Acidisoma cladoniae sp. nov., an acidotolerant bacterium isolated from an Antarctic lichen

Gram-staining-negative, aerobic, white-cream-pearly colony, coccobacilli, and non-motile bacterial strain, PAMC 29798^T was isolated from an Antarctic lichen. The strain was acidotolerant and psychrotolerant growing at pH 4.0-7.5 (optimally at pH 4.0-6.5) and 0-25 °C (optimally at 10-20 °C). The major fatty acids are Summed Feature 8, C_18:1 2OH, and C_19:0 cyclo ω8c. The major respiratory quinone was Q-10. Phylogenetic and phylogenomic analyses indicated that strain PAMC 29798^T belonged to the genus Acidisoma and 16S rRNA gene sequences of PAMC 29798^T were closely related to Acidisoma silvae (97.7% sequence similarity), Acidisoma cellulosilyticum (96.5%), Acidisoma tundrae (96.5%), and Acidisoma sibiricum (96.3%). Genomic relatedness analyses showed that strain PAMC 29798^T was clearly distinguished from type strains of the genus Acidisoma based on values of average nucleotide identity (< 75%) and the digital DNA-DNA hybridization (< 19.6%). Genome analysis revealed that the genome size of PAMC 29798^T is approximately 5.0 Mb with a G+C content of 63.4%. The complete genome comprises 5 contigs containing 4636 protein-coding genes, 46 tRNA genes, and 2 rRNA operons. The genome possesses genes for light-harvesting complexes, type-II photosynthetic reaction center, and C-P lyase to solubilize organic phosphates, while genes encoding nitrogenase iron protein involved in the nitrogen fixation were not present. Based on the results of phylogenetic, genome-based relatedness, and physiological and genomic analyses, strain PAMC 29798^T is proposed to represent a novel species of the genus Acidisoma, with the name Acidisoma cladoniae. The type strain is PAMC 29798^T (= KCTC 82159^T = JCM 35634^T).