# Fungi and Arsenic: Tolerance and Bioaccumulation by Soil Saprotrophic Species
## 4 Discussion
Conversely, all the tested species released siderophores with an Fe affinity. _A. spinosa_ along with _P. ilacinum_ showed the highest affinity for Fe complexation since the 14 days of growth reading, with _A. spinosa_ showing a slight reduction of chelation at 21 days. A reduction in the effectiveness of Fe chelation over growth time was also observed in _C. nanum_, which showed the lowest OD values at seven days. The efficacy of _A. spinosa_ in chelating Fe agrees with the fact that is reported in literature, which is to produce bacteriocin[89]. This special siderophore belongs to the carboxylate type of siderophores, generally produced by Zygomycetes. Despite this varying according to the species, it has been observed for _Petromyes alliacus_ that its siderophores have a better affinity for Fe than for other tested metals and metalloids [27]. The highest ability of _A. spinosa_ and _P. ilacinum_ in Fe complexation was confirmed by the higher Fe accumulation in the fungal biomass of these strains (Supplementary Materials Table S1), which were found to be the species with the highest concentrations of Fe, thus confirming their efficacy in chelating Fe. Furthermore, in _A. spinosa_ biomass were found the highest concentrations of P, this may be explained by the known ability of Mucorales to accumulate P as polyphosphates, which serves as a phosphate store [90] and as chelators for metals and metalloids [91]. In conclusion, the tested fungal species were tolerant to high concentrations of arsenic. In most of the cases, the nutritional conditions did not influence the tolerance to arsenic. Therefore, the tested fungal species are promising novel candidates for future scale-up studies in As mycoremediation. Considering their potential in As bioaccumulation, these species can be new tools in biotechnological applications (e.g., As recovery). Moreover, from our results, it emerged that these species can uptake other potentially toxic elements such as antimony, which have a strategic importance for industrial and high-tech applications. The production of siderophores with high affinity for Fe has been observed. Considering that siderophores may be involved in the process of tolerance and bioaccumulation, further research is needed to evaluate an eventual release of siderophores with As affinity triggered by As exposure. Finally, this study also led to results that have a potential ecological significance with respect to the role of fungi in arsenic geochemistry and its cycle in ecosystems. The following are available online at [[http://www.mdpi.com/2076-3417/10/9/3218/s1](http://www.mdpi.com/2076-3417/10/9/3218/s1)]([http://www.mdpi.com/2076-3417/10/9/3218/s1](http://www.mdpi.com/2076-3417/10/9/3218/s1)), Table S1: Element concentrations in fungal biomass, Table S2: Scores and loadings of the five significant components obtained by the PCA performed on the element concentrations in fungal biomass of the tested species. **Author Contributions:** Conceptualization, A.M.P., A.C., and V.S. ; Formal analysis, A.C., V.S., and L.M. ; Investigation, A.C., V.S., and L.M. ; Resources, A.M.P. and S.C.; Writing--original draft preparation, A.C., V.S., and L.M. ; Writing--review and editing, A.M.P. and S.C.; Visualization, A.C., V.S., and L.M. ; Supervision, A.M.P. and S.C.; Project administration, A.M.P. and S.C.; Funding acquisition, A.M.P. and S.C. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Conflicts of Interest:** The authors declare no conflicts of interest.