Acidiferrimicrobium australe gen. nov., sp. nov., an acidophilic and obligately heterotrophic, member of the actinobacteria that catalyses dissimilatory oxido-reduction of iron isolated from metal-rich acidic water in Chile

A novel acidophilic member of the phylum Actinobacteria was isolated from an acidic, metal-contaminated stream draining from an abandoned underground coal mine (Trongol mine), situated close to Curanilahue, Biobío Region, Chile. The isolate (USS-CCA1^T) was demonstrated to be a heterotroph that catalysed under aerobic conditions the oxidation of ferrous iron and the reduction of ferric iron under anaerobic conditions, but not the oxidation of sulfur nor hydrogen. USS-CCA1^T is a Gram-positive, motile, short rod-shaped, mesophilic bacterium with a temperature growth optimum at 30 °C (range 20–39 °C). It was catego-rized as an extreme acidophile growing between 1.7 and 4.5 and optimally at pH 3.0. The G+C content of the chromosomal DNA of the isolate was 74.1 mol%, which is highly related to Aciditerrimonas ferrireducens IC-180^T, (the most closely related genus; 94.4% 16S rRNA gene identity), and higher than other acidophilic actinobacteria. The isolate (USS-CCA1^T) was shown to form a distinct 16S rRNA clade from characterized acidophilic actinobacteria, well separated from the genera Acidimicrobium, Ferrimi-crobium, Ferrithrix, ‘Acidithrix’ and Aciditerrimonas. Genomic indexes (ANIb, DDH, AAI, POCP) derived from the USS-CCA1^T draft genome sequence (deposited at DDBJ/ENA/GenBank under the accession WJHE00000000) support assignment of the isolate to a new species and a new genus within the Acidimicrobiaceae family. Isolate USS-CCA1^T is the designated type strain of the novel species Acidiferrimicrobium australe (=DSM 106828^T,=RGM 2506^T).