Restoration of the soil fertility under Cr(VI) and artificial drought condition by the utilization of plant growth–promoting Bacillus spp. SSAU2

Abstract

The study explores the potential of an indigenous halo-tolerant microbe identi ed as Bacillus spp. SSAU-2 in enhancing soil fertility and promoting plant growth for sustainable agricultural practices under the in uence of multiple abiotic stresses such as Cr (VI), high salinity and arti cial drought condition. The study investigated various factors in uencing IAA synthesis by SSAU-2, such as pH (5 to 11), salinity (10 g/L to 50 g/L), tryptophan concentration (0.5 to 1%), carbon (Manitol and Lactose), and nitrogen sources (Peptone and Tryptone). The highest IAA concentration was observed at pH 10 (1.695 mg/ml) and pH 11 (0.782 mg/ml). IAA synthesis was optimized at a salinity level of 30g/l, with lower and higher salinity levels resulting in decreased IAA concentrations. Notably, the presence of mannitol and lactose signi cantly augmented IAA synthesis, while glucose and sucrose had inhibitory effects. Furthermore, peptone and tryptone played a pivotal role in enhancing IAA synthesis, while ammonium chloride exerted an inhibitory in uence. SSAU-2 showed a diverse array of capabilities, including the synthesis of Gibberellins, Extracellular Polymeric Substances, Siderophores, and Hydrogen Cyanide along with nitrogen xation and ammonia production. The microbe could e ciently tolerate 45% PEG-6000 concentration and effectively produce IAA in 15% PEG concentration. It could also tolerate high concentration of Cr (VI) and synthesize IAA even in 50 ppm Cr (VI). The ndings of this study provide valuable insights into harnessing the potential of indigenous microorganisms to promote plant growth, enhance soil fertility, and establish sustainable agricultural practices essential for restoring the health of ecosystems.