Zobellella iuensis sp. nov., an aerobic denitrifying bacterium isolated from activated sludge

An aerobic denitrifying bacterium, designated as strain CPY4^T, was isolated from activated sludge treating urban sewage under alternating aerobic/anaerobic conditions by an enrichment culture technique. Cells of strain CPY4^T were Gram-stain-negative, aerobic, long rod-shaped, motile by means of single polar flagellum and capable of aerobic denitrification with citrate as the carbon source. Growth of strain CPY4^T was observed at 10-45 °C (optimum, 30-35 °C), at pH 6.0-10.5 (optimum, pH 8.0-8.5) and in 0-5 % NaCl (optimum, 0-3 %; w/v). The 16S rRNA gene sequence of strain CPY4^T showed the highest similarity to Zobellella denitrificans ZD1^T (97.9 %), followed by Zobellella endophytica 59N8^T (97.6 %), Zobellella aerophila JC2671^T (97.2 %), Zobellella taiwanensis ZT1^T (97.1 %) and Zobellella maritima 102-Py4^T (96.3 %). Genome comparisons between CPY4^T and other Zobellella species showed highest digital DNA-DNA hybridization with Z. denitrificans ZD1^T (43.8 %) and highest average nucleotide identity (ANIb and ANIm) of genome nucleotide sequences with Z. denitrificans ZD1^T(90.7 and 92 %, respectively). Phylogenetic analysis revealed that strain CPY4^T fell within the clade comprising the type strains of Zobellella species and formed a phyletic line with them, which was distinct from other members of the family Aeromonadaceae. The sole respiratory ubiquinone was quinone 8. The predominant fatty acids (>10 % of the total fatty acids) of strain CPY4^T were summed feature 8 (C_18 : 1  ω6c and/or C_18 : 1  ω7c), summed feature 3 (C_16 : 1  ω6c and/or C_16 : 1  ω7c) and C_16 : 0. The genomic DNA G+C content was 62.7 mol %. In the polar lipid profile, diphosphatidylglycerol, phosphatidylglycerol, phosphatidyl ethanolamine, phospholipids and aminolipids were the major compounds. Based on the genotypic and phenotypic data, strain CPY4^T represents a novel species of the genus Zobellella, for which the name Zobellella iuensis sp. nov. is proposed. The type strain is CPY4^T (=JCM 34456^T=CGMCC 1.18722^T).