Nature's Hat-trick: Can we use sulfur springs as ecological source for materials with agricultural and medical applications?

•Sulfur-rich waters from two mineral wells exhibit activity against Steinernema feltiae and Candida albicans.•Sulfur particles, produced by milling, are active against HCT-116 colon cancer cells.•Similar tellurium particles are active against HCT-116 cells.•Sulfide-rich waters provide a sustainable source of sulfur species applicable in agriculture and possibly also in medicine.

Sulfur and its various compounds play a major role in agriculture and medicine. Natural waters rich in hydrogen sulfide may therefore be seen as a sustainable resource for biologically active sulfur species. By sampling such waters from two readily accessible mineral wells in Germany, we are able to show that such waters exhibit interesting nematicidal and antimicrobial activity which may be used in an agricultural context. Whilst applications in the field of agriculture could, in theory, result in an amalgamation of irrigation, soil enrichment and phyto-protection, therapeutic uses are more complex and complicated by the many physiological effects associated with hydrogen sulfide and its oxidized derivatives. The latter may include polysulfides (Sx2-) as well as small sulfur particles. Indeed, we have recently noted significant cytotoxic properties of clean, mechanically produced sulfur nanoparticles against HCT-116 colon cancer cells. Since sulfur-rich natural waters are known to deposit elemental sulfur upon oxidation, they may therefore be used as a natural (re)source of sulfur particles, possibly obtained by direct oxidation on air, mild oxidation with sulfur dioxide or enzymatic oxidation employing Thiobacillus. A similar biotechnological approach involving Staphylococcus carnosus and selenite (SeO32−) produces biologically active selenium nanoparticles of excellent quality and with a pronounced biological activity. Eventually, natural spa waters rich in sulfide seem to open up various interesting opportunities in medicine and eco-friendly agriculture.

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