Intracellular fucoidanase was isolated from the marine bacterium, Formosa algae strain KMM 3553. The first appearance of fucoidan enzymatic hydrolysis products in a cell-free extract was detected after 4 h of bacterial growth, and maximal fucoidanase activity was observed after 12 h of growth. The fucoidanase displayed maximal activity in a wide range of pH values, from 6.5 to 9.1. The presence of Mg²⁺, Ca²⁺ and Ba²⁺ cations strongly activated the enzyme; however, Cu²⁺ and Zn²⁺ cations had inhibitory effects on the enzymatic activity. The enzymatic activity of fucoidanase was considerably reduced after prolonged (about 60 min) incubation of the enzyme solution at 45 °C. The fucoidanase catalyzed the hydrolysis of fucoidans from Fucus evanescens and Fucus vesiculosus, but not from Saccharina cichorioides. The fucoidanase also did not hydrolyze carrageenan. Desulfated fucoidan from F. evanescens was hydrolysed very weakly in contrast to deacetylated fucoidan, which was hydrolysed more actively compared to the native fucoidan from F. evanescens. Analysis of the structure of the enzymatic products showed that the marine bacteria, F. algae, synthesized an α-l-fucanase with an endo-type action that is specific for 1→4-bonds in a polysaccharide molecule built up of alternating three- and four-linked α-l-fucopyranose residues sulfated mainly at position 2.

Fucoidans belong to a structurally heterogeneous class of sulfated polysaccharides isolated from brown algae. They have a wide spectrum of biological activities. The complex structures of these polysaccharides hinder structure-activity relationships determination. Fucoidan sulfatases can make useful tools for the determination of the fine chemical structure of fucoidans. In this study, identification and preparation of two recombinant sulfatases able to catalyze the cleavage of sulfate groups from fragments of fucoidan molecules is described for the first time. Two genes of sulfatases swf1 and swf4 of the marine bacterium Wenyingzhuangia fucanilytica CZ1127^T were cloned and the proteins were produced in Escherichia coli cells. Sulfatases SWF1 and SWF4 are assigned to S1_17 and S1_25 subfamilies of formylglycine-dependent enzymes of S1 family (SulfAtlas). Some molecular and biochemical characteristics of recombinant fucoidan sulfatases have been studied. Detailed specificity and catalytic features of sulfatases were determined using various sulfated fucooligosaccharides. Structures of products produced by SWF1 and SWF4 were established by nuclear magnetic resonance (NMR) spectroscopy. Based on the obtained data, the enzymes are classified as fucoidan exo-2O-sulfatase (SWF1) and fucoidan exo-3O-sulfatase (SWF4). In addition, we demonstrated the sequential action of sulfatases on 2,3-di-O-sulfated fucooligosacchrides, which indicates an exolitic degradation pathway of fucoidan by a marine bacterium W. fucanilytica CZ1127^T.

Twenty-three bacterial strains were isolated from the secreted mucus trapping net of the marine polychaete Chaetopterus variopedatus (phylum Annelida) and twenty strains were identified using 16S rRNA gene analysis. Strain CB1-14 was recognized as a new species of the genus Vibrio using the eight-gene multilocus sequence analysis (MLSA) and genome sequences of nineteen type Vibrio strains. This Vibrio sp. was cultured, and 6-epi-monanchorin (2), previously isolated from the polychaete and two sponge species, was found in the cells and culture broth. The presence of the 6-epi-monanchorin was confirmed by its isolation followed by ¹H NMR and HRESIMS analysis. These results showed the microbial origin of the bicyclic guanidine alkaloid 2 in C. variopedatus.

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.

The taxonomic status of two gram-negative, whitish-pigmented motile bacteria KMM 9576^T and KMM 9553 isolated from a sandy sediment sample from the Sea of Japan seashore was defined. Phylogenetic analysis revealed that strains KMM 9576^T and KMM 9553 represent a distinct lineage within the family Rhizobiaceae, sharing 100% 16S rRNA sequence similarity and 99.5% average nucleotide identity (ANI) to each other. The strains showed the highest 16S rRNA sequence similarities of 97.4% to Sinorhizobium garamanticum LMG 24692^T, 96.9% to Ensifer adhaerens NBRC 100388^T, and 96.8% to Pararhizobium giardinii NBRC 107135^T. The ANI values between strain KMM 9576^T and Ensifer adhaerens NBRC 100388^T, Sinorhizobium fredii USDA 205^T, Pararhizobium giardinii NBRC 107135^T, and Rhizobium leguminosarum NBRC 14778^T were 79.9%, 79.6%, 79.4%, and 79.2%, respectively. The highest core-proteome average amino acid identity (cpAAI) values of 82.1% and 83.1% were estimated between strain KMM 9576^T and Rhizobium leguminosarum NBRC 14778^T and ‘Rhizobium album’ NS-104, respectively. The DNA GC contents were calculated from a genome sequence to be 61.5% (KMM 9576^T) and 61.4% (KMM 9553). Both strains contained the major ubiquinone Q-10 and C_18:1ω7c as the dominant fatty acid followed by 11-methyl C_18:1ω7c and C_19:0 cyclo, and polar lipids consisted of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminophospholipid, and two unidentified phospholipids. Based on phylogenetic and phylogenomic analyses, and phenotypic characterization, strains KMM 9576^T and KMM 9553 are concluded to represent a novel genus and species, for which the name Fererhizobium litorale gen. nov., sp. nov. is proposed. The type strain of the type species is strain KMM 9576^T (=NRIC 0957^T).

A comparative study of the adhesion of epiphytic bacteria and marine free-living, saprophytic, and pathogenic bacteria on seagrass leaves and abiotic surfaces was performed to prove the occurrence of true epiphytes of Zostera marina and to elucidate the bacterium-plant symbiotrophic relationships. It was shown that in the course of adhesion to the seagrass leaves of two taxonomically different bacteria, Cytophaga sp. KMM 3552 and Pseudoalteromonas citrea KMM 461, isolated from the seagrass surface, the number of viable cells increased 3–7-fold after 60 h of incubation, reaching 1.0–2.0 × 10⁵ cells/cm²; however, in the case of adhesion of these bacteria to abiotic surfaces, such as glass or metal, virtually no viable cells were observed after 60 h of incubation. Such selectivity of cell adhesion was not observed in the case of three other bacterial species studied, viz., Vibrio alginolyticus KMM 3551, Bacillus subtilis KMM 430, and Pseudomonas aeruginosa KMM 433. The amount of viable cells of V. alginolyticus KMM 3551 absorbed on glass and metal surfaces increased twofold after 40 h of incubation. The cells of saprophytic B. subtilis KMM 430 and pathogenic P. aeruginosa KMM 433 adsorbed on three studied substrata remained viable for 36 h and died by the 60th hour of incubation.