Pseudarthrobacter raffinosi sp. nov. and Pseudarthrobacter cellobiosi sp. nov. Two Heavy-Metal-Tolerant and Psychrotolerant Bacteria Isolated from Glaciers.

In a study on bacterial diversity on glacier surfaces in China, five bacterial strains (HLT1-5, HLT3-5, MDT3-26, MDT3-9, and MDT3-28) were isolated from soil samples collected from the surfaces of Hailuogou glacier and Midui glacier. Phylogenetic analysis based on 16S rRNA gene sequences placed these strains close to Pseudarthrobacter humi RMG13, Pseudarthrobacter psychrotolerans YJ56, and Pseudarthrobacter sulfonivorans ALL, with sequence similarity ranging from 98.98 to 100%. The phylogenomic tree further confirmed these relationships. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between these five strains and other members of the genus Pseudarthrobacter were both lower than 95% and 70%, respectively, indicating that they represent two novel species. The draft genomes contained 4162-4359 genes, including several resistance genes for heavy metals. They exhibited varying levels of resistance to heavy metals such as Cu⁺, Co⁺, and Zn⁺. Genomic data indicated that the strains harbored copper-exporting ATPase genes, multi-copper oxidases, and other key genes related to copper, cobalt, zinc, and cadmium resistance. Based on polyphasic characterizations, strains MDT3-26, MDT3-28, and MDT3-9 represent a novel species of the genus Pseudarthrobacter, for which the name Pseudarthrobacter raffinosi sp. nov. is proposed, with the type strain MDT3-26 (= CGMCC 1.9918 = NBRC 113090). Strains HLT1-5 and HLT3-5 represent another novel species, for which the name Pseudarthrobacter cellobiosi sp. nov. is proposed, with the type strain HLT1-5 (= CGMCC 1.9998 = NBRC 113091). These findings characterize two novel species within the genus Pseudarthrobacter and provide new insights into the bioremediation potential of this genus.