Prosthecate sphingomonads: proposal of Sphingomonas canadensis sp. nov

Two stalked, aerobic, catalase- and oxidase-positive rod-shaped isolates, VKM B-1508 ( = CB 258) and FWC47T, were analysed using a polyphasic approach. While the morphology and the 16S rRNA gene sequence of strain VKM B-1508 were 100 % identical to the ones of Sphingomonas leidyi DSM 4733T, the morphology of FWC47T was different, and the closest recognized species were Sphingomonas oligophenolica S213T ( = DSM 17107T) and Sphingomonas leidyi DSM 4733T with 97.2 % and 97.0 % 16S rRNA gene sequence similarity, respectively. DNA–DNA hybridization studies supported the differentiation of strain FWC47T from S. oligophenolica and S. leidyi. Strain FWC47T grew optimally at 28–30 °C, and pH 6.0–8.0. The major respiratory quinone was Q10 and the major polyamine was sym-homospermidine. The major fatty acids were C17 : 1ω6c and C18 : 1ω7c and C15 : 0 2-OH was the major 2-hydroxy fatty acid. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidyldimethylethylamine and unidentified sphingoglycolipids. The G+C content of the genomic DNA of strain FWC47T was 67.1 mol%. Strain FWC47T differed from S. leidyi by its ability to assimilate l-alanine, maltose and sucrose, by the presence of β-galactosidase and α-chymotrypsin, and the lack of valine arylamidase and β-glucosidase activities. Contrary to S. leidyi, FWC47T did not reduce nitrate and could not use fructose, acetate and N-acetyl-glusosamine. In the genus Sphingomonas, the dimorphic life cycle involving a prosthecate sessile and a flagellated swarmer cell was hitherto only known from Sphingomonas leidyi. Therefore, strain FWC47T represents an additional distinct prosthecate species in this genus for which the name Sphingomonas canadensis is proposed. The type strain is FWC47T ( = LMG 27141T = CCUG 62982T).