Extremophilic bacteria restrict the growth of Macrophomina phaseolina by combined secretion of polyamines and lytic enzymes

[EN] Extremophilic microorganisms were screened as biocontrol agents against two strains of Macrophomina phaseolina (Mp02 and 06). Stenotrophomonas sp. AG3 and Exiguobacterium sp. S58 exhibited a potential in vitro antifungal effect on Mp02 growth, corresponding to 52.2% and 40.7% inhibition, respectively. This effect was confirmed by scanning electron microscopy, where images revealed marked morphological alterations in fungus hyphae. The bacteria were found to secrete lytic enzymes and polyamines. Exiguobacterium sp. S56a was the only strain able to reduce the growth of the two strains of M. phaseolina through their supernatant. Antifungal supernatant activity was correlated with the ability of bacteria to synthesize and excrete putrescine, and the exogenous application of this polyamine to the medium phenocopied the bacterial antifungal effects. We propose that the combined secretion of putrescine, spermidine, and lytic enzymes by extremophilic microorganism predispose these microorganisms to reduce the disease severity occasioned by M. phaseolina in soybean seedlings. The authors acknowledge the generous financial support by the PICT V Bicentenario 2010 1788 Project (FONCyT, Argentina). This work was performed in the context of a project called ¿Análisis de Adaptación al Cambio Climático en Humedales Andinos¿. ID: 6188775¿8-LP13. Ministerio del Medio Ambiente, Región de Antofagasta. We are also grateful to Lic. C. Pérez Brandan for providing us with the M. phaseolina strains used in this study. Santos, AP.; Nieva Muratore, L.; Sole-Gil, A.; Farías, ME.; Ferrando Monleón, AR.; Blazquez Rodriguez, MA.; Belfiore, C. (2021). Extremophilic bacteria restrict the growth of Macrophomina phaseolina by combined secretion of polyamines and lytic enzymes. Plant Biotechnology Reports. 32:1-9. https://doi.org/10.1016/j.btre.2021.e00674