EXPLORATION OF ENDOPHYTIC AND SULFATE-REDUCING BACTERIA FROM TIDAL SWAMP SOIL AND RICE PLANTS FOR THE DEVELOPMENT OF MICROBIAL CONSORTIUM

Abstract

Tidal swamp land has significant potential for rice cultivation; however, its productivity is often constrained by anaerobic soil conditions, high acidity, and the accumulation of toxic compounds such as Fe²⁺ and sulfide. This study aims  explore and evaluate the synergistic interactions between plant growth-promoting endophytic bacteria and sulfate-reducing bacteria in improving soil fertility and rice growth in tidal swamp ecosystems. Endophytic bacteria were isolated from root, stem, and leaf tissues of rice plants, while sulfate-reducing bacteria were isolated from rhizosphere soil in both cultivated and uncultivated tidal swamp areas in Barito Kuala Regency, South Kalimantan. A total of 13 endophytic bacterial isolates and 4 sulfate-reducing bacterial isolates were successfully obtained. Isolates were characterized based on morphology, synergism tests, hypersensitivity reactions, phosphate solubilization ability, and indole-3-acetic acid (IAA) production. The synergism test results indicated that all isolates were compatible, with no inhibition zones observed. Morphological characterization showed that most isolates had circular colonies with smooth margins, convex elevation, and color variations ranging from white to yellowish, predominantly consisting of Gram-negative cocci and some rod-shaped bacteria.Potential isolates as consortium candidates included 3A END, 5A END, 2A BPF, 3A BPF, 3A BFN, as well as sulfate-reducing bacteria isolates 1 SM and 5 SM. Isolates 2A END and 5D END exhibited the highest IAA production potential, which plays an important role in stimulating root growth and enhancing nutrient uptake in plants.Analysis of soil physical and chemical properties revealed acidic conditions, with Fe content of 7548.60 ppm and S content of 801.28 ppm, both categorized as very high, which negatively affect nutrient availability