Genome-based classification of genera Halosegnis and Salella, and description of four novel halophilic archaea isolated from a tidal flat.

Abstract

The current species of Halosegnis and Salella within the class Halobacteria are closely related based on phylogenetic, phylogenomic, and comparative genomic analyses. The Halosegnis species showed 99.8-100.0% 16S rRNA and 96.6-99.6% rpoB' gene similarities to the Salella species, respectively. Phylogenetic and phylogenomic analyses showed that Salella cibi CBA1133^T, the sole species of Salella, formed a single tight cluster with Halosegnis longus F12-1^T, then with Halosegnis rubeus F17-44^T. The average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and average amino acid identity (AAI) values between Salella cibi CBA1133^T and Halosegnis longus F12-1^T were 99.2, 94.2, and 98.6%, respectively, much higher than the thresholds for species demarcation. This genome-based classification revealed that the genus Salella should be merged with Halosegnis, and Salella cibi should be a later heterotypic synonym of Halosegnis longus. Halophilic archaeal strains DT72^T, DT80^T, DT85^T, and DT116^T, isolated from the saline soil of a tidal flat in China, were subjected to polyphasic taxonomic characterization. The phenotypic, chemotaxonomic, phylogenetic, and phylogenomic features indicated that strains DT72^T (= CGMCC 1.18925^T = JCM 35418^T), DT80^T (= CGMCC 1.18926^T = JCM 35419^T), DT85^T (= CGMCC 1.19049^T = JCM 35605^T), and DT116^T (= CGMCC 1.19045^T = JCM 35606^T) represent four novel species of the genera Halorussus, Halosegnis and Haloglomus, respectively, for which the names, Halorussus caseinilyticus sp. nov., Halorussus lipolyticus sp. nov., Halosegnis marinus sp. nov., and Haloglomus litoreum sp. nov., are proposed.