Alteromonas tagae sp. nov. and Alteromonas simiduii sp. nov., mercury-resistant bacteria isolated from a Taiwanese estuary

Abstract

Two mercury-resistant strains of heterotrophic, aerobic, marine bacteria, designated AT1T and AS1T, were isolated from water samples collected from the Er-Jen River estuary, Tainan, Taiwan. Cells were Gram-negative rods that were motile by means of a single polar flagellum. Buds and prosthecae were produced. The two isolates required NaCl for growth and grew optimally at about 30 °C, 2–4 % NaCl and pH 7–8. They grew aerobically and were incapable of anaerobic growth by fermenting glucose or other carbohydrates. They grew and expressed Hg2+-reducing activity in liquid media containing HgCl2. Strain AS1T reduced nitrate to nitrite. The predominant isoprenoid quinone was Q8 (91.3–99.9 %). The polar lipids of strain AT1T consisted of phosphatidylethanolamine (46.6 %), phosphatidylglycerol (28.9 %) and sulfolipid (24.5 %), whereas those of AS1T comprised phosphatidylethanolamine (48.2 %) and phosphatidylglycerol (51.8 %). The two isolates contained C16 : 1 ω7c and/or iso-C15 : 0 2-OH (22.4–33.7 %), C16 : 0 (19.0–22.7 %) and C18 : 1 ω7c (11.3–11.7 %) as the major fatty acids. Strains AT1T and AS1T had DNA G+C contents of 43.1 and 45.3 mol%, respectively. Phylogeny based on 16S rRNA gene sequences, together with data from morphological, physiological and chemotaxonomic characterization, indicated that the two isolates could be classified as representatives of two novel species in the genus Alteromonas, for which the names Alteromonas tagae sp. nov. (type strain AT1T=BCRC 17571T=JCM 13895T) and Alteromonas simiduii sp. nov. (type strain AS1T=BCRC 17572T=JCM 13896T) are proposed.