Sphingosinicella flava sp. nov., indole acetic acid producing bacteria isolated from maize field soil

A novel isolated yellow-pigmented bacterial designated strain UDD2^T was isolated from a maize field soil sample collected in Ilsan, Republic of Korea. Cells of strain UDD2^T were Gram-stain-negative, non-sporulating, long rod-shaped and exhibited flagellar motility. Cells could grow at 15-42 °C and pH 5.5-11.0. Strain UDD2^T was sensitive to NaCl and barely tolerated up to 1 % NaCl (w/v). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain UDD2^T formed a separate clade with the members of genus Sphingosinicella within the family Sphingomonadaceae. Strain UDD2^T showed the highest 16S rRNA gene sequence similarity to Sphingosinicella vermicomposti KCTC 224446^T (98.5 %) and Sphingosinicella humi KCTC 62519^T (96.7 %), followed by members of the genus Sphingomonas (96.4-94.5 %) and Sphingobium (96.1-94.9 %), but they were located in other phylogenetic clusters. Average nucleotide identity and digital DNA-DNA hybridization values between strain UDD2^T and S. vermicomposti KCTC 224446^T and S. humi KCTC 62519^T were 80.2/24.2 and 75.6/20.4 %, respectively. The total size of the genome was 2 421 697 bp and composed of one circular chromosome, with a G+C content of 63.7 mol%. Strain UDD2^T produced indole acetic acid (IAA) in the presence of l-tryptophan. Bacterial IAA is a crucial phytohormone in plant growth and development. Gene clusters for indole-3-glycerol phosphate synthase and tryptophan synthase were found in the genome of strain UDD2^T. To the best of our knowledge, no member of the genus Sphingosinicella has been reported to produce IAA to date. The major cellular fatty acids (>10 %) were found to be C_16 : 0, C_14 : 0 2OH and summed feature 3 (comprising C_{16  : 1} ω7c and/or iso-C_{15  :  0} 2-OH). Strain UDD2^T had ubiquinone Q-10 as the major respiratory quinone and homospermidine as the major polyamine. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, phosphatidylglycerol, phosphatidylcholine, three unidentified phosphoglycolipids, one unidentified phospholipid, one unidentified aminoglycophospholipid, one unidentified glycolipid and one unidentified polar lipid. Based on the phylogenetic, phenotypic, chemotaxonomic and genotypic data, strain UDD2^T represents a novel species of the genus Sphingosinicella, for which the name Sphingosinicella flava is proposed. The type strain is UDD2^T (=KCTC 82357^T=NBRC 114507^T).