Roseithermus sacchariphilus gen. nov., sp. nov. and proposal of Salisaetaceae fam. nov., representing new family in the order Rhodothermales

Abstract

A novel bacterium with cells that were pinkish-cream-coloured, aerobic, rod-shaped, 0.62–1.00 µm wide and 2.3–3.3 µm long, designated as strain MEBiC09517T, was isolated from Buksung-Po, a small port in Incheon, Republic of Korea. Strain MEBiC09517T had low 16S rRNA gene sequence similarity to validly reported strains; among them, Rubrivirga profundi SAORIC-476T displayed highest sequence similarity (89.9 %). Nevertheless, the novel strain shared a phylogenetic line with members of the genus Rhodothermus , not the genus Rubrivirga . Optimum growth conditions of strain MEBiC09517T were at 50–55 °C, pH 7 and in 2.0–4.0 % salt concentration. Strain MEBiC09517T was found to be an obligate marine bacterium that requires KCl, MgCl2 and CaCl2 as well as NaCl for growth. A phosphatidylethanolamine, a diphosphatidylglycerol, three glycolipids and four unidentified lipids were the strain's predominant polar lipid components. The fatty acid of the cell wall mainly consisted of carbons with 16 or 18 chain lengths such as C16 : 0, C18 : 0, C18 : 1 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c). The predominant menaquinone was MK-7. The DNA G+C content is 68.65 mol%. Strain MEBiC09517T differs from genera of the order Rhodothermales in terms of fatty acid composition, growth conditions, and range of carbon source utilization. Based on phylogenetic analysis using the strain's 16S rRNA gene sequence and results of physiological tests, strain MEBiC09517T (KCCM=43267T, JCM=32374T) is proposed as Roseithermus sacchariphilus gen. nov., sp. nov. Additionally, the novel family Salisaetaceae fam. nov. based on phylogenetic analysis and physiological characteristics is suggested.