Research on the Potential Mechanism of Guanine Nucleotides Enhancing the Tolerance of Lactiplantibacillus plantarum Y12

This study aims to elucidate the mechanism by which exogenous guanosine monophosphate (GMP) enhances the stress tolerance of Lactiplantibacillus plantarum Y12. Phenotypic assays demonstrated that GMP supplementation significantly improved biofilm formation, adhesion index, and auto-aggregation ability. The survival ability of Y12 in simulated gastric juice, intestinal juice, and freeze-drying stress was also significantly increased. Transcriptomic results revealed that GMP increased the intracellular content of the second messengers C-di-AMP and C-di-GMP by reducing phosphodiesterase (PDE, RS04640). This, together with the upregulated expression of luxR and rpoN, synergistically promoted biofilm formation. Furthermore, GMP enhanced acid tolerance by increasing glutamate decarboxylase activity (GAD, RS05235). It also significantly elevated the levels of extracellular proteins, exopolysaccharides, membrane polysaccharides, and membrane fatty acids by modulating genes related to proteins (yidC, yajC), polysaccharides (agaB, agaC), and membrane fatty acid synthesis (RS02005, plsY), which was also demonstrated by quantitative determination. Collectively, these regulatory mechanisms substantially improve the stress tolerance of L. plantarum Y12, providing a theoretical basis for its application.