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

A novel bacterial strain, HK31-GT, 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-GT is a mesophilic bacterium able to grow from 10 to 30 degrees 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 degrees C and pH 6. Strain HK31-GT is chemoorganoheterotroph and its major saturated fatty acids are C18:1 omega 7c, C16:1 omega 6c 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-GT 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-GT. Furthermore, OGRI values between the genome of strain HK31-GT and the genomes of its closest relatives are below the species delineation threshold. Therefore, given the polyphasic approach used, strain HK31-GT represents a novel species of the genus Phenylobacterium, for which the name Phenylobacterium ferrooxidans sp. nov. is proposed. The type strain is HK31GT (DSM 116432T = UBOCC-M-3429T = LMG 33376T).