# Fungi and Arsenic: Tolerance and Bioaccumulation by Soil Saprotrophic Species
## 1 Introduction
Most fungi can produce hydroxamate-type siderophores, but other types have also been observed including rhizoferrin, a polycarbonate siderophore, in Zygomycetes and phenolate compounds in other fungi [28; 29; 26]. Evidence has shown that since microorganisms can also acquire Fe from As-bearing minerals (es. Scorodite), consequently increasing the As mobilization, siderophore production can correlate with increased As resistance, even if a direct link to the siderophores' action binding As was not observed [25]. The potential of siderophores in the bioremediation of potentially toxic elements is very high, as siderophore-producing fungi are abundant in soils, and siderophores can strongly influence speciation, bioavailability, and the fate of metals, metalloids, and radionuclides in the environment [26]. Therefore, since siderophores represent a useful tool, in order to deepen the tested species potential in As bioremediation, siderophore production was taken into account. In this context, four fungal species, _Absidia spinosa_ [PERSON], _Cephalotrichum nanum_ ([PERSON]. [PERSON], _Metrahizium marquandii_ ([PERSON]) [PERSON], [PERSON], and _Purpurerocillium lilacinum_ ([PERSON] [PERSON], [PERSON], [PERSON], previously isolated from Italian soils with naturally high As concentrations, were investigated in the presence of As, as As(III) or arsenite, in two different nutritional conditions. In fact, fungi are strongly influenced by nutritional condition in their growth and ecology and therefore also in their ability to tolerate stresses. Furthermore, medium composition may have an effect on metal uptake [30; 31]. To our best knowledge, these species have not been previously studied for their ability to tolerate and accumulate As, but their potential in the bioremediation of some toxic metals has been reported [32; 33; 34; 35; 36; 37; 38; 39]. In particular, [PERSON] et al. [32] reported on the tolerance and solubilization of zinc compounds by _A. spinosa_, as fungal species associated with _Thlaspi caerulescens. A. spinosa_, and _P. lilacinum_ adsorbed plutonium onto mycelium and spores [33]. _P. lilacinum_ was reported to be tolerant to and accumulate Pb, Cd, and Cr [34; 35; 36; 37], while _M. marquandii_ resulted tolerant to Zn and Pb and able to uptake them [38; 39]. No species of the genus _Cephalotrichum_ was previously tested with metals. However, being oligotrophic fungi, these species inhabit extreme habitats with low availability of nutrients, for example, _C. stemoitis_ has been isolated from a closed gold mine with high As concentrations [40; 41]. Hence, these four fungi show a great potential for the development of biotechnological applications for As remediation, and consequently the knowledge of their interactions with arsenic deserves to be deepened. Therefore, to shed further light on this topic, this study was aimed to investigate the (1) fungal tolerance to high As concentrations; (2) arsenic bioaccumulation in fungal biomass; (3) influence of As presence in the medium on the uptake and accumulation of other elements; and (4) the production of siderophores and their affinity for As compared to that for Fe.