Taxonomic revision of the acidophilic genus Acidiella (Dothideomycetes, Capnodiales) with a description of new species from Poland

Acidophilic fungi are characterized by their ability to tolerate very low pH conditions and to grow optimally below pH 5. The genus Acidiella (Dothideomycetes, Capnodiales, Teratosphaeriaceae) comprises acidophilic and acidotolerant fungi that are commonly distributed in highly acidic soils, drainages and waters worldwide. This study revises Acidiella taxonomy and provides alternative DNA barcodes. The morphological characteristics were revaluated by the investigation of conidial ontogeny, and knowledge of the ecology and biogeography of the genus is summarized. The new species Acidiella polonica isolated from highly acid (pH 2.7-3.8) technogenic soil developed on mine spoils in Poland is described here. This species is distinguishable by genetic markers, morphology and its ability to grow at pH 1. Based on DNA sequence and morphological comparisons, we also show that Acidiella uranophila (syn. Fodinomyces uranophilus) is a synonym of Acidiella bohemica. Among all species, A. bohemica is the most commonly isolated and is widely distributed over four continents. Interestingly, its distribution at the global scale is limited to extremely acidic substrates (pH < 4.0), often with high heavy metal toxicity, where it represents a dominant proportion of the mycobiota. Previous studies have also indicated its biotechnological potential in the bioaccumulation of rare earth elements and in mycoremediation. Other species are rare, and as in the case of A. americana and two undescribed species, they can also occur in non-acidic pH environments.