We investigated the growth-promoting mechanism of salt-tolerant plant growth promoting rhizobacteria (ST-PGPR) in wheat under sodium chloride (NaCl) stress by measuring the growth and physiological and biochemical responses of wheat plants inoculated with ST-PGPR under 0–400 mM NaCl. The results showed that ST-PGPR plays a significant role in the growth of wheat under NaCl stress. Under 300 mM NaCl, wheat plants inoculated with the three ST-PGPR strains increased in plant height, root length, dry weight, and fresh weight by 71.21%, 89.19%, 140.94%, and 36.31%, respectively, compared to the control group. The proline and soluble sugar contents of wheat inoculated with Bacillus thuringiensis increased by 38.8% and 21.4%, respectively. The average content of antioxidant enzymes increased by 13.89%, and compared with the control, in wheat inoculated with the three species of ST-PGPR, the average content of ethylene decreased 2.16-fold. In addition, a mathematical model based on the “interaction equation” revealed that the best results of mixed inoculation were due to the complementary strengths of the strains. The analysis of experimental phenomena and data revealed the mechanisms by which Brevibacterium frigoritolerans, Bacillus thuringiensis, and Bacillus velezensis alleviate NaCl stress in wheat: (1) by lowering of osmotic stress, oxidative stress, and ethylene stress in wheat and (2) by using root secretions to provide substances needed for wheat. This study provides a new approach for the comprehensive understanding and evaluation of ST-PGPR as a biological inoculant for crops under salt stress.

Rice paddies are a major source of agricultural greenhouse gas emissions, primarily caused by the proliferation of anaerobic, methanogenic bacteria during prolonged inundation. Phototrophic bacteria utilize light energy for metabolism and are potential candidates for carbon and nitrogen fixation, and reduction of methane gas emissions. We investigated the effect of applying the phototrophic bacterium Rhodopseudomonas palustris (PNSB) during the cropping period on soil organic carbon (SOC) and methane emissions for second-crop rice in the Tainan Guantian region. In the experimental group, PNSB was applied five times during the rice cultivation period. Compared to the control group, the experimental group demonstrated a significant reduction in methane emissions, especially in the tillering stage, where emissions averaged 37.26 ± 12.97 g-CH₄/m²/season compared to 49.48 ± 25.06 g-CH₄/m²/season of the control group. Over the entire growing season, the experimental group reduced the emission of 3.05 Mg·CO₂e/ha. Additionally, administering PNSB improved soil carbon sequestration, from 4.89 tons-C/ha in the control group to 17.45 tons-C/ha. The phototrophic bacterium PNSB was beneficial for soil carbon sequestration and reducing greenhouse gas emissions. However, further research is required to optimize the methodology of applying phototrophic bacteria for agricultural purposes.

Agroecosystems play a crucial role in carbon sequestration and reducing atmospheric CO₂ emissions by storing organic carbon in soil. Soil fertility and productivity are essential for global crop demands and depend on soil organic matter, particularly humic substances (HS). HS is crucial for soil health and carbon sequestration as it involves the carbon cycle, supplies nutrients for plants, and reduces the emission of pollutants through microbial processes for the enhancement of CO₂ sequestration. Humification is a natural process of organic matter stabilization, playing a crucial role in maintaining soil organic content and carbon storage. Laccase is used to polymerize monomeric compounds such as phenols and their derivatives into highly polymerized HS. We screened five cellulose-degrading isolates, among which three strains demonstrate lignin-degrading capabilities. WSC-7 exhibited the highest laccase activity and showed a high similarity [99.51%] to Arthrobacter defluvii based on 16S rDNA analysis. Strain LiPK-078-5 in nutrient broth medium and WSC-7 in Difco Sporulation Medium exhibited optimal catalytic activity for catechol, indicating their efficiency for aromatic polymerization of soluble organic carbon. The addition of rice husk biochar with strains LiPK-078-5, WSC-6, and WSC-7 increased organic carbon content effectively. The synthesis of humic substances in soil through microbial processes increases soil carbon sequestration and reduces greenhouse gas emissions in the environment.

Livestock wastewater is an important source of nitrogen pollution, but it also represents a potential feedstock for nitrogen recovery. In this study, longan wood-derived biochar was used as an immobilization carrier in a bio-ammonification system developed with aerobic and facultative ammonifying bacteria isolated from swine wastewater. The system was designed to enhance microbial retention and promote the conversion of organic nitrogen into ammonium concentration (NH₄⁺-N) under oxygenated conditions. Among the tested strains, Lysinibacillus sp. (strain 4-1) showed the highest ammonification activity, reaching an NH₄⁺-N concentration of 340 mg/L in NB medium within 5 days. In sterilized swine wastewater, the biochar-immobilized strain 4-1 achieved 47.17% organic nitrogen removal. The results suggest that coupling microbial ammonification with biochar immobilization may provide a low-carbon approach for nitrogen recovery from livestock wastewater and facilitate decentralized bio-ammonia production.