Two floc-forming, nitrogen-fixing bacteria, strains EMB43 and EMB61, obtained from activated sludge of a domestic wastewater treatment plant in Korea, were characterized. The two strains were very closely related, sharing 99.7 % 16S rRNA gene sequence similarity and showing a level of DNA–DNA relatedness of 93 %, which suggests that they represent members of a single species. Phylogenetic analysis based on 16S rRNA gene sequences showed that the two novel isolates formed a distinct phyletic lineage within the genus and were related most closely to DhA-35 and A-7, with sequence similarities of 97.2 %. Levels of DNA–DNA relatedness between strain EMB43 and DhA-35 and A-7 were 12.8 and 7.4 %, respectively. Cells of strains EMB43 and EMB61 were facultatively aerobic, rod-shaped, Gram-negative and motile by means of a polar flagellum. The strains grew at temperatures of 15–40 °C (optimum: 25–30 °C) and at pH 6.0–9.0 (optimum: pH 6.5–7.5). The predominant fatty acids were C, C 3-OH and summed feature 3 (C 7 and/or iso-C 2-OH), and the predominant polar lipid was phosphatidylethanolamine. The genomic DNA G+C content was 64.9–65.0 mol% and the major isoprenoid quinone was ubiquinone-8 (Q-8). On the basis of phenotypic, chemotaxonomic and molecular data, the isolates are considered to represent a novel species of the genus , for which the name sp. nov. is proposed. The type strain is EMB43 (=KCTC 22084=DSM 19389).


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Cellular fatty acid compositions of strains EMB43 and EMB61 and related species [ PDF] (46 KB)


Transmission electron micrograph showing general morphology of negatively stained cells of strain EMB43 after growth for 3 days at 30 °C on R2A agar. Bar, 1 µm.

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