Zobellella denitrificans gen. nov., sp nov and Zobellella taiwanensis sp nov., denitrifying bacteria capable of fermentative metabolism

Two denitrifying strains of heterotrophic, facultatively anaerobic bacteria, designated ZD1(T) and ZT1(T), were isolated from sediment samples collected from mangrove ecosystems in Taiwan. The isolates were Gram-negative. Cells grown in broth cultures were straight rods that were motile by means of a single polar flagellum. The isolates grew optimally in 1-3 % NaCl, but NaCl was not an absolute requirement for growth; only strain ZT1(T) grew in 13-14% NaCl. Both isolates grew between 10 and 45 degrees C, with optimum growth at 30-35 degrees C. They were capable of anaerobic growth by clenitrifying metabolism using nitrate or nitrous oxide as terminal electron acceptors or, alternatively, by fermenting glucose, sucrose or mannitol as substrates. C-18:1 omega 7c was the most abundant fatty acid (32(.)6-35(.)7 %). The other major fatty acids included C-16:1 omega 7c (2 7.5-29-4 %) and C-16:0 (20(.)1-22(.)0 %). The two isolates had 16S rRNA gene sequence similarity of 96(.)8 % and shared 94(.)1-96(.)8 % sequence similarity with the most closely related species, Oceanimonas doudoroffii, Oceanimonas baumannii, Oceanimonas smirnovii and Oceanisphaera litoralis. They could be distinguished from these species in that they were capable of fermentative metabolism, had relatively high DNA G + C contents (62-0-64.0 mol%) and contained C-18:1 omega 7c instead of C-16:1 omega 7c as the most abundant fatty acid. Characterization data accumulated in this study revealed that the two clenitrifying isolates could be classified as representatives of two novel species in a new genus, Zobellella gen. nov., with Zobellella denitrificans sp. nov. (type strain ZID1(T) =BCRC 17493(T)=JCM 13380(T)) as the type species and Zobellella taiwanensis sp. nov. (type strain ZT1(T) =BCRC 17494(T)=JCM 13381(T)) as a second species.