Novosphingobium acidiphilum sp nov., an acidophilic salt-sensitive bacterium isolated from the humic acid-rich Lake Grosse Fuchskuhle

A yellow- to orange-pigmented, Gram-negative, rod-shaped, motile and non-spore-forming bacterium, strain FSW06-204d(T), was isolated from subsurface water of the acidic bog lake, Lake Grosse Fuchskuhle (Brandenburg, Germany). Optimum growth of this strain occurred over a pH range from 5.5 to 6.0 and the growth rate strongly decreased at pH values above 6.5. In addition, the strain exhibited a low tolerance towards NaCl and grew only at a NaCl concentration of up to 0.5%.16S rRNA gene sequence analysis of strain FSW06-204dT showed the highest sequence similarity to Novosphingobium hassiacum W-51(T) (96.7%) and formed a distinct cluster with Novosphingobium nitrogenifigens DSM 19370(T) (96.4%) within the genus Novosphingobium. Strain FSW06-204d(T) shared a 21 bp signature gap with the latter species, a feature that is absent in all other members of the family Sphingomonadaceae. DNA-DNA hybridization of strain FSW06-204d(T) and N. nitrogenifigens DSM 19370(T) showed a low relatedness value of 24% (reciprocal: 39%). The major respiratory quinone was ubiquinone Q-10 (91%) and the predominant fatty acid was C-18:1 omega 7c (43.3%). Two characteristic 2-hydroxy fatty acids, C-14:0 2-OH (8.1%) and C-15:0 2-OH (6.5%), were abundant. Polar lipids consisted mainly of phosphatidyldimethylethanolamine and phosphatidylethanolamine; however, only moderate amounts of sphingoglycolipids were present and phosphatidylcholine was lacking. Characterization by 16S rRNA gene sequence, physiological features, pigment analysis and polyamine, ubiquinone, polar lipid and fatty acid contents revealed that strain FSW06-204d(T) represents a novel species of the genus Novosphingobium within the class Alphaproteobacteria. The name Novosphingobium acidiphilum sp. nov. is proposed for this acidophilic and salt-sensitive species with the type strain FSW06-204d(T) (=DSM 19966(T)= CCM 7496(T)= CCUG 55538(T)).