Soil desertification is an important challenge in global soil management, and effectively and stably restoring soil function is an urgent problem. Using synthetic microbial communities (SynComs) is a burgeoning microbial strategy aimed at enhancing soil nutrients through functional synergies among diverse microorganisms; nevertheless, their effectiveness in restoring desertified soils remains unknown. In this study, we conducted a two-year field experiment using a SynCom constructed by in situ probiotic bacteria and set up control, chemical fertilizer, and combined SynCom–chemical fertilizer (combined fertilizer) treatments to investigate the linkage between microbial communities and soil multifunctionality in the soil surface layer (0–10 cm). Both the bacterial and fungal communities differed the most under the combined fertilizer treatment compared to the control. The bacterial communities differed more under treatments of the SynCom than the chemical fertilizer, while the fungal communities differed more under the chemical fertilizer treatment than the SynCom treatment. Regarding soil function, the SynCom strengthened the correlation between enzyme activities and both bacterial communities and functional properties. pH and available potassium were the main influencing factors under the chemical fertilizer and combined fertilizer treatments. The beta-diversity of the bacterial communities was significantly correlated with soil multifunctionality. Random forest analyses showed that the SynCom significantly enhanced the bacterial communities, driving soil multifunctionality, and that some potential microbial taxa drove multiple nutrient cycles simultaneously. In summary, the SynCom effectively increased the abundance of most carbon, nitrogen, and phosphorus functional genes as well as soil enzyme activities. The bacterial community composition contributed significantly to soil multifunctionality. Hence, the development of novel microbial agents holds significant potential for improving soil functionality and managing desertification.

In order to reveal the effect of Autoinducer-2 (AI-2) quorum sensing signal on rumen bacterial community under roughage substrates with significant differences in chemical composition (oat straw has high lignocellulose and low crude protein, Suaeda salsa straw has higher crude protein and soluble carbohydrate content, and ash salt content). In this study, oat straw and Suaeda salsa straw were used as substrates, combined with in vitro batch culture fermentation and AI-2 addition treatment, the changes of bacterial community structure, interaction network, predicted metabolic function and xylanase activity were systematically analyzed. The community structures of the oat straw and Suaeda salsa systems differed significantly, and their disparities amplified across serial subcultures. Regulation of AI-2 on the communities showed obvious substrate dependence: in the oat system, AI-2 significantly reshaped the community structure and increased species diversity, whereas in the Suaeda salsa system, it showed a opposite trend. Network analysis showed that AI-2 treatment reduced community connectivity and increased the proportion of negative correlation edges, indicating that it could affect community stability by reconstructing competition and cooperation among species. Functional prediction and enzyme analysis revealed AI-2 enriched carbon metabolism pathways and raised xylanase activity across both substrates, with distinct regulated metabolic pathways observed in the two substrate cultures. This study provides a new perspective for understanding bacterial community succession regulated by quorum sensing signals in in vitro culture systems.