary compounds, like melatonin, traumatic acid, and β-estradiol, which have been found to have a role in reducing salinity-induced damage in plant cells. While the effects of these metabolites have been studied, their application-related aspects remain underexplored. In this study, we investigated the salinity-stress-alleviating potential of metabolites derived from the endophytic bacterium Bacillus safensis BTL5. The microbial metabolites were extracted using the hexane-chloroform fraction method and identified through LC-HRMS analysis. Four metabolites (traumatic acid, β-estradiol, arbutin, and α-mangostin), along with a fifth compound, melatonin, were initially screened for their salinity alleviation potential. Subsequently, two metabolites, i.e., arbutin and β-estradiol, were evaluated for their impact on growth parameters and enzymatic antioxidant activities under 200 mM salt stress. The results revealed that arbutin and β-estradiol significantly improved plant growth, chlorophyll content, and enzymatic activities while reducing oxidative damage. The dose-dependent effects highlighted optimal concentrations for maximum efficacy from these compounds under elevated salinity. This study signifies the potential of microbial metabolites in enhancing crop resilience to salinity, highlighting their role in sustainable agriculture. The outcomes of this study provide a baseline for the applied use of such microbial metabolites under field conditions.