Abstract:A pot experiment was conducted to investigate the effects of L6 (Halomonas sp.) on cotton growth, rhizosphere soil physicochemical properties and soil microorganisms under saline-alkali stress.Fermentation conditions were optimized to enhance strain activity.The results showed that compared with CK, cotton growth in germination rate, stem length, and fresh weight increased by 21.88%, 15.11%, and 23.35%, respectively (P<0.05).L6 alleviated the detrimental effects of saline-alkali stress by reducing leaf malondialdehyde (MDA) content by 13.61% (P<0.05) and increasing proline (PRO) content and phenylalanine ammonia-lyase (PAL) activity by 10.12% and 13.04%, respectively (P<0.05).Moreover, L6 improved the rhizosphere soil environment by decreasing electrical conductivity by 7.69% and increasing organic matter content by 5.82%.The Biolog microplate analysis revealed that treatment with L6t increased the Shannon diversity index of soil microbial communities by 14.40% (P<0.05) and enhanced the community’s utilization of carbohydrates, amino acids, carboxylic acids, and phenolic acids.To further improve the activity of the strain, fermentation medium and culture conditions for strain L6 were optimized using single factor experiment, response surface methodology.The optimal medium composition included sucrose (23.61 g/L), beef extract (17.94 g/L), and MgSO4 (8.41 g/L).Optimal culture conditions were determined as pH 7.0, 2% (w/v) NaCl, temperature 28 ℃, inoculum size 2%, rotational speed 160 r/min, liquid volume 50 mL/500 mL flask, and incubation time 14 hours.Under these conditions, the viable bacterial count reached 2.5×1010 cfu/mL, representing a significant 56.25% increase compared to the original formulation (P<0.05).Pot experiments showed that the optimized bacterial suspension soaking significantly increased the germination rate, stem length, root length, and fresh weight of cotton by 85.71%, 12.60%, 39.53%, and 33.33%, respectively, compared to unoptimized strain (P<0.05).These findings, indicate that Halomonas.sp L6 holds significant potential as a high-efficiency microbial resource for industrial-scale microbial agent production and the remediation of saline-alkali soils in Xinjiang. |