Specific detection of Lysobacter antibioticus strains in agricultural soil using PCR and real-time PCR

Bacillus megaterium NCT-2 agent alters soil nutrients, vegetable quality, and root microecology in secondary salinized soil

Microbial remediation technology has the characteristics of high efficiency and environmental protection, which has attracted attention. However, there is complexity in the microorganism-soil-plant system. The effects of microbial agents on soil nutrients, plant quality, rhizosphere, and endophytic microorganisms are still unclear. Here, we demonstrate the application of Bacillus megaterium NCT-2 as a multifunctional agent that concurrently addresses salinization-driven nutrient imbalances and reshapes keystone microbial taxa to restore soil-plant homeostasis. The results showed that NCT-2 agent improved the soil nutrients, reduced the loss of nitrogen and sulfur, increased the content of available phosphorus, and decreased the electrical conductivity. The agent increased the number of bacteria and fungi in the soil. Meanwhile, NCT-2 agent improved the vegetable quality and yield. Specifically, the NCT-2 agent significantly increased the aboveground fresh weight, underground fresh weight, total flavonoids, antioxidant enzyme activity, ascorbic acid, Cu, Zn, Fe, P, and K in lettuce, while significantly reduced nitrate. The chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll were significantly increased by the agent. Critically, high-throughput sequencing revealed NCT-2-driven enrichment of stress-resilient taxa (e.g., Firmicutes, Acidobacteria) and functional synergists (e.g., Acetobacter), which correlated with soil nutrient fluxes and plant antioxidant capacity. By decoupling the interplay between microbial community restructuring and systemic remediation outcomes, this work establishes a novel framework for leveraging keystone taxa to optimize salinized agroecosystems.

Effect of culture medium optimization on the secondary metabolites activity of Lysobacter antibioticus 13-6

Fermentation products of Lysobacter antibioticus 13-6 have antagonistic activity against devastating phytopathogenic bacerium Xanthomonas oryzae pv. oryzicola. The production of Lysobacter antibioticus 13-6 secondary metabolites was increased by optimizing the fermentation medium; using a single-factor screening test, Plackett-Burman Design, and Box-Behnken Design. The medium's final formulation for active secondary metabolites high-yield included peptone 5 g/L, glucose 4.73 g/L, MgSO₄·7H₂O 2.33 g/L, and K₂HPO₄ 2.21 g/L. We compared phenazine-1-carboxylic acid (PCA) contents of L. antibioticus 13-6 in the initial and optimized mediums through HPLC. It was found PCA contents of the optimized medium are two folds more than in the initial medium. We also detected the relative expression of five phenazine genes of L. antibioticus 13-6 via RT-qPCR, and it was found that genes: phzB, C, S, and NO1 have more significant expression compared with the initial medium, while gene phzD has found just significant. Further, we revealed that the optimal fermentation conditions for secondary metabolites were: fermentation time 60 hours, shaking speed 160 rpm, inoculum size 3%, and the initial pH = 7.0. In the end, it was determined that the antimicrobial activity and quality of L. antibioticus 13-6 secondary metabolites were increased by about 41.75% and 2-times, respectively, after the optimization of the fermentation medium.