P-325 - Enhancing Plant Salt Tolerance through Halophyte-derived Kushineria strains: Modulation of Rhizosphere Microbial Communities and Biofilm Formation

Salt-tolerant bacteria associated with halophytic plants have evolved mechanisms to withstand extreme salinity, often benefiting plant hosts. In this study, we identified two highly halotolerant Kushneria isolates, K. konosiri (Kk) and K. marisflavi (Km), from the halophyte Suaeda maritima. These strains, capable of tolerating NaCl concentrations up to 25%, significantly enhanced Arabidopsis thaliana growth under salt stress by promoting phytohormone (notably indole-3-acetic acid, IAA) and proline biosynthesis, as well as producing exopolysaccharides (EPS) that mitigate osmotic stress. Both strains also reduced sodium ion accumulation and reactive oxygen species (ROS) levels in plant tissues, enhancing antioxidant defenses.

In a soil pot experiment, cabbage plants inoculated with both strains together (Kkm) exhibited greater growth and salt stress resistance than individual inoculations. Microbial profiling revealed a significant enrichment of Bacillus species in the cabbage rhizosphere under Kkm treatment. In vitro, Kkm more effectively stimulated Bacillus subtilis biofilm formation than either strain alone. These findings highlight Kushneria isolates as promising salt-tolerant plant growth-promoting bacteria (ST-PGPB) that restructure rhizosphere microbial communities, particularly by enhancing Bacillus biofilm formation. This study provides a foundation for developing microbial consortia to enhance plant salt tolerance with agricultural applications.