Description of Erythrobacter epiphyticus sp. nov. and Sphingomonas epibiotica sp. nov., epibiotic bacteria isolated from the roots of aquatic plants.

A polyphasic taxonomic study was carried out on two bacteria isolated from the roots of aquatic plants, designated as strains T5W1-RT and T9W2T. Both are Gram-negative, rod-shaped, non-motile and aerobic bacteria. Strain T5W1-RT is red-pigmented and produces bacteriochlorophyll, while strain T9W2T is yellow and does not produce bacteriochlorophyll. Nearly complete 16S rRNA gene sequence homology related T5W1-RT to Erythrobacter, with 99.0 and 98.9% similarity to Erythrobacter dokdonensis DSM 17193T and Erythrobacter fulvus KACC 22865T, respectively, and T9W2T to Sphingomonas, with 99.2 and 99.0% similarity to Sphingomonas hankookensis KCTC 22579T and Sphingomonas lacusdianchii KCTC 72813T, respectively. DNA G+C content for T5W1-RT and T9W2T was 63.5 and 65.5 mol%, respectively. Average nucleotide identity and digital DNA-DNA hybridization with the closest phylogenetic neighbours of each isolate showed differences at the species level, further confirmed by differences in several physiological characteristics. The predominant fatty acids for T5W1-RT were C18:1 ω7c, C17:1 ω6c and C16:0, while T9W2T contained C18:1 ω7c, C16:0, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) and C14:0 2-OH. Both strains had ubiquinone 10 as the primary ubiquinone and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine and sphingoglycolipid as the dominant polar lipids. Based on the results obtained, these bacteria are new species with T5W1-RT assigned to the genus Erythrobacter with the name Erythrobacter epiphyticus sp. nov., type strain T5W1-RT (=NRRL B-65716T=DSM 118060T), and T9W2T assigned to the genus Sphingomonas with the name Sphingomonas epibiotica sp. nov., type strain T9W2T (=NRRL B-65717T=DSM 118105T).