Sphingomonas phyllosphaerae sp. nov., from the phyllosphere of Acacia caven in Argentina.

Two bacterial strains (FA1 and FA2(T)) were isolated from the phyllosphere of a leguminous tree, Acacia caven, in central Argentina. The strains were Gram-negative, strictly aerobic, rod-shaped, motile and formed yellow-pigmented colonies on nutrient agar. The two-primer RAPD patterns of the two strains were identical, suggesting that they belong to the same species. The complete 16S rRNA gene sequences of the two strains were obtained and comparisons demonstrated that they cluster phylogenetically with the species of the genus Sphingomonas sensu stricto. Strain FA2(T) was most closely related (97.6 %) to Sphingomonas adhaesiva. 16S rRNA gene sequence similarities to all other established Sphingomonas species ranged from 94.4 % (to Sphingomonas echinoides) to 97.6 % (to S. adhaesiva). Strains FA1 and FA2(T) were catalase-positive and oxidase-negative. Aesculin was hydrolysed, gelatin and urea were not. beta-Galactosidase was produced. From 51 compounds tested 21 were used as single sources of carbon. The major respiratory lipoquinone was ubiquinone-10. The predominant cellular fatty acids were 16 : 0, 18 : 1omega7c and 16 : 1omega7c (from summed feature 3). Hydroxy fatty acids 14 : 0 2-OH and 15 : 0 iso 2-OH were present as well (from summed feature 4). The polar lipids detected in strain FA2(T) were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid and two unidentified phospholipids. The DNA G+C content of strain FA2(T) was 61 mol%. DNA-DNA hybridization experiments showed 27.6 % relatedness between strain FA2(T) and S. adhaesiva DSM 7418(T). Based upon phenotypic and molecular evidence, a novel species of the genus Sphingomonas is proposed, Sphingomonas phyllosphaerae sp. nov., with strain FA2(T) (=LMG 21958(T)=CECT 5832(T)) as the type strain.