Phenylobacterium ferrooxidans sp. nov., isolated from a sub-surface geothermal aquifer in Iceland

A novel bacterial strain, HK31-G^T, was isolated from a subsurface geothermal aquifer (Hellisheidi, SW-Iceland) and was characterized using a polyphasic taxonomic approach. Phylogenetic analysis of 16S rRNA gene along with phylogenomic position indicated that the novel strain belongs to the genus Phenylobacterium. Cells are motile Gram-negative thin rods. Physiological characterization showed that strain HK31-G^T is a mesophilic bacterium able to grow from 10 to 30 °C, at pH values between 6 and 8 and at NaCl concentrations between 0 and 0.5 %. Optimal growth was observed without sodium chloride at 25 °C and pH 6. Strain HK31-G^T is chemoorganoheterotroph and its major saturated fatty acids are C_18:1ω7c, C₁₆_:1ω6c and C_16:0, the predominant quinone is Q-10 and the major polar lipid is phosphatidylglycerol. The new strain also possesses the capacity to use ferrous iron (Fe(II)) as the sole energy source and can also be considered as a chemolithoautotrophic microorganism. The overall genome of strain HK31-G^T was estimated to be 4.46 Mbp in size with a DNA G + C content of 67.95 %. Genes involved in iron metabolism were identified, but no genes typically involved in Fe(II)-oxidation were found. According to the overall genome relatedness indices (OGRI) values, six MAGs from groundwater have been assigned to the same species as the new strain HK31-G^T. Furthermore, OGRI values between the genome of strain HK31-G^T and the genomes of its closest relatives are below the species delineation threshold. Therefore, given the polyphasic approach used, strain HK31-G^T represents a novel species of the genus Phenylobacterium, for which the name Phenylobacterium ferrooxidans sp. nov. is proposed. The type strain is HK31-G^T (DSM 116432^T = UBOCC-M-3429^T = LMG 33376^T).