Prosthecate sphingomonads: proposal of Sphingomonas canadensis sp nov.

Two stalked, aerobic, catalase- and oxidase-positive rod-shaped isolates, VKM B-1508 (=CB 258) and FWC47(T), 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 4733(T), the morphology of FWC47(T) was different, and the closest recognized species were Sphingomonas oligophenolica S213(T) (=DSM 17107(T)) and Sphingomonas leidyi DSM 4733(T) with 97.2% and 97.0% 16S rRNA gene sequence similarity, respectively. DNA-DNA hybridization studies supported the differentiation of strain FWC47(T) from S. oligophenolica and S. leidyi. Strain FWC47(T) grew optimally at 28-30 degrees 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 C-17:1 omega 6c and C-18:1 omega 7c and C-15:0 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 FWC47(T) was 67.1 mol%. Strain FWC47(T) differed from S. leidyi by its ability to assimilate L-alanine, maltose and sucrose, by the presence of beta-galactosidase and alpha-chymotrypsin, and the lack of valine arylamidase and beta-glucosidase activities. Contrary to S. leidyi, FWC47(T) 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 FWC47(T) represents an additional distinct prosthecate species in this genus for which the name Sphingomonas canadensis is proposed. The type strain is FWC47(T) (=LMG 27141(T)=CCUG 62982(T)).