Sphingomonas lacus sp. nov., an astaxanthin-dideoxyglycoside-producing species isolated from soil near a pond

Taxonomic studies were performed on an astaxanthin-dideoxyglycoside-producing strain, designated PB304(T), isolated from soil near a pond in Daejeon city, South Korea. Cells of strain PB304(T) were Gram-staining-negative, strictly aerobic, orange-coloured and motile, and occurred as single or paired short chains. PB304(T) did not contain bacteriochlorophyll a. 16S rRNA gene sequence analysis revealed that strain PB304(T) was closely related to 'Sphingomonas humi' KCTC 12341 (98.7%), Sphingomonas kaistensis KCTC 12344(T)(97.9%), Sphingomonas astaxanthinifaciens DSM 22298(T) (97.6%) and Sphingomonas ginsengisoli KCTC 12630(T) (97.5%). Analysis of pufLM gene sequences revealed strain PB304(T) to be closely related to 'S. humi' KCTC 12341 (88.1%). The major cellular fatty acids were C16 : 0, summed feature 4 (comprising iso-C15 : 0 2-OH and/or C16 : 1ω7c), and summed feature 7 (comprising C18  : 1ω7c/ω9t/ω12t). Ubiquinone 10 (Q-10) was the sole quinone identified, and the major pigment was astaxanthin dideoxyglycoside. The major polar lipids were sphingoglycolipid, phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine. The polyamine was spermidine. The DNA-DNA relatedness values of strain PB304(T) with respect to its closest phylogenetic neighbours were 57.1% for 'S. humi' KCTC 12341, 51.2% for Sphingomonas kaistensis KCTC 12334T, 50.6% for Sphingomonas astaxanthinifaciens DSM 22298(T) and 50.2% for Sphingomonas ginsengisoli KCTC 12630(T). The DNA G+C content of strain PB304(T) was 66.6 mol%. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, strain PB304T is concluded to represent a novel species of the genus Sphingomonas, for which the name Sphingomonas lacus is proposed. The type strain is PB304(T) ( = KCTC 32458(T) = CECT 8383(T)).