Microbial consortium involving Pseudomonas and Bacillus: strain selection and the effect of co-cultivation on biocontrol activity against phytopathogens and the composition of metabolic extracts.

Agricultural sustainability is vital to meet the growing global demand for food; therefore, the search for more sustainable options to replace traditional chemical products has gained attention due to their benefits. The sector has applied innovative microbial consortium approaches as a niche for exploring new bioproducts and metabolic pathways through microbial interactions. Thus, this study sought to select two endophytic bacterial strains with biocontrol activity to study their metabolic interactions in culture. For this, co-cultivation and axenic culture assays were carried out to evaluate the inhibition of Corynespora cassiicola, Sclerotinia sclerotiorum, Moniliophthora perniciosa, and Colletotrichum truncatum. After the production of antiphytopathogenic compound tests, two strains were selected: P. putida MG36 and B. amyloliquefaciens SS14. These bacteria were cultivated under three distinct conditions: axenic cultivation of SS14, axenic cultivation of MG36, and co-cultivation. The metabolites were extracted and analyzed by liquid chromatography coupled with mass spectrometry (UHPLC-MS/MS). The results showed that both strains exhibited significant antifungal activity. B. amyloliquefaciens SS14 demonstrated 65% inhibition against C. truncatum, while P. putida MG36 showed 58% inhibition against S. sclerotiorum. Analysis of the chemical profiles revealed the presence of exclusive and shared metabolites, such as iturin A4 (antifungal lipopeptide) and macrolactin A (bioactive polyketide), under different culture conditions. In conclusion, P. putida MG36 and B. amyloliquefaciens SS14 show promise as biocontrol agents against phytopathogens, contributing to more sustainable agricultural practices.