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More than forty isolates of marine, facultatively anaerobic, fermentative bacteria were recovered from sediment samples collected from the lagoon of Dongsha Island, Taiwan, using an anaerobic enrichment culture method. Two of the isolates were selected for characterization and classification in the present study. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the two isolates could be placed under class Gammaproteobacteria. The phylogenetic data and those from chemotaxonomic, physiological and morphological characterizations further supported the establishment of a novel species and genus inside the family Aeromonadaceae. The name, Dongshaea marina, was proposed for this novel bacterium considering that it was recovered from a sample of marine source collected from Dongsha Island. Majority of the recognized species of marine, facultatively anaerobic, fermentative bacteria are currently placed in the family Vibrionaceae under the class Gammaproteobacteria, including the genera, Vibrio, Photobacterium, Aliivibrio, Enterovibrio, Grimontia and Salinivibrio. Vibrio is the largest genus including more than 100 species. More than ten of other marine bacteria of this kind are also located in the family Aeromonadaceae including the genera, Oceanimonas, Oceanisphaera and Zobellella. Dongshaea would be the fourth genus of Aeromonadaceae, including such kind of bacteria. Dongshaea marina exhibited significant phylogenetic distinctiveness and was distinguishable from other Aeromonadaceae species particularly in that it lacked catalase activity and produced gas during glucose fermentation. The recovering of Dongshaea marina suggests that there might still be a wide variety of novel marine bacteria remained to be unexplored in the lagoon of Dongsha Island.

This study has been published on line ahead of print by International Journal of Systematic and Evolutionary Microbiology (https://doi.org/10.1099/ijsem.0.003080). The authors include Prof. W. Y. Shieh and other contributors who have participated in this study.

Fig. 1. Sample collection in the lagoon of Dongsha Island (courtesy from Prof. C.-L. Wei).

Fig. 2. Neighbour-joining tree derived from 16S rRNA gene sequences showing the phylogenetic position of Dongshaea marina strains, DM1 and DM2^T, among members of the family Aeromonadaceae and other bacteria (taken from Fig. 1 of the paper).

Fig. 3. Electron micrographs of the broth culture of Dongshaea marina DM2^T consisting of non-flagellated (a, b) and polar-flagellated (c) cells. The cell in (b) seemed to be in multiplying-like stage. (taken from Fig. S2 of the paper).