A Gram-negative, aerobic, rod-shaped, non-motile, yellow-pigmented bacterium, KMM 9835^T, was isolated from the sediment sample obtained from the Amur Bay of the Sea of Japan seashore, Russia. Phylogenetic analyses based on the 16S rRNA gene and whole genome sequences positioned the novel strain KMM 9835^T in the genus Mariniflexile as a separate line sharing the highest 16S rRNA gene sequence similarities of 96.6% and 96.2% with Mariniflexile soesokkakense RSSK-9^T and Mariniflexile fucanivorans SW5^T, respectively, and similarity values of <96% to other recognized Mariniflexile species. The average nucleotide identity and digital DNA–DNA hybridization values between strain KMM 9835^T and M. soesokkakense KCTC 32427^T, Mariniflexile gromovii KCTC 12570^T, M. fucanivorans DSM 18792^T, and M. maritimum M5A1M^T were 83.0%, 82.5%, 83.4%, and 78.3% and 30.7%, 29.6%, 29.5%, and 24.4%, respectively. The genomic DNA GC content of strain KMM 9835^T was 32.5 mol%. The dominant menaquinone was MK-6, and the major fatty acids were iso-C15:0, iso-C15:1ω10c, and C15:0. The polar lipids of strain KMM 9835^T consisted of phosphatidylethanolamine, two unidentified aminolipids, an unidentified phospholipid, and six unidentified lipids. A pan-genome analysis showed that the KMM 9835^T genome encoded 753 singletons. The annotated singletons were more often related to transport protein systems (SusC), transcriptional regulators (AraC, LytTR, LacI), and enzymes (glycosylases). The KMM 9835^T genome was highly enriched in CAZyme-encoding genes, the proportion of which reached 7.3%. Moreover, the KMM 9835^T genome was characterized by a high abundance of CAZyme gene families (GH43, GH28, PL1, PL10, CE8, and CE12), indicating its potential to catabolize pectin. This may represent part of an adaptation strategy facilitating microbial consumption of plant polymeric substrates in aquatic environments near shorelines and freshwater sources. Based on the combination of phylogenetic and phenotypic characterization, the marine sediment strain KMM 9835^T (=KCTC 92792^T) represents a novel species of the genus Mariniflexile, for which the name Mariniflexile litorale sp. nov. is proposed.

Some marine and extremophilic microorganisms are capable of synthesizing sulfated polysaccharides with a unique structure. A number of studies indicate significant biological properties of individual sulfated polysaccharides, such as antiproliferative activity, which makes them a promising area for further research. In this study, the capsular polysaccharide (CPS) was obtained from the bacterium Cobetia marina KMM 1449, isolated from a marine sediment sample collected along the shore of the Sea of Japan. The CPS was isolated by saline solution, purified by a series of chromatographic procedures, and studied by chemical methods along with 1D and 2D ¹H and ¹³C NMR spectroscopy. The following new structure of the CPS from C. marina KMM 1449 was established and consisted of sulfated and simultaneously phosphorylated disaccharide repeating units: →4)-α-L-Rhap2S-(1→3)-β-D-Manp6PGro-(1→. To elucidate the genetic basis of the CPS biosynthesis, the whole genomic sequence of C. marina KMM 1449 was obtained. The CPS biosynthetic gene cluster (BGC) of about 70 genes composes four regions encoding nucleotide sugar biosynthesis (dTDP-Rha and GDP-Man), assembly (GTs genes), translocation (ABC transporter genes), sulfation (PAPS biosynthesis and sulfotransferase genes) and lipid carrier biosynthesis (wcb operon). Comparative analysis of the CPS BGCs from available Cobetia genomes showed the presence of KMM 1449-like CPS BGC among strains of all three Cobetia species. The study of new natural sulfated polysaccharides, as well as the elucidation of the pathways of their biosynthesis, provides the basis for the development of potential anticancer drugs.

Two novel strains, CB1-14^T and CB2-10, were isolated from the marine polychaetes Chaetopterus cautus from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA sequences revealed that the two strains belong to the genus Vibrio, sharing 98.96% identity with Vibrio hangzhouensis CN 83^T. MLSA using five protein-coding genes (ftsZ, gyrA, gyrB, mreB, and rpoA) showed that CB1-14^T and CB2-10 are closely related to the members of the Mediterranei clade, namely Vibrio mediterranei CECT 621^T, Vibrio barjaei 3062^T, Vibrio thalassae CECT 8203^T, Vibrio hangzhouensis CGMCC 1.7062^T, Vibrio maritimus CAIM 1455^T, and Vibrio variabilis CAIM 1454^T. Based on both MLST neighbor-net phylogenetic network and phylogenomic tree results, they fell into the subclade formed by V. maritimus CAIM 1455^T and V. variabilis CAIM 1454^T. Both new strains CB1-14^T and CB2-10 showed the highest ANI/AAI values of 91.3%/92.7% with V. variabilis CAIM 1454^T and 90.3%/93.1% with V. maritimus CAIM 1455^T. The dDDH values between strain CB1-14^T and the members of the Mediterranei clade ranged from 20.9% to 45.7%. Major fatty acids were C_16:1ω9c, C_16:1ω7c, and C_18:1ω9c, followed by C_16:0 and C_18:1ω7c. The genome of CB1-14^T is 5,591,686 bp in size, with DNA G+C content of 46.1%. It consists of two circular chromosomes (3,497,892 and 1,804,652 bp) and one plasmid (241,015 bp) and comprises 4782 protein-coding genes and 10 rrn operons. The CB1-14^T and CB2-10 genomes were enriched in CAZyme-encoding genes of the following families: GH1, GH3, GH13, GH23, GH43, GH94, PL17, and CE4, indicating the potential to catabolize alginate, xylan, and chitin, common polysaccharides in marine ecosystems. Based on the combined phylogenomic analyses and phenotypic properties, a new species, Vibrio chaetopteri sp. nov., is proposed, with CB1-14^T = (KMM 8419^T = KCTC 92790^T) as the type strain.

Vibrio sp. KMM 8419 (=CB1-14) is a Gram-negative bacterium isolated from a food-net mucus sample of marine polychaete Chaetopterus cautus collected in the Sea of Japan. Here, we report the structure and biosynthetic gene cluster of the capsular polysaccharide (CPS) from strain KMM 8419. The CPS was isolated and studied by one- and two-dimensional ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The molecular weight of the CPS was about 254 kDa. The CPS consisted of disaccharide repeating units of D-glucose and sulfated and acetylated L-rhamnose established as →2)-α-L-Rhap3S4Ac-(1→6)-α-D-Glcp-(1→. To identify the genes responsible for CPS biosynthesis, whole-genome sequencing of KMM 8419 was carried out. Based on the genome annotations together with the Interproscan, UniProt and AntiSMASH results, a CPS-related gene cluster of 80 genes was found on chromosome 1. This cluster contained sets of genes encoding for the nucleotide sugar biosynthesis (UDP-Glc and dTDP-Rha), assembly (glycosyltransferases (GT)), transport (ABC transporter) and sulfation (PAPS biosynthesis and sulfotransferases) of the sulfated CPS. A hypothetical model for the assembly and transportation of the sulfated CPS was also proposed. In addition, this locus included genes for O-antigen biosynthesis. Further studies of biological activity, the structure–activity relationship in the new sulfated polysaccharide and its biosynthesis are necessary for the development of potent anticancer agents or drug delivery systems.

Two marine bacteria, designated strains 4Alg 33^Tand 3Alg 14/1, were isolated from brown (Saccharina japonica) and green (Ulva fenestrata) macroalgae, respectively. These isolates were aerobic Gram-negative rods exhibiting a gliding motility. The 16S rRNA gene phylogenetic analysis clearly showed their belonging to the genus Formosa, the family Flavobacteriaceae, and the phylum Bacteroidota. The closest relatives of the new strains were Formosa undariae KCTC 32328^T (99.05%), Formosa arctica IMCC 9485^T (99.05%) and Formosa agariphila KMM 3901^T (98.96%). The ANI and dDDH values between the two new strains were 97.9% and 85.3%, respectively. The AAI values between 4Alg 33^T and Formosa type strains ranged from 80.1% (Formosa haliotis MA1^T) to 91.4% (F. undariae KCTC 32328^T). The cellular fatty acid and polar lipid profiles of the new isolates were generally similar to those of the type strains of Formosa species. The genomes of 4Alg 33^T and 3Alg 14/1 are represented by a circular chromosome of 4,157,724 bp and 4,316,096 bp in size with 3536 and 3879 protein-coding genes, respectively. They shared a DNA G+C content of 34.3 mol% and comprised four rrn operons. The pangenome of the genus Formosa belongs to the open type and is characterized by an abundance of CAZymes. The proportion of CAZyme genes in novel genomes was more than 5%, with a prevalence of glycoside hydrolase genes, suggesting great potential for utilizing marine-derived polysaccharides. Based on the results of polyphasic characterization, the two algal isolates represent a distinct species lineage within the genus Formosa, for which we propose the name Formosa bonchosmolovskayae sp. nov. with the type strain 4Alg 33^T (= KMM 3963^T = KCTC 72008^T). In addition, we have proposed to transfer Formosa maritima Cao et al. 2020 and Bizionia arctica Li et al. 2015 to the genus Xanthomarina Vaidya et al. 2015 as Xanthomarina maritima comb. nov. and Xanthomarina arctica comb. nov. based on a combination of the genomic and phenotypic characteristics.