Two white colony-forming, Gram-stain-negative, non-sporulating and motile bacteria, designated G-4-1-8T and RP-4-7T, were isolated from forest soil and Arctic soil, respectively. Both strains showed antimicrobial activity against Gram-negative pathogens (Pseudomonas aeruginosa and Escherichia coli) and could grow at a pH range of pH 4.0-11.0 (optimum, pH 7.0-9.0). Phylogenetic analyses based on their 16S rRNA gene sequences indicated that strains G-4-1-8T and RP-4-7T formed a lineage within the family Burkholderiaceae and were clustered as members of the genus Paraburkholderia. Strain G-4-1-8T showed the highest 16S rRNA sequence similarity to Paraburkholderia monticola JC2948T (98.1 %), while strain RP-4-7T showed the highest similarity to Paraburkholderia metrosideri DNBP6-1T (98.8 %). The only respiratory quinone in both strains was ubiquinone Q-8. Their principal cellular fatty acids were C16 : 0, cyclo-C17 : 0, summed feature 3 (iso-C15 :0 2-OH and/or C16 :1 ω7c) and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). Their major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and an unidentified aminophospholipid. The DNA G+C content of strains G-4-1-8T and RP-4-7T were 63.7 and 61.3 mol%, respectively, while their genome lengths were 7.44 and 9.67 Mb, respectively. The genomes of both strains showed at least 12 putative biosynthetic gene clusters. The average nucleotide identity and in silico DNA-DNA hybridization relatedness values between both strains and most closely related Paraburkholderia species were below the species threshold values. Based on a polyphasic study, these isolated strains represent novel species belonging to the genus Paraburkholderia, for which the names Paraburkholderia antibiotica sp. nov. (G-4-1-8T= KACC 21617T=NBRC 114603T) and Paraburkholderia polaris sp. nov. (RP-4-7T=KACC 21621T=NBRC 114605T) are proposed.
Keywords: Arctic soil; antimicrobial agents; antimicrobial resistance; forest soil; psychrotolerant.