Impaired bioenergetic response mediates the antifungal effect of lipopeptides from Bacillus tequilensis EA-CB0015 and cinnamon extract against Fusarium oxysporum f. sp. cubense

Abstract

Lipopeptides (LPs) from B. tequilensis EA-CB0015 have antifungal activity against Fusarium species. Specifically, against F. oxysporum f. sp. cubense (Foc), the cause of the Fusarium wilt of banana. In addition, cinnamon (CN) extract is also known for its inhibitory activity against the Fusarium genus. The main goal of this research was to determine if the effect of LPs, CN extract or their combination against Foc is related to an impairment of mitochondrial function. Our results show that biomass decreased by 74% (p < 0.0001) and 84% (p < 0.0001) when cultures were treated with 128 ppm LPs and 152.5 ppm CN extract, respectively. In parallel, we found a pronounced impairment of the bioenergetic response. That is, the routine oxygen consumption rate diminished by 55% (p = 0.0148) and 38% (p < 0.0001), respectively. Moreover, the ATP-linked respiratory rate decreased by 63% (p = 0.0461) and 44% (p = 0.0005), while the FCCP-simulated respiratory rate by 63% (p = 0.0255) and 45% (p = 0.0002). Therefore, our data suggest that the altered bioenergetic response observed in cultures of Foc treated with LPs or CN is mainly caused by an impairment of the activity of the ETC components. On the other hand, biomass production was reduced by 80% (p < 0.0001) when cultures were treated with a mixture comprising only 10% LPs and 40% CN extract. Furthermore, ATP-linked and FCCP-stimulated respiratory rates decreased by 62% (p = 0.0024) and 68% (p < 0.0001), respectively under the same conditions. A potentially synergistic antifungal effect of cyclic LPs with a CN extract is suggested.