Cebrián Eva, Roncero Elia, Delgado Josué, Núñez Félix, Rodríguez Mar
Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain.
Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain.
Int J Food Microbiol. 2023 Nov 16;405:110342. doi: 10.1016/j.ijfoodmicro.2023.110342. Epub 2023 Jul 27.
Penicillium nordicum is one of the major producers of ochratoxin A (OTA) in dry-cured ham. Staphylococcus xylosus Sx8 and Staphylococcus equorum Se31 have been previously proposed as biocontrol agents (BCAs) to prevent the OTA contamination, although their antifungal mode of action has not been established yet. Thus, the aim of this work was to elucidate their mode of action against P. nordicum in a dry-cured ham model system. For this, the effect of live cells, dead cells, and cell-free broth; the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays, antifungal effect of volatile compounds, OTA detoxification, and effect on fungal proteome were determined. No fungal growth was observed after 14 days of co-culture with live cells of each staphylococcus at 15 or 20 °C. However, such inhibition was not observed with either dead cells or extracellular extracts. The number of carbon sources utilised by P. nordicum was higher than those used by both cocci at 20 °C, whilst the opposite occurred at 15 °C. According to NOI, nutritional dominance depends on temperature, at 20 °C P. nordicum dominated the niche, but at 15 °C the mould is dominated by the BCAs. The volatile pattern generated by each coccus did not show antifungal effect, and both staphylococci failed to degrade or adsorb OTA. However, in the interaction assay, S. xylosus and S. equorum were able to decrease the fungal growth and its OTA production. In addition, proteomic analyses showed changes in the abundance of proteins related to the cell wall integrity (CWI), carbohydrate metabolism and the biosynthesis of secondary metabolites such as OTA. In conclusion, overall, the antagonistic effects of the two studied cocci against P. nordicum are greater at 15 °C than at 20 °C, being linked to competition for space and nutrients, triggering alterations in CWI pathway, OTA biosynthesis, and carbohydrate metabolism.
北欧青霉是干腌火腿中赭曲霉毒素A（OTA）的主要产生菌之一。木糖葡萄球菌Sx8和马胃葡萄球菌Se31此前已被提议作为生物防治剂（BCAs）来预防OTA污染，尽管它们的抗真菌作用模式尚未确定。因此，本研究的目的是在干腌火腿模型系统中阐明它们对北欧青霉的作用模式。为此，测定了活细胞、死细胞和无细胞肉汤的作用；营养利用模式、生态位重叠指数（NOI）、双培养试验中的相互作用、挥发性化合物的抗真菌作用、OTA解毒作用以及对真菌蛋白质组的影响。在15或20℃下与每种葡萄球菌的活细胞共培养14天后，未观察到真菌生长。然而，死细胞或细胞外提取物均未观察到这种抑制作用。在20℃时，北欧青霉利用的碳源数量高于两种球菌，而在15℃时情况则相反。根据NOI，营养优势取决于温度，在20℃时北欧青霉占据生态位，但在15℃时霉菌被生物防治剂占据主导。每种球菌产生的挥发性模式未显示出抗真菌作用，且两种葡萄球菌均未能降解或吸附OTA。然而，在相互作用试验中，木糖葡萄球菌和马胃葡萄球菌能够抑制真菌生长及其OTA产生。此外，蛋白质组学分析表明，与细胞壁完整性（CWI）、碳水化合物代谢以及OTA等次生代谢物生物合成相关的蛋白质丰度发生了变化。总之，总体而言，两种研究的球菌对北欧青霉的拮抗作用在15℃时比在20℃时更强，这与空间和营养竞争有关，引发了CWI途径、OTA生物合成和碳水化合物代谢的改变。
