Se-p Orbitals Induced "Strong d-d Orbitals Interaction" Enable High Reversibility of Se-Rich ZnSe/MnSe@C Electrode as Excellent Host for Sodium-Ion Storage.

The heterostructure of transition-metal chalcogenides is a promising approach to boost alkali ion storage due to fast charge kinetics and reduction of activation energy. However, cycling performance is a paramount challenge that is suffering from poor reversibility. Herein, it is reported that Se-rich particles can chemically interact with local hexagonal ZnSe/MnSe@C heterostructure environment, leading to effective ions insertion/extraction, enabling high reversibility. Enlightened by theoretical understanding, Se-rich particles endow high intrinsic conductivities in term of low energy barriers (1.32 eV) compared with those without Se-rich particles (1.50 eV) toward the sodiation process. Moreover, p orbitals of Se-rich particles may actively participate and further increase the electronegativity that pushes the Mn d orbitals (dxy and dx2-y2) and donate their electrons to dxz and dyz orbitals, manifesting strong d-d orbitals interaction between ZnSe and MnSe. Such fundamental interaction will adopt a well-stable conducive electronic bridge, eventually, charges are easily transferred from ZnSe to MnSe in the heterostructure during sodiation/desodiation. Therefore, the optimized Se-rich ZnSe/MnSe@C electrode delivered high capacity of 576 mAh g-1 at 0.1 A g-1 after 100 cycles and 384 mAh g-1 at 1 A g-1 after 2500 cycles, respectively. In situ and ex situ measurements further indicate the integrity and reversibility of the electrode materials upon charging/discharging.

Neiella litorisoli sp. nov., an alginate lyase: producing bacterium from South China Sea, and proposal of Echinimonadaceae fam. nov. in the order Alteromonadales.

A Gram-stain-negative, rod-shaped bacterium, designated HB171785T, was isolated from soil sample collected from Qishui Bay, Hainan, China. The strain grew optimally at pH 7-8, 37-40 °C and with NaCl 3-4%. The predominant isoprenoid quinone was found to be Q-8 and the major fatty acids were C16:0, C16:1 ω7c/C16:1 ω6c, C18:1 ω7c/C18:1 ω6c and C12:0 3OH. The polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The size of the draft genome was 4.32 Mbp with G + C content 49.7%. Phylogenetic analysis of 16S rRNA gene sequence indicated that the closest phylogenetically related species were Neiella marina j221T, "Neiella holothuriorum" 126 and Echinimonas agarilytica KMM 6351T with the similarities of 98.2, 96.0 and 95.0%, respectively. The phylogenetic tree based on 16S rRNA gene and phylogenomic tree based on core genome showed that strain HB171785T clustered together with N. marina j221T, with the highest values of average nucleotide identity (82.9%) and digital DNA-DNA hybridization (25.4%). The combined phylogenetic relatedness, phenotypic and genotypic features supported the conclusion that strain HB171785T represents a novel species of the genus Neiella, for which the name Neiella litorisoli sp. nov. is proposed. The type strain is HB171785T (= MCCC 1K04625T = KCTC 82319T). In addition, Echinimonadaceae fam. nov. in the order Alteromonadales was proposed.

Metabacillus arenae sp. nov., isolated from seashore sand.

A Gram-stain-positive, non-motile, rod-shaped, facultatively anaerobic bacterium, designated as IB182487T, was isolated from a seashore sand sample collected from Zhaoshu Island, PR China. Strain IB182487T grew at pH 6.0-10.0 (optimum, pH 8.0), 4-45 °C (optimum, 25-30 °C) and with 0-17 % (w/v) NaCl (optimum, 2-10 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain IB182487T belonged to the genus Metabacillus and was closely related to Metabacillus idriensis SMC 4352-2T, (96.6 %), Metabacillus indicus LMG 22858T (96.5 %), Metabacillus niabensis DSM 17723T (96.3 %) and Metabacillus halosaccharovorans DSM 25387T (96.1 %). Strain IB182487T had meso-diaminopimelic acid as the diagnostic diamino acid in the cell-wall peptidoglycan and contained menaquinone MK-7 as the predominant isoprenoid quinone. Its polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids and three unidentified glycolipids. The major cellular fatty acids of strain IB182487T were iso-C15 : 0 and anteiso-C15 : 0. The whole genome average nucleotide identity and digital DNA-DNA hybridization analysis between the isolate and its closely related type strains demonstrated that the strain significantly differed from other Metabacillus species. The genomic DNA G+C content of strain IB182487T was 37.4 mol%. On the basis of phenotypic and chemotaxonomic properties, phylogenetic relatedness as well as genomic characteristics, strain IB182487T represents a novel species of the genus Metabacillus, for which the name Metabacillus arenae sp. nov. is proposed. The type strain of M. arenae is IB182487T (=MCCC 1K04629T=JCM 34523T).

Polycladospora coralii gen. nov., sp. nov., a novel member of the family Thermoactinomycetaceae isolated from stony coral in the South China Sea.

Two novel filamentous bacteria, designated as IB182353T and IB182357, were isolated from stony coral of the South China Sea. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains IB182353T and IB182357 were closely related to Hazenella coriacea DSM 45707T (with 93.4 and 93.5% similarity, respectively). The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization results showed that the pairwise similarities between isolate IB182353T and the other recognized Thermoactinomycetaceae species were less than 68.9, 60.5 and 21.1 %, respectively. Both strains produced aerial and substrate mycelia, grew optimally at 25-30 °C, pH 8.0-9.0 and with 2-3 % (w/v) NaCl. The cell-wall peptidoglycan type was meso-DAP and the whole-cell hydrolysates contained ribose. The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminophospholipid and three unidentified phospholipids. The genomic DNA G+C content was 39.5 mol%. Strain IB182353T was distinguishable from its related type strains by the contents of two fatty acids, iso-C15 : 0 and iso-C17 : 1 ω10c. Based on polyphasic taxonomic characterization, we propose that strains IB182353T and IB182357 represent a novel genus and species within the family Thermoactinomycetaceae, for which the name Polycladospora coralii gen. nov. sp. nov. is proposed. The type strain is IB182353T (=MCCC 1K04631T=JCM 34206T).

Paenibacillus sabuli sp. nov., isolated from the South China Sea.

A Gram-positive, rod-shaped, motile, spore-forming bacterium, designated strain IB182496T, was isolated from coastal sand of the South China Sea. The strain grew optimally at pH 7.0-9.0, 20-30 °C, and with NaCl 3.0-5.0 %. The predominant menaquinone was MK-7 and the major cellular fatty acids were anteiso-C15 : 0, iso-C16 : 0 and C16 : 0. The polar lipids in the cell wall included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unidentified phospholipids and one unidentified lipid. The comparison of 16S rRNA gene sequences indicated that strain IB182496T was most closely related to 'Paenibacillus sambharensis' SMB1 and Paenibacillus tarimensis SA-7-6T with similarities of 95.7 and 95.5 %, respectively. The whole-genome average nucleotide identity values between strain IB182496T and the two reference strains were 70.8 and 70.5%, and the digital DNA-DNA hybridization values were 18.7 and 18.0 %, respectively. Genomic analyses showed that strain IB182496T presented a genome of 6.22 Mbp with chromosomal G+C content of 60.3 %, and a total of 5261 genes were predicted. The combined phylogenetic relatedness, phenotypic and genotypic features supported the conclusion that strain IB182496T should be considered as representing a novel species of the genus Paenibacillus, for which we propose the name Paenibacillus sabuli sp. nov. with the type strain IB182496T (=MCCC 1K04627T=JCM 34216T).

Paenibacillus arenilitoris sp. nov., isolated from seashore sand and genome mining revealed the biosynthesis potential as antibiotic producer.

Strain IB182493T, a marine, aerobic, Gram-stain-negative and motile bacterium, was isolated from seashore sand of South China Sea. Cells grew optimally at 25-30 °C, pH 7.0-8.0 and with 2-4% NaCl (w/v). Phylogenetic analysis based on 16S rRNA gene sequence comparison revealed that the strain formed a distinct lineage within the genus Paenibacillus, and was most closely related to Paenibacillus harenae DSM 16969 T (similarity 96.6%) and Paenibacillus alkaliterrae DSM 17040 T (similarity 96.1%). The chemotaxonomic characteristics of strain IB182493T included MK-7 as the predominant isoprenoid quinone, anteiso-C15:0 and iso-C16:0 as the major cellular fatty acids and meso-diaminopimelic acid as the diagnostic diaminoacid in cell wall peptidoglycan. The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and two unidentified phospholipids. The DNA G + C content of strain IB182493T was 56.2 %. The values of whole genome average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) between the isolate and the closely related type strains were less than 84.7% and 23.6%, respectively. On the basis of phenotypic and chemotaxonomic properties, phylogenetic distinctiveness and genomic data, we named the strain as Paenibacillus arenilitoris sp. nov. and proposed that strain IB182493T (= MCCC 1K04626T = JCM 34215 T) in the genus Paenibacillus represents a novel species.

Genome Analysis of a Novel Polysaccharide-Degrading Bacterium Paenibacillus algicola and Determination of Alginate Lyases.

Carbohydrate-active enzymes (CAZymes) are an important characteristic of bacteria in marine systems. We herein describe the CAZymes of Paenibacillus algicola HB172198T, a novel type species isolated from brown algae in Qishui Bay, Hainan, China. The genome of strain HB172198T is a 4,475,055 bp circular chromosome with an average GC content of 51.2%. Analysis of the nucleotide sequences of the predicted genes shows that strain HB172198T encodes 191 CAZymes. Abundant putative enzymes involved in the degradation of polysaccharides were identified, such as alginate lyase, agarase, carrageenase, xanthanase, xylanase, amylases, cellulase, chitinase, fucosidase and glucanase. Four of the putative polysaccharide lyases from families 7, 15 and 38 were involved in alginate degradation. The alginate lyases of strain HB172198T exhibited the maximum activity 152 U/mL at 50 °C and pH 8.0, and were relatively stable at pH 7.0 and temperatures lower than 40 °C. The average degree of polymerization (DP) of the sodium alginate oligosaccharide (AOS) degraded by the partially purified alginate lyases remained around 14.2, and the thin layer chromatography (TCL) analysis indicated that it contained DP2-DP8 oligosaccharides. The complete genome sequence of P. algicola HB172198T will enrich our knowledge of the mechanism of polysaccharide lyase production and provide insights into its potential applications in the degradation of polysaccharides such as alginate.

Maribrevibacterium harenarium gen. nov., sp. nov., represented by a marine strain of the family Oceanospirillaceae.

A Gram-stain-negative, non-motile, facultatively anaerobic, short rod-shaped bacterium, designated HB171799T, was isolated from seacoast sandy soil collected at Qishui Bay, Hainan, PR China. The chemotaxonomic analysis revealed that the respiratory quinones were Q-8 and Q-7, and the major cellular fatty acids were summed feature 8 (comprising C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0 and C18 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid and an unidentified lipid. The size of the draft genome was 3.68 Mb with a DNA G+C content of 48.0 mol%. Results of phylogenetic analyses based on 16S rRNA gene and genome sequences showed that the novel isolate belonged to the family Oceanospirillaceae and formed a distinct subcluster at the base of the radiation of the genus Marinomonas. The highest sequence similarity (96.0 %) of the novel isolate was found to the type strains of Marinomonas fungiae JCM 18476T and Marinomonas ostreistagni DSM23425T. The whole genome-based phylogeny and differences in cellular fatty acids and polar lipids readily distinguished strain HB171799T from all the closely related validly published type strains. Strain HB171799T is therefore suggested to represent a novel species of a new genus in the family Oceanospirillaceae, for which the name Maribrevibacterium harenarium gen. nov., sp. nov. is proposed. The type strain is HB171799T (=CGMCC 1.16727T=JCM 33332T).

Mangrovicoccus algicola sp. nov., an alginate lyase - producing marine bacterium.

A Gram-stain-negative, non-motile, ellipsoid bacterium, designated HB182678T, was isolated from brown alga collected from Hainan province, PR China. Growth was observed at 10-50 °C (optimum 37-40 °C), at pH 6-10 (optimum pH 8) and in the presence of 0.5-13% (w/v) NaCl (optimum, 2-4%). The predominant isoprenoid quinone was Q-10 and the major fatty acids were C18 : 1 ω7c, C16 : 0, C18 : 0 and C19 : 0 cyclo ω8c. The polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, an unidentified phospholipid, two unidentified glycolipids and three unidentified aminophospholipids. The size of the draft genome was 4.40 Mbp with G+C content 68.8 mol%. Phylogenetic analysis of 16S rRNA gene sequence indicated that strain HB182678T belonged to the genus Mangrovicoccus, and the closest phylogenetically related species was Mangrovicoccus ximenensis T1lg56T (with the similarity of 96.3%). Whole genome average nucleotide identity (ANI) value between them was 84.3% and in silico DNA-DNA hybridization value was 27.2%. The combined phylogenetic relatedness, phenotypic and genotypic features supported the conclusion that strain HB182678T represents a novel species of the genus Mangrovicoccus, for which the name Mangrovicoccus algicola sp. nov. is proposed. The type strain is HB182678T (=MCCC 1K04624T=KCTC 82318T).

Paenibacillus oceani sp. nov., isolated from surface seawater.

A Gram-stain-positive and motile bacterial strain, designated IB182363T, was isolated from surface seawater of the South China Sea. Cells grew at pH 5.0-9.5 (optimum, pH 7.0-8.0), 20-40 °C (optimum, 30 °C) and with 1-8 % (w/v) NaCl (optimum, 2-4 %). On the basis of 16S rRNA gene sequence analysis, strain IB182363T was affiliated to the genus Paenibacillus and the closest phylogenetically related species was Paenibacillus ginsengarvi DSM18677T with 96.9 % sequence similarity. The values of whole genome average nucleotide identity analysis and digital DNA-DNA hybridization between the isolate and the closely related type strains were less than 86.3 and 25.6 %, respectively. Chemotaxonomic analysis revealed that strain IB182363T possessed meso-diaminopimelic acid in the cell-wall peptidoglycan and contained menaquinone MK-7 as the predominant isoprenoid quinone. The major cellular fatty acids were anteiso-C15 : 0, C16 : 0 and iso-C16 : 0. The polar lipids comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified glycolipid, two unidentified aminolipids, two unidentified phospholipids and four unidentified aminophospholipids. The genomic DNA G+C content was 54.5 mol%. On the basis of the above results, strain IB182363T represents a novel species of the genus Paenibacillus, for which we propose the name Paenibacillus oceani sp. nov. with the type strain IB182363T (=MCCC 1K04630T=JCM 34214T).

Expression and Characterization of a Cold-Adapted Alginate Lyase with Exo/Endo-Type Activity from a Novel Marine Bacterium Alteromonas portus HB161718T.

The alginate lyases have unique advantages in the preparation of alginate oligosaccharides and processing of brown algae. Herein, a gene alg2951 encoding a PL7 family alginate lyase with exo/endo-type activity was cloned from a novel marine bacterium Alteromonas portus HB161718T and then expressed in Escherichia coli. The recombinant Alg2951 in the culture supernatant reached the activity of 63.6 U/mL, with a molecular weight of approximate 60 kDa. Alg2951 exhibited the maximum activity at 25 °C and pH 8.0, was relatively stable at temperatures lower than 30 °C, and showed a special preference to poly-guluronic acid (polyG) as well. Both NaCl and KCl had the most promotion effect on the enzyme activity of Alg2951 at 0.2 M, increasing by 21.6 and 19.1 times, respectively. The TCL (Thin Layer Chromatography) and ESI-MS (Electrospray Ionization Mass Spectrometry) analyses suggested that Alg2951 could catalyze the hydrolysis of sodium alginate to produce monosaccharides and trisaccharides. Furthermore, the enzymatic hydrolysates displayed good antioxidant activity by assays of the scavenging abilities towards radicals (hydroxyl and ABTS+) and the reducing power. Due to its cold-adapted and dual exo/endo-type properties, Alg2951 can be a potential enzymatic tool for industrial production.

Amaricoccus solimangrovi sp. nov., isolated from mangrove soil.

Strain HB172011T was isolated from mangrove soil sampled at the Bamenbay mangrove forest, PR China. Cells were easily recognized under the microscope as cocci that were usually arranged in distinctive tetrads. Results of phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate belongs to the genus Amaricoccus and has 95.6-96.3% 16S rRNA gene sequence similarities to the four Amaricoccus type strains. The strain was aerobic or facultatively anaerobic, Gram-stain-negative and non-motile. Cells were found to grow at 10-40 °C (optimum, 30 °C), pH 6.0-9.0 (optimum, pH 7.0) and with 0-9.0% (w/v) NaCl (optimum, 2-4%). Major fatty acids were feature 8 (C18:1 ω7c and/or C18:1 ω6c), C16:0, C19:0 cyclo ω8c and summed feature 2 (C16:1 iso I and/or C14:0-3 OH). Genome sequencing revealed a genome size of 4.87 Mbp and a DNA G+C content of 69.9 mol %. Based on these data, strain HB172011T represents a novel species of Amaricoccus, for which the name Amaricoccus solimangrovi sp. nov. is proposed. The type strain is HB172011T (=CGMCC 1.16728T=JCM 33334T).

Bacillus caeni sp. nov., isolated from mangrove sediment.

A Gram-variable, aerobic, motile and irregular rod-shaped bacterium, designated HB172195T, was isolated from a mangrove sediment sample collected from Bamen Bay mangrove forest, China. Cells of the strain were oxidase-negative but positive for catalase and nitrate reduction. Strain HB172195T was found to grow at 15-50 °C (optimum, 25-40 °C), pH 5.0-9.0 (optimum, pH 7.0) and in 1.0-11.0 % (w/v) NaCl (optimum, 3-6 %). Chemotaxonomic analysis indicated that the sole respiratory quinone was MK-7 and the cell-wall peptidoglycan was meso-diaminopimelic acid. The predominant cellular fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and C16 : 1ω7c alcohol. The major polar lipids consisted of phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and an unidentified phospholipid. The genomic DNA G+C content was 40.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain was closely related to Bacillus hwajinpoensis SW-72T (96.3%), Bacillus algicola KMM 3737T (96.2 %) and Bacillus haemicentroti JSM 076093T (95.5 %). Based on polyphasic taxonomic characterization, strain HB172195T is considered to represent a novel species, for which the name Bacillus caeni sp. nov. is proposed. The type strain is HB172195T (=CGMCC 1.16730T=JCM 33411T).

Microbulbifer harenosus sp. nov., an alginate-degrading bacterium isolated from coastal sand.

A Gram-stain-negative, aerobic, rod-shaped bacterium with peritrichous flagella, designated strain HB161719T, was isolated from coastal sand collected from Tanmen Port in Hainan, PR China. The isolate was found to grow with 2-11 % (w/v) NaCl, at 15-45 °C and pH 6.0-10.0, with an optima of 2-3 % NaCl, 37 °C and pH 7.0, respectively. Chemotaxonomic analysis showed that Q-8 was detected as the sole respiratory quinone and that iso-C15 : 0 and summed features 3, 8 and 9 were the major cellular fatty acids. The G+C content of the genomic DNA was 58.2 mol%. Analysis of the 16S rRNA gene sequence of the strain showed an affiliation with the genus Microbulbifer, sharing 98.7, 98.4, 97.8 and 97.8 % sequence similarities to the closest relatives of Microbulbifer okinawensis ABABA23T, Microbulbifer pacificus SPO729T, Microbulbifer taiwanensis CC-LN1-12T and Microbulbifer gwangyangensis GY2T, respectively. Low DNA-DNA hybridization values showed that it formed a distinct genomic species. The combined phenotypic and molecular features supported that strain HB161719T represents a novel species of the genus Microbulbifer, for which the name Microbulbifer harenosus sp. nov. is proposed. The type strain is HB161719T (=CGMCC 1.13584T=JCM 32688T).

Alteromonas portus sp. nov., an alginate lyase-excreting marine bacterium.

An alginate lyase-excreting bacterium, designated strain HB161718T, was isolated from coastal sand collected from Tanmen Port in Hainan, PR China. Cells were Gram-stain-negative rods and motile with a single polar flagellum. Its major isoprenoid quinone was ubiquinone 8 (Q-8), and its cellular fatty acid profile mainly consisted of C16 : 1 ω7c and/or C16 : 1 ω6c, C18 : 1 ω6c and/or C18 : 1 ω7c, C16 : 0, C17 : 0 10-methyl and C16 : 0 N alcohol. The G+C content of the genomic DNA was 44.1 mol%. 16S rRNA gene sequence analysis suggested that strain HB161718T belonged to the genus Alteromonas, sharing 99.5, 99.4, 99.2, 98.9 and 98.5 % sequence similarities to its closest relatives, Alteromonas macleodii JCM 20772T, Alteromonas gracilis 9a2T, Alteromonas australica H17T, Alteromonas marina SW-47T and Alteromonas mediterranea DET, respectively. The low values of DNA-DNA hybridization and average nucleotide identity showed that it formed a distinct genomic species. The combined phenotypic and molecular features supported the conclusion that strain HB161718T represents a novel species of the genus Alteromonas, for which the name Alteromonas portus sp. nov. is proposed. The type strain is HB161718T (=CGMCC 1.13585T=JCM 32687T).

Paenibacillus algicola sp. nov., a novel alginate lyase-producing marine bacterium.

A Gram-stain-variable, facultatively anaerobic, endospore-forming, rod-shaped bacterium, designated HB172198T, was isolated from brown alga collected at Qishui Bay, Hainan, PR China. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain HB172198T belonged to the genus Paenibacillus, and the closest phylogenetically related species was Paenibacillus lemnae NBRC 109972T (97.6% similarity). The other 16S rRNA gene sequence similarities were under 97.0%. The whole genome average nucleotide identity value between strain HB172198T and the closest type strain was 75.3% and the in silico DNA-DNA hybridization value was 20.2%. The predominant isoprenoid quinone was menaquinone 7 and the major fatty acids were anteiso-C15:0, C16:0, anteiso-C17:0, iso C16:0 and C16:1 ω11c. The combined phylogenetic relatedness, phenotypic and genotypic features supported the conclusion that strain HB172198T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus algicola sp. nov. is proposed. The type strain is HB172198T (=CGMCC 1.13583T=JCM 32683T).

Pontibacter mangrovi sp. nov., isolated from mangrove sediment.

A Gram-stain-negative, short-rod-shaped and pink-pigmented bacterial strain (HB172049T) was isolated from mangrove sediment. Cells grew at 10-45 °C (optimum, 30 °C), pH 6.0-9.0 (optimum, pH 7.0) and with 0.5-9.0 % (w/v) NaCl (optimum, 2-5 %). Analysis of the 16S rRNA gene sequence revealed that the isolate had highest sequence similarities to Pontibacter mucosus DSM 100162T (96.5 %) and Pontibacter korlensis X14-1T (96.5 %). The values of average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization between the isolate and its close neighbours were, respectively, less than 80.1, 81.7 and 23.2 %. Chemotaxonomic analysis indicated that the sole respiratory quinone was MK-7 and the predominant cellular fatty acids were summed feature 4 and iso-C15 : 0 (42.2 and 24.6 %, respectively). The major polar lipids consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, one unidentified glycolipid, one unidentified phospholipid, one unidentified aminophospholipid and two unidentified polar lipids. The genomic DNA G+C content was 52.6 mol%. Based on polyphasic taxonomic characterization, it is proposed that strain HB172049T belongs to the genus Pontibacter and represents a novel species, for which the name Pontibacter mangrovi sp. nov. is proposed. The type strain is HB172049T (=CGMCC 1.16729T=JCM 33333T).

Characterization, expression, and antimicrobial activity of histones from Japanese flounder Paralichthys olivaceus.

Histone proteins are not only structurally important for chromosomal DNA packaging but also involved in the regulation of gene expression and the immune response of host against pathogens. Japanese flounder (Paralichthys olivaceus) as one of the most important marine flatfish, suffered from widespread outbreaks of diseases, and its immunological functioning remained to be elucidated. In the present study, we reported the expression patterns of four histones (H1, H2A, H3, and H3.3) and functional characterization of the histone H3.3 from flounder. Quantitative real time RT-PCR (RT-qPCR) analysis showed that expression of the four histones occurred in multiple tissues, but their levels of expression were relatively high in immune organs, and inducible in response to pathogens infection. Infection with extracellular and intracellular bacterial pathogens and viral pathogen regulated the expression of histones in a manner that depended on tissue type, pathogen, and infection stage. Specifically, H1 expression was highly induced by intracellular viral pathogens; H2AX and H3 expressions were highly induced by intracellular bacterial pathogen; dissimilarly, H3.3 expression was slightly induced by extracellular bacterial pathogen, but was inhibited by intracellular bacterial and viral pathogens. To further investigate H3.3 function, recombinant H3.3 (rH3.3) was obtained, and in vitro experiments showed rH3.3 possessed the capability of binding to both Gram-negative and Gram-positive bacteria and inhibiting the growth of some target bacteria. Consistently, In vivo results showed that overexpression of H3.3 promoted the host defense against invading pathogenic microorganism and regulated the expressions of several cytokines. These results suggested that flounder histones exhibit different expression patterns in response to the infection of different microbial pathogens, and H3.3 serves as an immune-related protein and plays an important role in antimicrobial immunity of Japanese flounder. Taken together, this study is the first report about the expression profile of different histones upon different kind of pathogens and anti-infectious immunity of H3.3 in teleost, which offered new insights into the immunological function of histones in teleost.

HutZ is required for biofilm formation and contributes to the pathogenicity of Edwardsiella piscicida.

Edwardsiella piscicida is a severe fish pathogen. Haem utilization systems play an important role in bacterial adversity adaptation and pathogenicity. In this study, a speculative haem utilization protein, HutZEp, was characterized in E. piscicida. hutZEp is encoded with two other genes, hutW and hutX, in an operon that is similar to the haem utilization operon hutWXZ identified in V. cholerae. However, protein activity analysis showed that HutZEp is probably not related to hemin utilization. To explore the biological role of HutZEp, a markerless hutZEp in-frame mutant strain, TX01ΔhutZ, was constructed. Deletion of hutZEp did not significantly affect bacterial growth in normal medium, in iron-deficient conditions, or in the presence of haem but significantly retarded bacterial biofilm growth. The expression of known genes related to biofilm growth was not affected by hutZEp deletion, which indicated that HutZEp was probably a novel factor promoting biofilm formation in E. piscicida. Compared to the wild-type TX01, TX01ΔhutZ exhibited markedly compromised tolerance to acid stress and host serum stress. Pathogenicity analysis showed that inactivation of hutZEp significantly impaired the ability of E. piscicida to invade and reproduce in host cells and to infect host tissue. In contrast to TX01, TX01ΔhutZ was defective in blocking host macrophage activation. The expression of hutZEp was directly regulated by the ferric uptake regulator Fur. This study is the first functional characterization of HutZ in a fish pathogen, and these findings suggested that HutZEp is essential for E. piscicida biofilm formation and contributes to host infection.

Thioredoxin H (TrxH) contributes to adversity adaptation and pathogenicity of Edwardsiella piscicida.

Thioredoxins (Trxs) play an important role in defending against oxidative stress and keeping disulfide bonding correct to maintain protein function. Edwardsiella piscicida, a severe fish pathogen, has been shown to encode several thioredoxins including TrxA, TrxC, and TrxH, but their biological roles remain unknown. In this study, we characterized TrxH of E. piscicida (named TrxHEp) and examined its expression and function. TrxHEp is composed of 125 residues and possesses typical thioredoxin H motifs. Expression of trxHEp was upregulated under conditions of oxidative stress, iron starvation, low pH, and during infection of host cells. trxHEp expression was also regulated by ferric uptake regulator (Fur), an important global regulatory of E. piscicida. Compared to the wild type TX01, a markerless trxHEp in-frame mutant strain TX01∆trxH exhibited markedly compromised tolerance of the pathogen to hydrogen peroxide, acid stress, and iron deficiency. Deletion of trxHEp significantly retarded bacterial biofilm growth and decreased resistance against serum killing. Pathogenicity analysis shows that the inactivation of trxHEp significantly impaired the ability of E. piscicida to invade host cells, reproduce in macrophages, and infect host tissues. Introduction of a trans-expressed trxH gene restored the lost virulence of TX01∆trxH. There is likely to be a complex relationship of functional complementation or expression regulation between TrxH and another two thioredoxins, TrxA and TrxC, of E. piscicida. This is the first functional report of TrxH in fish pathogens, and the findings suggest that TrxHEp is essential for coping with adverse circumstances and contributes to host infection of E. piscicida.