Metabolomics and Molecular Networking-Guided Screening of Bacillus-Derived Bioactive Compounds Against a Highly Lethal Vibrio Species.

Microorganisms are important sources of bioactive natural products. However, the complexity of microbial metabolites and the low abundance of active compounds render the isolation and purification process laborious and inefficient. During our search for active substances capable of inhibiting the newly discovered highly lethal Vibrio strain vp-HL, we found that the fermentation broth of multiple Bacillus strains exhibited antibacterial activity. However, the substances responsible for the activity remained unclear. Metabolomics, molecular networking (MN), and the Structural similarity Network Annotation Platform for Mass Spectrometry (SNAP-MS) were employed in conjunction with bioactivity screening to predict the antibacterial compounds from Bacillus strains. The analysis of fractions, and their isolation, NMR-based annotation, and bioactivity evaluation of an amicoumacin compound partially confirmed the prediction from these statistical analyses. This work presents the potential of marine Bacillus in producing active substances against Vibrio species. Additionally, it highlighted the significance and feasibility of metabolomics and MN in the dereplication of compounds and the determination of isolation targets.

Evolution and adaptation of terrestrial plant-associated Plantibacter species into remote marine environments.

Microbes are thought to be distributed and circulated around the world, but the connection between marine and terrestrial microbiomes remains largely unknown. We use Plantibacter, a representative genus associated with plants, as our research model to investigate the global distribution and adaptation of plant-related bacteria in plant-free environments, particularly in the remote Southern Ocean and the deep Atlantic Ocean. The marine isolates and their plant-associated relatives shared over 98% whole-genome average nucleotide identity (ANI), indicating recent divergence and ongoing speciation from plant-related niches to marine environments. Comparative genomics revealed that the marine strains acquired new genes via horizontal gene transfer from non-Plantibacter species and refined existing genes through positive selection to improve adaptation to new habitats. Meanwhile, marine strains retained the ability to interact with plants, such as modifying root system architecture and promoting germination. Furthermore, Plantibacter species were found to be widely distributed in marine environments, revealing an unrecognized phenomenon that plant-associated microbiomes have colonized the ocean, which could serve as a reservoir for plant growth-promoting microbes. This study demonstrates the presence of an active reservoir of terrestrial plant growth-promoting bacteria in remote marine systems and advances our understanding of the microbial connections between plant-associated and plant-free environments at the genome level.

Transfer of Thermobacterium salinum Chen et al. 2023 to the genus Luteirhabdus Ren et al. 2022 as Luteirhabdus salina comb. nov.

The 16S rRNA gene of Thermobacterium salinum TK19130T had the highest sequence similarity to that of Luteirhabdus pelagi A3-108T (99.7%). Phylogeny of 16S rRNA gene and whole genome sequences indicated that T. salinum TK19130T and L. pelagi A3-108T are closely related, and represented an independent clade. Whole genome comparisons showed that T. salinum TK19130T and L. pelagi A3-108T shared average amino acid identity of 95.3%, indicating they could be merged into the same genus. The digital DNA-DNA hybridization and average nucleotide identity values between T. salinum TK19130T and L. pelagi A3-108T were 52.5 and 93.3%, respectively. These values were below the recommended threshold values of prokaryotic species delineation. Thus, based on the principle of priority, we proposed the transfer of Thermobacterium salinum Chen et al. 2023 to the genus Luteirhabdus Ren et al. 2022 as Luteirhabdus salina comb. nov.

Thioclava arctica sp. nov. and Zhongshania arctica sp. nov., isolated from the surface sediment of the Arctic Ocean and reclassification of Marortus luteolus Yu et al. 2019 as a later heterotypic synonym of Zhongshania marina On et al. 2019.

Two Gram-stain-negative bacterial strains, 15-R06ZXC-3T and R06B22T, were isolated from the surface sediment of the Arctic Ocean. Phylogenetic analyses based on the 16S rRNA gene and genome sequences indicated that strain 15-R06ZXC-3T belongs to the genus Thioclava, while strain R06B22T belongs to the genus Zhongshania. Strain 15-R06ZXC-3T showed the closest relationship to Thioclava indica DT23-4T. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain 15-R06ZXC-3T and all of the type strains of the genus Thioclava ranged from 20.8 to 30.4% and 79.1 to 85.7%, respectively. Strain R06B22T was most closely related to Zhongshania marina DSW25-10T. The dDDH and ANI values between strain R06B22T and all of the type strains of the genus Zhongshania ranged from 18.6 to 20.4% and 77.5 to 79.4%, respectively. These dDDH and ANI values were all below the standard cutoff criteria for the delineation of bacterial species, indicating that the two strains may represent novel species within their respective genera. Furthermore, their phenotypic and chemotaxonomic characteristics also differentiated them from closely related species. Based on the polyphasic analyses, strains 15-R06ZXC-3T and R06B22T separately represent novel species of the genera Thioclava and Zhongshania, for which the names Thioclava arctica sp. nov. (type strain 15-R06ZXC-3T = MCCC 1A07434T= KCTC 8342T) and Zhongshania arctica sp. nov. (type strain R06B22T = MCCC 1A08273T= KCTC 8343T) are proposed. Additionally, phylogenomic analyses showed that the strain Marortus luteolus ZX-21T was clustered with the strain Z. marina DSW25-10T and all other type strains of the genus Zhongshania. Furthermore, the ANI and dDDH values between strains ZX-21T and DSW25-10T were 97.6% and 78.8±2.5%, respectively, strongly indicating that they represented a single species. Therefore, it is proposed that M. luteolus Yu et al. 2019 be recognized as a later heterotypic synonym of Z. marina On et al. 2019.

Aequorivita flava sp. nov., isolated from deep-sea sediments.

Three Gram-stain-negative, aerobic, non-motile, chemoheterotrophic, short-rod-shaped bacteria, designated CDY1-MB1T, CDY2-MB3, and BDY3-MB2, were isolated from three marine sediment samples collected in the eastern Pacific Ocean. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these strains were related to the genus Aequorivita and close to the type strain of Aequorivita vitellina F4716T (with similarities of 98.0-98.1%). Strain CDY1-MB1T can grow at 15-37 °C (optimum 30 °C) and in media with pH 6-9 (optimum, pH 7), and tolerate up to 10% (w/v) NaCl. The predominant cellular fatty acids of strain CDY1-MB1T were iso-C15 : 0 (20.7%) and iso-C17 : 0 3-OH (12.8%); the sole respiratory quinone was menaquinone 6; the major polar lipids were phosphatidylethanolamine, two unidentified aminolipids and two unidentified polar lipids. The digital DNA-DNA hybridization/average nucleotide identity values between strains CDY1-MB1T, CDY2-MB3, and BDY3-MB2 and A. vitellina F4716T were 24.7%/81.6-81.7%, thereby indicating that strain CDY1-MB1T should represent a novel species of the genus Aequorivita. The genomic DNA G+C contents were 37.6 % in all three strains. Genomic analysis showed the presence of genes related to nitrogen and sulphur cycling, as well as metal reduction. The genetic traits of these strains indicate their possible roles in nutrient cycling and detoxification processes, potentially shaping the deep-sea ecosystem's health and resilience. Based upon the consensus of phenotypic and genotypic analyses, strain CDY1-MB1T should be classified as a novel species of the genus Aequorivita, for which the name Aequorivita flava sp. nov. is proposed. The type strain is CDY1-MB1T (=MCCC 1A16935T=KCTC 102223T).

Isolation and Characterization of Paracoccus maritimus sp. nov., from Intertidal Sediment.

A novel Paracoccus-related strain, designated YLB-12T, was isolated from a sediment sample from the tidal zone of Shapowei Port, Xiamen, Fujian Province, PR China. The novel strain is a Gram-stain-negative, short, rod-shaped, nonmotile, catalase- and oxidase-positive strain that grows at 10-37 °C and pH 5.0-9.0 in the presence of 0-12.0% (w/v) NaCl. Phylogenetic analysis of the 16S rRNA gene sequences indicated that this strain belongs to the genus Paracoccus and that its highest sequence similarity was to Paracoccus homiensis DD-R11T (98.5%), followed by Paracoccus zeaxanthinifaciens ATCC 21588T (97.4%), Paracoccus rhizosphaerae LMG 26205T (97.2%), Paracoccus beibuensis CGMCC 1.7295T (97.1%) and Paracoccus halotolerans CFH 90064T (97.0%). The DNA‒DNA hybridization values between strain YLB-12T and the five closely related type strains ranged from 20.4 to 22.4%. The genomic G+C content of strain YLB-12T was 63.7%. In addition to diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and phosphatidylglycerol, the polar lipids of the strain YLB-12T also consisted of an unidentified glycolipid and four unidentified polar lipids. The cells contained summed feature 8 (C18: 1ω6c /C18: 1ω7c, 62.7%) as the major cellular fatty acid and ubiquinone-10 as the predominant menaquinone. On the basis of its phenotypic and genotypic characteristics, strain YLB-12T represents a novel species within the genus Paracoccus, for which the name Paracoccus maritimus sp. nov. is proposed. The type strain was YLB-12T (= MCCC 1A17213T = KCTC 82197T).

Cytotoxic Pentaketide-Sesquiterpenes from the Marine-Derived Fungus Talaromyces variabilis M22734.

Talaromyces, a filamentous fungus widely distributed across terrestrial and marine environments, can produce a diverse array of natural products, including alkaloids, polyketones, and polyketide-terpenoids. Among these, chrodrimanins represented a typical class of natural products. In this study, we isolated three previously undescribed pentaketide-sesquiterpenes, 8,9-epi-chrodrimanins (1-3), along with eight known compounds (4-11). The structures of compounds 1-3 were elucidated using nuclear magnetic resonance (NMR) and mass spectrometry (MS), while their absolute configurations were determined through X-ray crystallography and electronic circular dichroism (ECD) computations. The biosynthetic pathways of compounds 1-3 initiate with 6-hydroxymellein and involve multiple stages of isoprenylation, cyclization, oxidation, and acetylation. We selected four strains of gastrointestinal cancer cells for activity evaluation. We found that compound 3 selectively inhibited MKN-45, whereas compounds 1 and 2 exhibited no significant inhibitory activity against the four cell lines. These findings suggested that 8,9-epi-chrodrimanins could serve as scaffold compounds for further structural modifications, potentially leading to the development of targeted therapies for gastric cancer.

A Semisynthesis Platform for the Efficient Production and Exploration of Didemnin-Based Drugs.

Plitidepsin (or dehydrodidemnin B), an approved anticancer drug, belongs to the didemnin family of cyclic depsipeptides, which are found in limited quantities in marine tunicate extracts. Herein, we introduce a new approach that integrates microbial and chemical synthesis to generate plitidepsin and its analogues. We screened a Tistrella strain library to identify a potent didemnin B producer, and then introduced a second copy of the didemnin biosynthetic gene cluster into its genome, resulting in a didemnin B titer of approximately 75 mg/L. Next, we developed two straightforward chemical strategies to convert didemnin B into plitidepsin, one of which involved a one-step synthetic route giving over 90 % overall yield. Furthermore, we synthesized 13 new didemnin derivatives and three didemnin probes, enabling research into structure-activity relationships and interactions between didemnin and proteins. Our study highlights the synergistic potential of biosynthesis and chemical synthesis in overcoming the challenge of producing complex natural products sustainably and at scale.

Mangrovimonas aestuarii sp. nov., isolated from tidal flat sediment.

A Gram-stain-negative, rod-shaped and light yellow-pigmented strain designated MBT5T was isolated from tidal flat sediment of an oyster farming area in Quanzhou Bay, PR China. Catalase activity and oxidase activity were positive. Flexirubin-type pigment was absent. Growth was observed at 10-40 °C (optimum, 35 °C), pH 6-9 (optimum, pH 7), and with 1-7 % NaCl (optimum, 2 %, w/v). The 16S rRNA gene of strain MBT5T had maximum sequence similarity values with Meridianimaribacter flavus NH57NT, Mangrovimonas yunxiaonensis LYYY01T and Mangrovimonas futianensis AS18T of 95.6, 95.4 and 94.9 %, respectively. Phylogenetic analysis based on 16S rRNA gene sequences and 120 conserved concatenated proteins indicated that strain MBT5T was affiliated to the genus Mangrovimonas and formed a distinct monophyletic branch. The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values between strain MBT5T and the type strains of Mangrovimonas were estimated to be 17.3-18.7 %, 70.9-71.5 % and 66.4-68.2 %, respectively. The respiratory quinone was menaquinone-6. The major fatty acids were iso-C15 : 0 and iso-C15 : 1 G. The draft genome size was 2 952 053 bp with a DNA G+C content of 36.5 %. Based on phenotypic, physiological, phylogenetic and genomic data, together with chemotaxonomic characteristics, strain MBT5T represents a novel species, for which the name Mangrovimonas aestuarii sp. nov. is proposed. The type strain is MBT5T (=MCCC 1K06186T=KCTC 92888T=GDMCC 1.3851T).

Sneathiella marina sp. nov., isolated from a sea anemone in the Western Pacific Ocean.

A novel marine bacterium designated strain PHK-P5T was isolated from a sea anemone (Actinostolidae sp. 1). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain PHK-P5T belonged to the genus Sneathiella. The bacterium was Gram-stain-negative, aerobic, oxidase- and catalase- positive, oval- to rod-shaped, and motile. Growth was observed at pH 6.0-9.0, salinities of 2.0-9.0 % and temperatures of 4-37 °C. The G+C content of the chromosomal DNA was 49.2 %. The respiratory quinone was determined to be Q-10. The principal fatty acids of strain PHK-P5T were C19 : 0cyclo ω8c (25.19 %), C16 : 0 (22.76 %), summed feature 8 (C18 : 1 ω7c/ω6c; 16.14 %), C14 : 0 (8.81 %), C17 : 0cyclo (8.10 %), summed feature 2 (C12 : 0 aldehyde and/or unknown 10.928; 7.19 %) and C18 : 1 ω7c 11-methyl (5.03 %). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The average nucleotide identity and digital DNA-DNA hybridization values among the genomes of strain PHK-P5T and the reference strains were 68.7-70.9 % and 17.4-18.1 %, respectively. The combined genotypic and phenotypic data showed that strain PHK-P5T represents a novel species within the genus Sneathiella, for which the name Sneathiella marina sp. nov. is proposed, with the type strain PHK-P5T (=MCCC M21824T=KCTC 82924T).

Gramella oceanisediminis sp. nov., isolated from deep-sea sediment of the Indian Ocean.

A taxonomic study was carried out on strain GC03-9T, which was isolated from deep-sea sediment of the Indian Ocean. The bacterium was Gram-stain-negative, catalase-positive, oxidase-negative, rod-shaped and gliding motile. Growth was observed at salinities of 0-9 % and at temperatures of 10-42 °C. The isolate could degrade gelatin and aesculin. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain GC03-9T belonged to the genus Gramella, with the highest sequence similarity to Gramella bathymodioli JCM 33424T (97.9 %), followed by Gramella jeungdoensis KCTC 23123T (97.2 %) and other species of the genus Gramella (93.4-96.3 %). The average nucleotide identity and the digital DNA-DNA hybridization estimate values between strain GC03-9T and G. bathymodioli JCM 33424T and G. jeungdoensis KCTC 23123T were 25.1 and 18.7 % and 82.47 and 75.69 %, respectively. The principal fatty acids were iso-C15 : 0 (28.0 %), iso-C17 : 0 3OH (13.4 %), summed feature 9 (iso-C17 : 1 ω9c and/or 10-methyl C16 : 0; 13.3 %) and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c; 11.0 %). The G+C content of the chromosomal DNA was 41.17 mol%. The respiratory quinone was determined to be menaquinone-6 (100 %). Phosphatidylethanolamine, one unknown phospholipid, three unknown aminolipids and two unknown polar lipids were present. The combined genotypic and phenotypic data showed that strain GC03-9T represents a novel species within the genus Gramella, for which the name Gramella oceanisediminis sp. nov. is proposed, with the type strain GC03-9T (=MCCC M25440T=KCTC 92235T).

Thermomonas mangrovi sp. nov., isolated from soil of a mangrove nature reserve.

A Gram-stain-negative, non-motile, aerobic and ovoid-rod-shaped bacterial strain, designated as 2C3345T, was isolated from soil of a mangrove nature reserve in Shenzhen, PR China and its taxonomic position was investigated. The 16S rRNA gene sequence of strain 2C3345T exhibited the highest similarity value to that of the type strains Thermomonas aquatica NBRC 113114T (98.4 %), Thermomonas carbonis KCTC 42013T (98.1 %), Thermomonas brevis DSM 15422T (98.0 %) and Thermomonas haemolytica DSM 13605T (97.9 %). Strain 2C3345T grew optimally at 28-30 °C, pH 7.0 and without NaCl. The predominant ubiquinone in 2C3345T was identified as Q-8. The major fatty acids of 2C3345T were iso-C15 : 0, iso-C16 : 0 and summed feature 9 (is0-C17:1ω9c and/or 10-methyl C16:0). The major polar lipids of 2C3345T were phosphatidylcholine (PC), phosphatidylglycerol (PG), diphosphatidglycerol (DPG), phosphatidylethanolamine (PE), an unidentified phospholipid, an unidentified aminolipid and two unidentified lipids. The DNA G+C content of strain 2C3345T was 69.9 %. The draft genome sequence of 2C3345T included 2 888 645 bp in total (N50=310 730 bp) with a medium read coverage of 388.6×and 21 scaffolds. In silico DNA-DNA hybridisation with type strains of species of the genus Thermomonas showed 24.4, 22.4, 24.1 and 23.2% relatedness to T. aquatica NBRC 113114T, T. carbonis KCTC 42013T, T. brevis DSM 15422T and T. haemolytica DSM 13605T, respectively. And the average nucleotide identity by blast (ANIb) values between 2C3345T and these four reference strains were 81.9, 80.0, 81.2 and 80.6 %, respectively, lower than the 95-96% threshold value for dividing prokaryotic species. On the basis of its phenotypic, chemotaxonomic, phylogenetic and phylogenomic properties, strain 2C3345T is considered to represent a novel species within the genus Thermomonas, for which the name Thermomonas mangrovi sp. nov. is proposed. The type strain is 2C3345T (=KCTC 92730T =MCCC 1K08335T).

Bacillus changyiensis sp. nov., isolated from coastal sediment.

Two Gram-stain-positive, facultatively anaerobic, motile, endospore-forming, rod-shaped bacteria, designated CLL-3-40T and CLL-7-23, were isolated from coastal sediment sampled in Changyi, Shandong Province, PR China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these strains were related to the genus Bacillus and close to six type strains of species within the Bacillus licheniformis group. In phenotypic characterization tests, strain CLL-3-40T could grow at 15-50 °C (optimum, 37 °C) and in media with pH 5-9 (optimum pH 7.0), and tolerate up to 12 % (w/v) NaCl. The fermentation broth supernatant extracted by ethyl acetate of strain CLL-3-40T could inhibit aquaculture pathogenic vibrios. The predominant cellular fatty acids of strain CLL-3-40T were anteiso-C15 : 0 (30.7 %) and iso-C15 : 0 (31.5 %); the peptidoglycan from cell-wall contained meso-diaminopimelic acid; the predominant quinone was menaquinone 7; and the major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, an unidentified glycolipid and two unidentified phospholipids. The digital DNA-DNA hybridization values and average nucleotide identities among strains CLL-3-40T and CLL-7-23 and their close type strains were less than 21.9 and 48.4 %, respectively, thereby indicating that strain CLL-3-40T should represent a novel species of the genus Bacillus. The genomic DNA G+C contents were 38.4 mol% in strain CLL-3-40T and 38.3 mol% in strain CLL-7-23. The 12 biosynthetic gene clusters of strain CLL-3-40T were predicted based on results from the online server antiSMASH. Based upon the consensus of phenotypic and genotypic results, strain CLL-3-40T should be classified as representing a novel species of the genus Bacillus, for which the name Bacillus changyiensis sp. nov. is proposed. The type strain is CLL-3-40T (= MCCC 1A14857T=JCM 35755T).

Alcanivorax xiamenensis sp. nov., a novel marine hydrocarbonoclastic bacterium isolated from surface seawater.

A novel Alcanivorax-related strain, designated 6-D-6T, was isolated from the surface seawater collected around Xiamen Island. The novel strain is Gram-stain-negative, rod-shaped and motile, and grows at 10-45 °C, pH 6.0-9.0 and in the presence of 0.5-15.0 % (w/v) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that it belongs to the genus Alcanivorax, with the highest sequence similarity to Alcanivorax dieselolei B5T (99.9 %), followed by Alcanivorax xenomutans JC109T (99.5 %), Alcanivorax balearicus MACL04T (99.3 %) and other 13 species of the genus Alcanivorax (93.8 %-95.6 %). The digital DNA-DNA hybridization and average nucleotide identity values between strain 6-D-6T and three close type strains were 40.1-42.9/90.6-91.4 %, and others were below 22.9/85.1 %, respectively. The novel strain contained major cellular fatty acids of C16 : 0 (31.0 %), C19 : 0 ω8c cyclo (23.5 %), C17 : 0 cyclo (9.7 %), C12 : 0 3OH (8.6 %), summed feature 8 (7.6 %) and C12 : 0 (5.4 %). The genomic G+C content of strain 6-D-6T was 61.38 %. Phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, two unidentified phospholipids and one amino-group-containing phospholipid were detected. On the basis of phenotypic and genotypic characteristics, strain 6-D-6T represents a novel species within the genus Alcanivorax, for which the name Alcanivorax xiamenensis sp. nov. is proposed. The type strain is 6-D-6T (=MCCC 1A01359T=KCTC 92480T).

Salipiger pentaromativorans sp. nov., a polycyclic aromatic hydrocarbon-degrading bacterium isolated from mangrove sediment.

Polycyclic aromatic hydrocarbons (PAHs) have been recognized as a potential health risk and are widespread in nature due to their intrinsic chemical stability and high recalcitrance to degradation. A taxonomic study was carried out on strain P9T, which was isolated from a PAH-degrading consortium, enriched from the mangrove sediment from Zhangzhou, PR China. The isolate was chemoheterotrophic, aerobic, Gram-stain-negative, short-rod shaped, and motile by one polar flagellum. Growth was observed at salinities from 0.5-6.0 % (optimum, 3 %), at pH 4-9 (optimum, pH 7) and at 10-41 °C (optimum, 25-30 °C). It did not synthesize bacteriochlorophyll a. Catalase and oxidase activities were positive. Acid was produced from starch, amygdalin, arbutin, cellobiose, d-fructose, maltose, d-mannitol, melezitose, melibiose, raffinose, d-ribose, sucrose, trehalose, d-xylose, aesculin ferric citrate, gentiobiose, glycogen, l-arabinose, l-rhamnose, methyl α-d-glucopyranoside, methyl ß-d-xylopyranoside, N-acetylglucosamine and salicin, and weakly positive for d-arabitol, d-galactose, lactose, turanose and glycerol. Phylogenetic analysis revealed that strain P9T fell within the clade comprising the type strains of Salipiger species and formed an independent cluster with Salipiger profundus, which was distinct from other members of the family Rhodobacteraceae. The 16S rRNA gene sequence comparisons showed that strain P9T was most closely related to Salipiger bermudensis HTCC 260T (96.7 %), and other species of the genus Salipiger (95.7-94.2 %). Strain P9T had the highest digital DNA-DNA hybridization value with S. profundus CGMCC 1.12377T (25.0 %) and the highest average nucleotide identity (ANIb and ANIm) values with S. profundus CGMCC 1.12377T(80.3 and 85.8 %, respectively). The sole respiratory quinone was quinone 10. The dominant fatty acids were C18 : 1 ω7c (61.4 %), C16 : 0 (17.5 %) and C19 : 0 ω8c cyclo (7.6 %). The G+C content of the chromosomal DNA was 65.8 mol%. In the polar lipid profile, phospholipid, phosphatidylglycerol, aminolipid, glycolipid and phosphatidylethanolamine were the major compounds. Based on the phenotypic and phylogenetic data, strain P9T represents a novel species of the genus Salipiger, for which the name Salipiger pentaromativorans sp. nov. is proposed. The type strain is P9T (=CCTCC AB 209290T=LMG 25701T=MCCC 1F01055T).

Pseudophaeobacter profundi sp. nov., isolated from the Western Pacific Ocean.

A novel Gram-stain-negative, facultatively anaerobic and heterotrophic bacterium, designated strain ZH257T, was isolated from in situ enrichment samples incubated on the seamount floor of the Western Pacific Ocean. Cells were rod-shaped, oxidase- and catalase- positive, and motile by means of polar flagella. Strain ZH257T grew at 4-37 °C (optimum, 28-32 °C), pH 6.0-9.0 (optimum, pH 7.0) and with 2.0-9.0 % (w/v) NaCl (optimum, 3.0-4.0 %). Strain ZH257T was most closely related to members of the genus Pseudophaeobacter, sharing 99.13, 98.27 and 96.89 % 16S rRNA gene sequence identities with Pseudophaeobacter flagellatus GDMCC 1.2988T, Pseudophaeobacter arcticus DSM 23566T and Pseudophaeobacter leonis DSM 25627T, respectively. The DNA G+C content was 59.2 mol%. The estimated average nucleotide identity and digital DNA-DNA hybridization values between strain ZH257T and its closely related species were 79.61-93.04 % and 23.10-50.20 %, respectively. Strain ZH257T harboured complete denitrification and nitrate assimilation pathways. Strain ZH257T contained summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) as major fatty acids (>5 %), and Q-10 as the major respiratory quinone. The polar lipid profile contained phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, an unidentified phospholipid, an unidentified aminolipid and four unidentified lipids. The combined phenotypic, genotypic and chemotaxonomic data showed that strain ZH257T represents a novel species of the genus Pseudophaeobacter, for which the name Pseudophaeobacter profundi sp. nov. is proposed, with the type strain ZH257T (=MCCC M29024T=KACC 23147T).

Galbibacter pacificus sp. nov., isolated from surface seawater of the western Pacific Ocean and transfer of Joostella marina to the genus Galbibacter as Galbibacter orientalis nom. nov. and emended description of the genus Galbibacter.

Two Gram-stain-negative, non-motile, non-spore-forming, strictly aerobic and rod-shaped bacterial strains, CMA-7T and CAA-3, were isolated from surface seawater samples collected from the western Pacific Ocean. Phylogeny of 16S rRNA gene sequences indicated they were related to the genera Galbibacter and Joostella and shared 95.1, 90.9 and 90.8% sequence similarity with G. mesophilus Mok-17T, J. marina DSM 19592T and G. marinus ck-I2-15T, respectively. Phylogenomic analysis showed that the two strains, together with the members of the genera Galbibacter and Joostella, formed a monophyletic clade that could also be considered a monophyletic taxon. This distinctiveness was supported by amino acid identity and percentage of conserved proteins indices, phenotypic and chemotaxonomic characteristics and comparative genomics analysis. Digital DNA‒DNA hybridization values and average nucleotide identities between the two strains and their closest relatives were 18.0-20.8 % and 77.7-79.3 %, respectively. The principal fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 1 G, Summed Feature 3 (C16 : 1 ω7c/C16 : 1 ω6c or C16 : 1 ω6c/C16 : 1 ω7c), Summed Feature 9 (iso-C17 : 1 ω9c or C16 : 0 10-methyl), and C15 : 0 3-OH. The predominant respiratory quinone was MK-6. The polar lipids were phosphatidylethanolamine, aminolipid, aminophospholipid, phospholipid, phosphoglycolipid, glycolipid and unknown polar lipid. The genomic DNA G+C content of strains CMA-7T and CAA-3 was both 38.4 mol%. Genomic analysis indicated they have the potential to degrade cellulose and chitin. Based on the polyphasic evidence presented in this study, the two strains represent a novel species within the genus Galbibacter, for which the name Galbibacter pacificus sp. nov. is proposed. The type strain is CMA-7T (=MCCC M28999T = KCTC 92588T). Moreover, the transfer of Joostella marina to the genus Galbibacter as Galbibacter orientalis nom. nov. (type strain En5T = KCTC 12518T = DSM 19592T=CGMCC 1.6973T) is also proposed.

Pseudodonghicola flavimaris sp. nov. and Sedimentitalea xiamensis sp. nov., two novel species belonging to the family Roseobacteraceae.

Two Gram-stain-negative, chemoheterotrophic, aerobic bacteria, designated IC7T and JM2-8T, were isolated from seawater of the Yellow Sea of China and rhizosphere soil of mangroves in Xiamen, Fujian, respectively. Phylogenetic analyses based on 16S rRNA gene and genome sequences showed that these two novel strains belonged to the family Roseobacteraceae. Strain IC7T formed a coherent lineage within the genus Pseudodonghicola, showing 98.05 % 16S rRNA gene sequence similarity to Pseudodonghicola xiamenensis Y-2T. Strain JM2-8T was most closely related to members of the genus Sedimentitalea, showing 96.51 and 96.73 % 16S rRNA gene sequence similarities to Sedimentitalea nanhaiensis NH52FT and Sedimentitalea todarodis KHS03T, respectively. The two novel strains contained Q-10 as the major quinone, and phosphatidylethanolamine, aminophospholipid, phosphatidylglycerol and phosphatidylcholine as the principal polar lipids. The main fatty acid of strain IC7T was C19 : 0 cyclo ω8c, while the fatty acid profile JM2-8T was dominated by summed feature 8 containing C18 : 1 ω7c and/or C18 : 1 ω6c. The average nucleotide identity and digital DNA-DNA hybridization values between these two novel isolates and their closely related species were below the cut-off values of 95-96 and 70 %, respectively. The combined genotypic and phenotypic data show that strain IC7T represents a novel species of the genus Pseudodonghicola, for which the name Pseudodonghicola flavimaris sp. nov. is proposed, with the type strain IC7T (=MCCC 1A02763T=KCTC 82844T), and strain JM2-8T represents a novel species of the genus Sedimentitalea, for which the name Sedimentitalea xiamensis sp. nov. is proposed, with the type strain JM2-8T (=MCCC 1A17756T=KCTC 82846T).

Sulfurovum mangrovi sp. nov., an obligately chemolithoautotrophic, hydrogen-oxidizing bacterium isolated from coastal marine sediments.

A novel mesophilic, chemolithoautotrophic, hydrogen-oxidizing bacterium, designated strain ST1-3T, was isolated from mud sediment samples collected from mangroves in Jiulong River estuary. The cells were Gram-stain-negative, non-motile and rod-shaped. The temperature, pH and salinity ranges for growth of strain ST1-3T were 4-45 °C (optimum, 35 °C), pH 5.0-8.5 (optimum, pH 7.0) and 0-8.0 % (w/v) NaCl (optimum, 4.0 %). The isolate was an obligate chemolithoautotroph capable of growth using hydrogen as the only energy source, and molecular oxygen, thiosulphate and elemental sulphur as electron acceptors. The major cellular fatty acids of strain ST1-3T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c). The major polar lipids were phosphatidylethanolamine, phosphatidyldimethyl ethanolamine and phosphatidylglycerol. The respiratory quinone was menaquinone-6. The genomic DNA G+C content was 43.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and core genes showed that the novel isolate belonged to the genus Sulfurovum and was most closely related to Sulfurovum lithotrophicum 42BKTT (94.7 % sequence identity). The average nucleotide identity and digital DNA-DNA hybridization values between ST1-3T and S. lithotrophicum 42BKTT were 74.6 and 16.3 %, respectively. On the basis of the phenotypic, phylogenetic and genomic data presented here, strain ST1-3T represents a novel species of the genus Sulfurovum, for which the name Sulfurovum mangrovi sp. nov. is proposed, with the type strain ST1-3T (=MCCC M25234T=KCTC 25639T).

Paracoccus onchidii sp. nov., a moderately halophilic bacterium isolated from a marine invertebrate from the South China Sea.

A novel moderately halophilic bacterial strain, designated Z330T, was isolated from the egg of a marine invertebrate of the genus Onchidium collected in the South China Sea. The 16S rRNA gene sequence of strain Z330T exhibited the highest similarity value to that of the type strain Paracoccus fistulariae KCTC 22803T (97.6%), Paracoccus seriniphilus NBRC 100798T (97.6%) and Paracoccus aestuarii DSM 19484T (97.6%). Phylogenomic and 16S rRNA phylogenetic analysis showed that strain Z330T was most closely related to P. seriniphilus NBRC 100798T and P. fistulariae KCTC 22803T. Strain Z330T grew optimally at 28-30 °C, pH 7.0-8.0 with the presence of 5.0-7.0% (w/v) NaCl. In addition, growth of strain Z330T occurred at 0.5-16% NaCl, indicated strain Z330T was a moderately halophilic and halotolerant bacterium of genus Paracoccus. The predominant respiratory quinone in strain Z330T was identified as ubiquinone-10. The major polar lipids of strain Z330T were phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, glycolipid and six unidentified polar lipids. The major fatty acids of strain Z330T was summed feature 8 (C18:1 ω6c and/or C18:1 ω7c). The draft genome sequence of strain Z330T includes 4,084,570 bp in total (N50 = 174,985 bp) with a medium read coverage of 463.6 × and 83 scaffolds. The DNA G + C content of strain Z330T was 60.5%. In silico DNA-DNA hybridization with the four type strains showed 20.5, 22.3, 20.1 and 20.1% relatedness to Paracoccus fistulariae KCTC 22803T, Paracoccus seriniphilus NBRC 100798T, Paracoccus aestuarii DSM 19484T and Paracoccus denitrificans 1A10901T, respectively. And the average nucleotide identity (ANIb) values between strain Z330T and these four type strains were 76.2, 80.0, 75.8 and 73.8%, respectively, lower than the 95-96% threshold value for dividing prokaryotic species. On the basis of the phenotypic, phylogenetic, phylogenomic and chemotaxonomic properties, a novel species of the genus Paracoccus, Paracoccus onchidii sp. nov. is proposed with the type strain Z330T (= KCTC 92727T = MCCC 1K08325T).