Physiological and Genomic Characteristics of Duganella fontis sp. nov., Isolated from the Bottom Sediments of Buksykhen-Serdechnyi Cold Spring, Buryatia

Abstract— A chemoheterotrophic, catalase- and oxidase-positive bacterial strain BuS-21T was isolated from the bottom sediments of the Buksykhen-Serdechnyi stream in the Northern Baikal region, Buryatia. The cells were non-spore-forming, motile rods 0.5–0.8 µm thick and 1.6–1.9 µm long with a gram-negative cell wall type. The strain grew at temperatures of 5–35°C (optimum 29°C), pH 5–9 (optimum 6–8), and up to 0.5% NaCl. Preferred substrates included sugars, starch, pectin, peptone, casein, yeast extract, some organic acids, and amino acids. Ubiquinone Q-8 was the only quinone in the new bacterium. The cell envelope fatty acids of strain BuS-21T were dominated by C16:0 (41.8%) and C16:1ω7 (46.6%). Phosphatidylglycerol and phosphatidylethanolamine were the polar lipids of the isolate. The highest similarity of the complete 16S rRNA gene sequence of strain BuS-21T was observed with the species Duganella violaceipulchra HSC-15S17T (98.3%) and D. dendranthematis AF9R3T (98.2%). The complete genome of strain BuS-21T was represented by a circular chromosome of approximately 6.5 Mb in size, containing 5774 genes with an average G + C pair content of 63% and encoding 5574 proteins. DNA-DNA hybridization (dDDH) and nucleotide sequence similarity (ANI) between strain BuS-21T and the closely related species D. radicis Sac-41T were 31.3 and 86.41%, respectively. Based on its phenotypic, physiological, and biochemical properties and phylogenomic analysis, we propose classifying the isolated bacterium as a member of a new species of the genus Duganella, D. fontis sp. nov. Strain BuS-21T (=VKM B-3064T=JCM 32511T) is the type strain of the new species.