Sphingomonas longa sp. nov., Sphingomonas mollis sp. nov. and Sphingomonas aurea sp. nov.: three novel Sphingomonas species isolated from soil.

Abstract

Three Gram-negative, aerobic and non-motile bacterial strains, BT552^T, BT553^T and KR1UV-12^T, were isolated from soil samples in Gwangju-si and Gangneung-si, the Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequence showed that strains BT552^T, BT553^T and KR1UV-12^T clustered to a distinct clade within the family Sphingomonadaceae (order Sphingomonadales, class Alphaproteobacteria). The strains exhibited the highest genetic similarity with representatives of the genus Sphingomonas; moreover, strains BT552^T and BT553^T tightly clustered with Sphingomonas melonis DAPP-PG 224^T (98.2 and 98.1 %) and Sphingomonas aquatilis JSS-7^T (98.1 and 98.0 %), while strain KR1UV-12^T clustered with S. melonis DAPP-PG 224^T (97.9%) and Sphingomonas rubra BH3^T (97.8%), respectively. The major cellular fatty acids of all three strains were summed feature 8 (C_18:1 ω7c/C_18:1 ω6c), comprising 44.7, 46.4 and 48.5%. Additionally, their respiratory quinone is Q-10, and polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phospholipids, sphingolipid and phosphatidylcholine. They all grow well at an optimum temperature of 25 °C, at pH 7. The draft genomes of strains BT552^T, BT553^T and KR1UV-12^T measures 4 035 561 bp, 3 941 714 bp and 3 418 792 bp, respectively, comprising 3 804 3648 and 3236 coding sequences and 50, 48 and 45 RNA genes. The average nucleotide identity analysis and digital DNA-DNA hybridization values between BT552^T, BT553^T and KR1UV-12^T and closely related Sphingomonas species range from 72.7 to 80.2% and 19.4 to 24.3%, respectively. Based on phenotypic, genotypic and chemotaxonomic data, these three strains BT552^T, BT553^T and KR1UV-12^T represent three novel bacterial species within the genus Sphingomonas for which the names Sphingomonas longa sp. nov. (type strain BT552^T= KCTC 82094^T =NBRC 114993^T), Sphingomonas mollis sp. nov. (type strain BT553^T =KCTC 82095^T =NBRC 114994^T) and Sphingomonas aurea sp. nov. (type strain KR1UV-12^T = KCTC 92959^T = TBRC 18506^T) are proposed.