Cyclobacterium salsum sp. nov. and Cyclobacterium roseum sp. nov., isolated from a saline lake.

Two novel strains, designated SYSU L10167T and SYSU L10180T, were isolated from sediment sampled at Dabancheng saline lake in Xinjiang, PR China. A polyphasic approach was used to clarify the taxonomic positions of the two strains. Cells of the isolates were curved ring-like, horseshoe-shaped or rod-shaped, non-motile and non-spore-forming. Cells were Gram-stain-negative, aerobic, heterotrophic and rose-pigmented. The phylogenetic trees based on 16S rRNA gene sequences showed that strains SYSU L10167T and SYSU L10180T formed a distinct lineage within the genus Cyclobacterium. Strains SYSU L10167T and SYSU L10180T showed highest similarities to Cyclobacterium jeungdonense KCTC 23150T (98.0 and 97.4%, respectively). Results of genomic analyses (including average nucleotide identity, digital DNA-DNA hybridization and the marker gene tree) and pan-genome analysis further confirmed that strains SYSU L10167T and SYSU L10180T were separate from each other and other species of the genus Cyclobacterium. The draft genomes of the isolates had sizes of 5.5-5.7 Mb and reflected their major physiological capabilities. Based on phenotypic, physiological, chemotaxonomic and genotypic characterization, we propose that the isolates represent two novel species, for which the names Cyclobacterium salsum sp. nov. and Cyclobacterium roseum sp. nov. are proposed. The type strains of the species are SYSU L10167T (=KCTC 72390T=CGMCC 1.17521T) and SYSU L10180T (=KCTC 72391T=CGMCC 1.17278T).

Taxogenomics of the Genus Cyclobacterium: Cyclobacterium xiamenense and Cyclobacterium halophilum as Synonyms and Description of Cyclobacterium plantarum sp. nov.

The genus Cyclobacterium belongs to the phylum Bacteroidetes and includes eight species. Our study, based on the genomic parameters in silico DNA-DNA hybridization (GGDC), average nucleotide identity (OrthoANI), and average amino acid identity (AAI), confirmed that all current species of Cyclobacterium belong to this genus and constitute a coherent phylogenomic group, but with species forming two separate branches. In addition, the genome-based analyses revealed that Cyclobacterium xiamenense and Cyclobacterium halophilum are members of the same species. Besides, we carried out a taxonomic characterization of the new strain GBPx2T, isolated from the halophytic plant Salicornia sp. Analysis of its 16S rRNA gene sequence showed the highest sequence similarity (97.5%) to Cyclobacterium lianum HY9T. Percentages of GGDC and OrthoANI between strain GBPx2T and species of the genus Cyclobacterium were lower than the threshold value for species delineation. The DNA G+C content was 43.0 mol%. The polar lipids included phosphatidylethanolamine as well as one unidentified phospholipid and four unidentified lipids, and its major cellular fatty acids were iso-C15:0 and summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH). The only quinone present was menaquinone 7. Based on a combination of phenotypic, chemotaxonomic, and phylogenomic features, the GBPx2T strain represents a novel species of the genus Cyclobacterium, for which the name Cyclobacterium plantarum sp. nov. is proposed. The type strain of Cyclobacterium plantarum is GBPx2T (= IBRC-M 10634T = LMG 28551T).

Cyclobacterium sediminis sp. nov. isolated from a sea cucumber aquaculture farm and emended description of the genus Cyclobacterium.

An aerobic, Gram-negative bacterium, designated strain SD70T, was isolated from sea cucumber aquaculture farm sediment in Taean, Korea, and its taxonomic status was established by undertaking a polyphasic study. Cells of strain SD70T were non-motile, catalase-, and oxidase-positive, non-spore-forming, and horseshoe-shaped. Optimal growth was observed under 25-30°C, pH 7.0-8.0, and 3.0-5.0% (w/v) NaCl conditions. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain SD70T fell within an evolutionary group comprising species of the genus Cyclobacterium. Strain SD70T shared 92.1-98.5% 16S rRNA sequence similarity values with the type strains of species of the genus Cyclobacterium. Relatively low levels of DNA-DNA relatedness were found between strain SD70T and C. marinum DSM 745T (40.2%) and C. amurskyense KMM 6143T (15.8%). The predominant cellular fatty acids were iso-C15:0 (32.1%), and anteiso-C15:0 (9.1%). Menaquinone MK-7 was the only respiratory quinone. The G+C content of the genomic DNA was 36 mol%. The polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and seven unidentified lipids. On the basis of phenotypic and genotypic data, strain SD70T represents a novel species of the genus Cyclobacterium, for which the name Cyclobacterium sediminis sp. nov. is proposed. An emended description of the genus Cyclobacterium is also provided.