Aciditerrimonas ferrireducens gen. nov., sp. nov., an iron-reducing thermoacidophilic actinobacterium isolated from a solfataric field.

An iron-reducing, moderately thermophilic, acidophilic actinobacterium, strain IC-180(T), isolated from a solfataric field in Hakone, Japan, was subjected to polyphasic taxonomic analysis. Strain IC-180(T) was a motile, short rod-shaped, Gram-positive bacterium that was able to grow at temperatures of 35-58 °C (optimally at 50 °C) and at pH 2.0-4.5 (optimally at pH 3.0). The strain grew aerobically and heterotrophically. It also grew anaerobically or autotrophically by dissimilatory reduction of ferric iron. No oxidation of ferrous iron was observed. Major cellular fatty acids detected were iso-C(16 : 0), anteiso-C(17 : 0) and iso-C(18 : 0); the major menaquinone was MK-9(H(8)). Phosphatidyl-N-methylethanolamine and an unknown ninhydrin-positive phosphoglycolipid were detected. The total DNA G+C content was 74.1 mol%. 16S rRNA gene sequence comparisons revealed that strain IC-180(T) was a member of the order Acidimicrobiales and clustered coherently with uncultured actinobacteria from a geothermal site and a bioreactor operated under moderately thermophilic conditions. This cluster could be distinguished from the two other clusters comprising the families of this order, Acidimicrobiaceae and Iamiaceae, respectively. Based on the properties of strain IC-180(T) determined in this polyphasic taxonomic study, this strain represents a novel species in a new genus in the order Acidimicrobiales, for which the name Aciditerrimonas ferrireducens gen. nov., sp. nov. is proposed; the type strain is IC-180(T) ( = JCM 15389(T)  = DSM 45281(T)).