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

<jats:p>A novel acidophilic member of the phylum <jats:italic>
<jats:named-content content-type="phylum">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.5711" xlink:type="simple">Actinobacteria</jats:ext-link>
</jats:named-content>
</jats:italic> 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<jats:sup>T</jats:sup>) 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<jats:sup>T</jats:sup> is a Gram-positive, motile, short rod-shaped, mesophilic bacterium with a temperature growth optimum at 30 °C (range 20–39 °C). It was categorized 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 <jats:italic>
<jats:named-content content-type="species">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.21808" xlink:type="simple">Aciditerrimonas ferrireducens</jats:ext-link>
</jats:named-content>
</jats:italic> IC-180<jats:sup>T</jats:sup>
<jats:italic>,</jats:italic> (the most closely related genus; 94.4 % 16S rRNA gene identity), and higher than other acidophilic actinobacteria. The isolate (USS-CCA1<jats:sup>T</jats:sup>) was shown to form a distinct 16S rRNA clade from characterized acidophilic actinobacteria, well separated from the genera <jats:italic>
<jats:named-content content-type="genus">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.5717" xlink:type="simple">Acidimicrobium</jats:ext-link>
</jats:named-content>
</jats:italic>, <jats:italic>
<jats:named-content content-type="genus">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.14255" xlink:type="simple">Ferrimicrobium</jats:ext-link>
</jats:named-content>
</jats:italic>, <jats:italic>
<jats:named-content content-type="genus">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.14257" xlink:type="simple">Ferrithrix</jats:ext-link>
</jats:named-content>
</jats:italic>, <jats:italic>‘Acidithrix’</jats:italic> and <jats:italic>
<jats:named-content content-type="genus">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.21807" xlink:type="simple">Aciditerrimonas</jats:ext-link>
</jats:named-content>
</jats:italic>. Genomic indexes (ANIb, DDH, AAI, POCP) derived from the USS-CCA1<jats:sup>T</jats:sup> 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 <jats:italic>
<jats:named-content content-type="family">
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.5716" xlink:type="simple">Acidimicrobiaceae</jats:ext-link>
</jats:named-content>
</jats:italic> family. Isolate USS-CCA1<jats:sup>T</jats:sup> is the designated type strain of the novel species <jats:italic>Acidiferrimicrobium australe</jats:italic> (=DSM 106828<jats:sup>T</jats:sup>,=RGM 2506<jats:sup>T</jats:sup>).</jats:p>