Prosthecate sphingomonads: proposal of Sphingomonas canadensis sp. nov.

Abstract

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).