Gemmobacter denitrificans sp. nov., a denitrifying bacterium, isolated from pond water for Litopenaeus vannamei

A novel Gram-stain-negative strain, designated JM10B15^T, was isolated from pond water for Litopenaeus vannamei collected from Jiangmen City, Guangdong province, south PR China. Cells of the strain were aerobic, rod-shaped, and motile by lateral flagella. JM10B15^T could grow at 15-40 °C, pH 6.0-9.5, and in 0-3.0 % NaCl, with optimal growth at 25-35 °C, pH 7.5-8.5, and in 0 % NaCl, respectively. Furthermore, this strain grew well on Reasoner's 2A agar but not on nutrient broth agar or Luria-Bertani agar. JM10B15^T was a denitrifying bacterium capable of removing nitrites and nitrates, and three key functional genes, nasA, nirS, and nosZ, were identified in its genome. The results of phylogenetic analyses based on the 16S rRNA gene and genome sequences indicated that JM10B15^T belonged to the genus Gemmobacter. JM10B15^T showed the highest 16S rRNA sequence similarity to Gemmobacter lutimaris YJ-T1-11^T (98.8 %), followed by Gemmobacter aquatilis IFAM 1031^T (98.6 %) and Gemmobacter serpentinus HB-1^T (98.1 %). The average nucleotide identity and digital DNA-DNA hybridization values between JM10B15^T and the other type strains of genus Gemmobacter were 78.1-82.1 % and 18.4-22.1 %, respectively. The major fatty acids of strain JM10B15^T were summed feature 8 (C_18 : 1  ω6c and/or C_18 : 1  ω7c) and C_18 : 1  ω7c 11-methyl. In addition, the major respiratory quinone of this novel strain was Q-10, and the predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, four unidentified phospholipids, three unidentified lipids, and an unidentified aminophospholipid. Results of analyses of the phylogenetic, genomic, physiological, and biochemical characteristics indicated that JM10B15^T represents a novel species of the genus Gemmobacter, for which the name Gemmobacter denitrificans sp. nov. is proposed. The type strain is JM10B15^T (=GDMCC 1.4148^T=KCTC 8140^T).