High-Level Extracellular Production of a Trisaccharide-Producing Alginate Lyase AlyC7 in Escherichia coli and Its Agricultural Application.

Alginate oligosaccharides (AOS), products of alginate degradation by endotype alginate lyases, possess favorable biological activities and have broad applications. Although many have been reported, alginate lyases with homogeneous AOS products and secretory production by an engineered host are scarce. Herein, the alginate lyase AlyC7 from Vibrio sp. C42 was characterized as a trisaccharide-producing lyase exhibiting high activity and broad substrate specificity. With PelB as the signal peptide and 500 mM glycine as the additive, the extracellular production of AlyC7 in Escherichia coli reached 1122.8 U/mL after 27 h cultivation in Luria-Bertani medium. The yield of trisaccharides from sodium alginate degradation by the produced AlyC7 reached 758.6 mg/g, with a purity of 85.1%. The prepared AOS at 20 µg/mL increased the root length of lettuce, tomato, wheat, and maize by 27.5%, 25.7%, 9.7%, and 11.1%, respectively. This study establishes a robust foundation for the industrial and agricultural applications of AlyC7.

New insights into the origin of buckwheat cultivation in southwestern China from pollen data.

Buckwheat is an important crop which originated in China and spread widely across Eurasia. However, exactly where in China domestication took place remains controversial. Archaeological and palynological records suggest a longer cultivation history of buckwheat in northern China than in southwestern China, but this conflicts with phylogenetic evidence implicating southwestern China as the centre of origin and diversity of buckwheat. We investigate alternative methodologies for inferring the occurrence of buckwheat cultivation and suggest that relative abundance could provide a reliable measure for distinguishing between wild and cultivated buckwheat in both present-day and fossil samples. Approximately 12 800-yr palaeoecological record shows that Fagopyrum pollen occurred only infrequently before the early Holocene. As southwestern China entered the early agricultural period, c. 8000-7000 yr ago, a slight increase in abundance of Fagopyrum pollen was observed. Approximately 4000 yr ago, concurrent with the Pu minority beginning to develop dry-land agriculture, the abundance of Fagopyrum pollen increased significantly, suggesting the cultivation of this crop. Fagopyrum pollen rose to a maximum value c. 1270 yr ago, suggesting an intensification of agricultural activity. These findings fill a gap in the Fagopyrum pollen record in southwestern China and provide new indications that early cultivation may have occurred in this region.

Spartinivicinus marinus sp. nov., isolated from intertidal sediment.

A Gram-stain-negative, aerobic, flagellated, and long rod-shaped bacterium, designated strain SM1973T, was isolated from an intertidal sediment sample collected from the coast of Qingdao, PR China. Strain SM1973T grew at 15-37 °C and with 0-5.5 % NaCl. It reduced nitrate to nitrite and hydrolysed aesculin but did not hydrolyse casein and gelatin. The strain showed the highest 16S rRNA gene sequence similarity (98.2 %) to the type strain of Spartinivicinus ruber. The phylogenetic trees based on the 16S rRNA genes and single-copy orthologous clusters showed that strain SM1973T clustered with S. ruber, forming a separate lineage within the family Zooshikellaceae. The major cellular fatty acids were summed feature 3 (C16 : 1 ω7с and/or C16 : 1 ω6с) and C16 : 0. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The main respiratory quinone was ubiquinone-9. The genomic DNA G+C content of strain SM1973T was 40.4 mol%. Based on the polyphasic evidence presented in this paper, strain SM1973T is considered to represent a novel species within the genus Spartinivicinus, for which the name Spartinivicinus marinus sp. nov. is proposed. The type strain is SM1973T (=MCCC 1K04833T=KCTC 72846T).

Alteromonas oceanisediminis sp. nov., isolated from deep-sea sediment.

A Gram-stain-negative, aerobic and rod-shaped bacterium, designated strain SM 2104T, was isolated from a deep-sea sediment sample collected from the Southwest Indian Ocean. Strain SM 2104T grew at 10-37 °C (optimum at 25 °C), and with 1.0-9.0% (w/v, optimum with 2-4%) NaCl. It hydrolyzed starch, tween 80 and gelatin but did not reduced nitrate to nitrite. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM 2104T was affiliated with the genus Alteromonas, sharing the highest 16S rRNA gene sequence similarities with type strains of Alteromonas flava (97.5%) and Alteromonas facilis (97.4%) and forming a distinct clade together with the two Alteromonas species. The digital DNA-DNA hybridization and average nucleotide identity values between strain SM 2104 T and type strains of Alteromonas flava and Alteromonas facilis were below 14.5%, and 71.0%, respectively. The major fatty acids of strain SM 2104T were summed feature 3 (C16:1ω6c/C16:1ω7c), C16:0 and summed feature 8 (C18:1ω7c/C18:1ω6c). The major polar lipids of strain SM 2104T were phosphatidylethanolamine and phosphatidylglycerol and the only respiratory quinone of strain SM 2104T was ubiquinone-8. The genomic DNA G + C content of strain SM 2104T was 48.0%. On the basis of the phylogenetic, phenotypic, chemotaxonomic and genomic analyses presented in this study, strain SM 2104T is considered to represent a novel species within the genus Alteromonas, for which the name Alteromonas oceansediminis sp. nov. is proposed. The type strain is SM 2104T (= CCTCC AB 2021121T = KCTC 82867T).

Arsukibacterium indicum sp. nov., isolated from deep-sea sediment, and transfer of Rheinheimera tuosuensis and Rheinheimera perlucida to the genus Arsukibacterium as Arsukibacterium tuosuense comb. nov. and Arsukibacterium perlucidum comb. nov.

A Gram-stain-negative, aerobic, flagellated and rod-shaped bacterium, designated strain SM2107T, was isolated from a deep-sea sediment sample collected from the Southwest Indian Ocean. Strain SM2107T grew at 4-40 °C and with 0-10.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed casein, gelatin, chitin and DNA. The phylogenetic trees based on the 16S rRNA genes and single-copy orthologous clusters showed that strain SM2107T, together with Rheinheimera tuosuensis, Rheinheimera perlucida and Arsukibacterium ikkense, formed a separate clade, having the highest similarity to the type strain of Rheinheimera tuosuensis (98.3%). The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol and the major cellular fatty acids were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0, C17 : 1 ω8с and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The only respiratory quinone was Q-8. The genomic DNA G+C content of strain SM2107T was 48.8 %. The digital DNA-DNA hybridization values between strain SM2107T and type strains of Rheinheimera tuosuensis, Rheinheimera perlucida and Arsukibacterium ikkense were 41.16, 37.70 and 31.80 %, while the average amino acid identity values between them were 87.59, 86.76 and 83.64 %, respectively. Based on the polyphasic evidence presented in this study, strain SM2107T was considered to represent a novel species within the genus Arsukibacterium, for which the name Arsukibacterium indicum was proposed. The type strain is SM2107T (=MCCC M24986T=KCTC 82921T). Moreover, the transfer of Rheinheimera tuosuensis and Rheinheimera perlucida to the genus Arsukibacterium as Arsukibacterium tuosuense comb. nov. (type strain TS-T4T=CGMCC 1.12461T=JCM 19264T) and Arsukibacterium perlucidum comb. nov. (type strain BA131T=LMG 23581T=CIP 109200T) is also proposed.

Lack of N-Terminal Segment of the Flagellin Protein Results in the Production of a Shortened Polar Flagellum in the Deep-Sea Sedimentary Bacterium Pseudoalteromonas sp. Strain SM9913.

Bacterial polar flagella, comprised of flagellin, are essential for bacterial motility. Pseudoalteromonas sp. strain SM9913 is a bacterium isolated from deep-sea sediments. Unlike other Pseudoalteromonas strains that have a long polar flagellum, strain SM9913 has an abnormally short polar flagellum. Here, we investigated the underlying reason for the short flagellum and found that a single-base mutation was responsible for the altered flagellar assembly. This mutation leads to the fragmentation of the flagellin gene into two genes, PSM_A2281, encoding the core segment and the C-terminal segment, and PSM_A2282, encoding the N-terminal segment, and only gene PSM_A2281 is involved in the production of the short polar flagellum. When a chimeric gene of PSM_A2281 and PSM_A2282 encoding an intact flagellin, A2281::82, was expressed, a long polar flagellum was produced, indicating that the N-terminal segment of flagellin contributes to the production of a polar flagellum of a normal length. Analyses of the simulated structures of A2281 and A2281::82 and that of the flagellar filament assembled with A2281::82 indicate that due to the lack of two α-helices, the core of the flagellar filament assembled with A2281 is incomplete and is likely too weak to support the stability and movement of a long flagellum. This mutation in strain SM9913 had little effect on its growth and only a small effect on its swimming motility, implying that strain SM9913 can live well with this mutation in natural sedimentary environments. This study provides a better understanding of the assembly and production of bacterial flagella. IMPORTANCE Polar flagella, which are essential organelles for bacterial motility, are comprised of multiple flagellin subunits. A flagellin molecule contains an N-terminal segment, a core segment, and a C-terminal segment. The results of this investigation of the deep-sea sedimentary bacterium Pseudoalteromonas sp. strain SM9913 demonstrate that a single-base mutation in the flagellin gene leads to the production of an incomplete flagellin without the N-terminal segment and that the loss of the N-terminal segment of the flagellin protein results in the production of a shortened polar flagellar filament. Our results shed light on the important function of the N-terminal segment of flagellin in the assembly and stability of bacterial flagellar filament.

Marinifaba aquimaris gen. nov., sp. nov., a novel chitin-degrading gammaproteobacterium in the family Alteromonadaceae isolated from seawater of the Mariana Trench.

A novel Gram-negative, rod-shaped, aerobic, oxidase-positive and catalase-negative bacterium, designated strain SM1970T, was isolated from a seawater sample collected from the Mariana Trench. Strain SM1970T grew at 15-37 oC and with 1-5% (w/v) NaCl. It hydrolyzed colloidal chitin, agar and casein but did not reduce nitrate to nitrite. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain SM1970T formed a distinct lineage close to the genus Catenovulum within the family Alteromonadaceae, sharing the highest sequence similarity (93.6%) with type strain of Catenovulum maritimum but < 93.0% sequence similarity with those of other known species in the class Gammaproteobacteria. The major fatty acids of strain SM1970T were summed feature 3 (C16: 1 ω7c and/or C16: 1 ω6c), C16: 0 and summed feature 8 (C18: 1 ω7c and/or C18: 1 ω6c). The major polar lipids of the strain included phosphatidylethanolamine and phosphatidylglycerol and its main respiratory quinone was ubiquinone 8. The draft genome of strain SM1970T consisted of 77 scaffolds and was 4,172,146 bp in length, containing a complete set of genes for chitin degradation. The average amino acid identity (AAI) values between SM1970T and type strains of known Catenovulum species were 56.6-57.1% while the percentage of conserved proteins (POCP) values between them were 28.5-31.5%. The genomic DNA G + C content of strain SM1970T was 40.1 mol%. On the basis of the polyphasic analysis, strain SM1970T is considered to represent a novel species in a novel genus of the family Alteromonadaceae, for which the name Marinifaba aquimaris is proposed with the type strain being SM1970T (= MCCC 1K04323T = KCTC 72844T).

Potential of Thermolysin-like Protease A69 in Preparation of Bovine Collagen Peptides with Moisture-Retention Ability and Antioxidative Activity.

Bovine bone is rich in collagen and is a good material for collagen peptide preparation. Although thermolysin-like proteases (TLPs) have been applied in different fields, the potential of TLPs in preparing bioactive collagen peptides has rarely been evaluated. Here, we characterized a thermophilic TLP, A69, from a hydrothermal bacterium Anoxybacillus caldiproteolyticus 1A02591, and evaluated its potential in preparing bioactive collagen peptides. A69 showed the highest activity at 60 °C and pH 7.0. We optimized the conditions for bovine bone collagen hydrolysis and set up a process with high hydrolysis efficiency (99.4%) to prepare bovine bone collagen peptides, in which bovine bone collagen was hydrolyzed at 60 °C for 2 h with an enzyme-substrate ratio of 25 U/g. The hydrolysate contained 96.5% peptides that have a broad molecular weight distribution below 10000 Da. The hydrolysate showed good moisture-retention ability and a high hydroxyl radical (•OH) scavenging ratio of 73.2%, suggesting that the prepared collagen peptides have good antioxidative activity. Altogether, these results indicate that the thermophilic TLP A69 has promising potential in the preparation of bioactive collagen peptides, which may have potentials in cosmetics, food and pharmaceutical industries. This study lays a foundation for the high-valued utilization of bovine bone collagen.

Vibrio algicola sp. nov., isolated from the surface of coralline algae.

A Gram-stain-negative, oxidase- and catalase-positive, facultative anaerobic and rod-shaped bacterium, designated strain SM1977T, was isolated from the surface of coralline algae collected from the intertidal zone at Qingdao, PR China. The strain grew at 10-35 °C, pH 4.5-8.5 and with 1-8.5% (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed Tween 20 and DNA. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1977T was affiliated with the genus Vibrio, having the highest sequence similarity (97.6 %) to the type strain of Vibrio casei, followed by those of another five species (95.6-97.6 %) in the Rumoiensis clade of the genus Vibrio. However, the in silico DNA-DNA hybridization (75.3-75.9 %) and average nucleotide identity (21.6-22.8 %) values of SM1977T against these close relatives were all below the corresponding thresholds to discriminate bacterial species. The major fatty acids were summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), C16:0 and summed feature 8 (C18:1 ω6c and /or C18:1 ω7c). The predominant polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The sole respiratory quinone was Q-8. The genomic DNA G+C content of strain SM1977T, determined from the obtained whole genomic sequence, was 42.3 mol%. On the basis of the polyphasic results obtained in this study, strain SM1977T is considered to represent a novel species within the genus Vibrio, for which the name Vibrio algicola sp. nov. is proposed. The type strain is SM1977T (=MCCC 1K04351T=KCTC 72847T).

Marinomonas profundi sp. nov., isolated from deep seawater of the Mariana Trench.

A Gram-stain-negative, aerobic, polarly flagellated, straight or curved rod-shaped bacterium, designated strain M1K-6T, was isolated from deep seawater samples collected from the Mariana Trench. The strain grew at -4 to 37 °C (optimum, 25-30 °C), at pH 5.5-10.0 (optimum, pH 7.0) and with 0.5-14.0  % (w/v) NaCl (optimum, 2.0 %). It did not reduce nitrate to nitrite nor hydrolyse gelatin or starch. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain M1K-6T was affiliated with the genus Marinomonas, sharing 93.1-97.0  % sequence similarity with the type strains of recognized Marinomonas species. The major cellular fatty acids were summed feature 3 (C16 : 1 ω6c/C16 : 1 ω7c), summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), C16 : 0, C10 : 0 3-OH and C18 : 0. The predominant respiratory quinone was ubiquinone-8. Polar lipids of strain M1K-6T included phosphatidylethanolamine, phosphatidylglycerol and two unidentified lipids. The genomic G+C content of strain M1K-6T was 46.0 mol%. Based on data from the present polyphasic study, strain M1K-6T was considered to represent a novel species within the genus Marinomonas, for which the name Marinomonas profundi sp. nov. is proposed. The type strain is M1K-6T (=KCTC 72501T=MCCC 1K03890T).

Antarcticimicrobium sediminis gen. nov., sp. nov., isolated from Antarctic intertidal sediment, transfer of Ruegeria lutea to Antarcticimicrobium gen. nov. as Antarcticimicrobium luteum comb. nov.

A Gram-stain-negative, aerobic, non-flagellated and rod- or ovoid-shaped bacterium, designated as strain S4J41T, was isolated from Antarctic intertidal sediment. The isolate grew at 0-37 °C and with 0.5-10 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed Tween 80 and gelatin. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain S4J41T constituted a distinct phylogenetic line within the family Rhodobacteraceae and was closely related with some species in the genera Ruegeria, Phaeobacter, Pseudopuniceibacterium, Sulfitobacter, Puniceibacterium and Poseidonocella with 98.6-95.7 % 16S rRNA gene sequence similarities. The major cellular fatty acids were C16 : 0, summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and C18 : 0 and the major polar lipids were phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, phosphatidylethanolamine and one unidentified aminolipid. The sole respiratory quinone was Q-10. The genomic DNA G+C content of strain S4J41T was 60.3 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data obtained in this study, strain S4J41T is considered to represent a novel species in a new genus within the family Rhodobacteraceae, for which the name Antarcticimicrobium sediminis gen. nov., sp. nov. is proposed. The type strain is S4J41T (=MCCC 1K03508T=KCTC 62793T). Moreover, the transfer of Ruegeria lutea Kim et al. 2019 to Antarcticimicrobium gen. nov. as Antarcticimicrobium luteum comb. nov. (type strain 318-1T=JCM 30927T=KCTC 72105T) is also proposed.

Pelagovum pacificum gen. nov., sp. nov., a novel member of the family Rhodobacteraceae isolated from surface seawater of the Mariana Trench.

A Gram-stain-negative, aerobic, ovoid-rod-shaped bacterium, designated strain SM1903T, was isolated from surface seawater of the Mariana Trench. The strain grew at 15-37 °C (optimum, 35 °C) and with 1-15 % (optimum, 4 %) NaCl. It hydrolysed aesculin but did not reduce nitrate to nitrite and hydrolyse Tween 80. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain SM1903T formed a separate lineage within the family Rhodobacteraceae, sharing the highest 16S rRNA gene sequence similarity with type strains of Pseudooceanicola antarcticus (95.7 %) and Roseisalinus antarcticus (95.7 %). In phylogenetic trees based on single-copy OCs and whole proteins sequences, strain SM1903T fell within a sub-cluster encompassed by Oceanicola granulosus, Roseisalinus antarcticus and Histidinibacterium lentulum and formed a branch adjacent to Oceanicola granulosus. The major cellular fatty acids were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0 and 11-methyl-C18 : 1 ω7c. The polar lipids mainly comprised phosphatidylglycerol, phosphatidylcholine, one unidentified lipid, one unidentified aminolipid, and one unidentified glycolipid. The solo respiratory quinone was ubiquinone-10. The genomic DNA G+C content of strain SM1903T was 66.0 mol%. Based on the results of phenotypic, chemotaxonomic, and phylogenetic characterization for strain SM1903T, it is considered to represent a novel species of a novel genus in the family Rhodobacteraceae, for which the name Pelagovum pacificum gen. nov., sp. nov. is proposed. The type strain is SM1903T (=MCCC 1K03608T=KCTC 72046T).

Shewanella polaris sp. nov., a psychrotolerant bacterium isolated from Arctic brown algae.

A Gram-stain-negative, facultatively anaerobic, flagellated and rod-shaped bacterium, designated strain SM1901T, was isolated from a brown algal sample collected from Kings Bay, Svalbard, Arctic. Strain SM1901T grew at -4‒30 °C and with 0-7.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed DNA and Tween 80. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SM1901T was affiliated with the genus Shewanella, showing the highest sequence similarity to the type strain of Shewanella litoralis (97.5%), followed by those of Shewanella vesiculosa, Shewanella livingstonensis and Shewanella saliphila (97.3 % for all three). The major cellular fatty acids were summed feature 3 (C16 : 1 ω7с and/or C16 : 1 ω6с), C16 : 0, C18 : 0, iso-C15 : 0 and C17 : 1 ω8с and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinones were ubiquinones Q-7, Q-8, menaquinones MK-7(H) and MK-8. The genome of strain SM1901T was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901T was 40.5 mol%. Based on the polyphasic evidence presented in this paper, strain SM1901T was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar Shewanella species, within the genus Shewanella, for which the name Shewanella polaris sp. nov. is proposed. The type strain is SM1901T (=KCTC 72047T=MCCC 1K03585T).

Fluviibacterium aquatile gen. nov., sp. nov., isolated from estuary sediment.

A Gram-negative, aerobic, non-flagellated and ovoid- or rod-shaped bacterium, designated strain SM1902T, was isolated from the sediment sampled at the Jia River estuary, Yantai, PR China. The strain grew at 10-37 °C (optimum, 25-30 °C), pH 6.0-10.0 (pH 7.0) and with 0.5-13.0 % (w/v) NaCl (2.5%). It reduced nitrate to nitrite, but did not produce bacteriochlorophyll a. The results of phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1902T constituted a separated lineage within the family Rhodobacteraceae and was closely related to Meridianimarinicoccus roseus TG-679T and Phycocomes zhengii LMIT002T with 96.1 and 94.3 % 16S rRNA gene sequence similarities, respectively. The predominant cellular fatty acid was summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid and an unidentified lipid. The sole respiratory quinone was ubiquinone-10. The in silico DNA-DNA hybridization values between strain SM1902T and Meridianimarinicoccus roseus TG-679T and Phycocomes zhengii LMIT002T were 19.6 and 19.5 %, respectively; and the average nucleotide identity values between them were 76.1 and 74.2 %, respectively. The genomic DNA G+C content of strain SM1902T was 58.2 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data obtained in this study, strain SM1902T is considered to represent a novel species in a new genus within the family Rhodobacteraceae, for which the name Fluviibacterium aquatile gen. nov., sp. nov. is proposed. The type strain is SM1902T (=KCTC 72045T=MCCC 1K03596T=CCTCC AB 2018346T).

Significant Bacterial Distance-Decay Relationship in Continuous, Well-Connected Southern Ocean Surface Water.

Recently, an increasing number of studies have focused on the biogeographic distribution of marine microorganisms. However, the extent to which geographic distance can affect marine microbial communities is still unclear, especially for the microbial communities in well-connected surface seawaters. In this study, the bacterial community compositions of 21 surface seawater samples, that were distributed over a distance of 7800 km, were surveyed to investigate how bacterial community similarity changes with increasing geographical distance. Proteobacteria and Bacteroidetes were the dominant bacterial phyla, with Proteobacteria accounting for 52.6-92.5% and Bacteroidetes comprising 3.5-46.9% of the bacterial communities. A significant bacterial distance-decay relationship was observed in the well-connected Southern Ocean surface seawater. The number of pairwise shared operational taxonomic units (OTUs), and community similarities tended to decrease with increasing geographic distance. Calculation of the similarity indices with all, abundant or rare OTUs did not affect the observed distance-decay relationship. Spatial distance can largely explain the observed bacterial community variation. This study shows that even in well-connected surface waters, bacterial distance-decay patterns can be found as long as the geographical distance is great enough. The biogeographic patterns should then be present for marine microorganisms considering the large size and complexity of the marine ecosystem.

Improvement of the production of an Arctic bacterial exopolysaccharide with protective effect on human skin cells against UV-induced oxidative stress.

Although microbial exopolysaccharides (EPSs) are applied in different fields, no EPS has been used to protect human skin cells against UV-induced oxidative stress. The EPS produced by the Arctic bacterium Polaribacter sp. SM1127 has high moisture-retention ability and antioxidant activity, suggesting its good industrial potentials. In this study, we improved the EPS production of SM1127 and evaluated its protective effect on human dermal fibroblasts (HDFs) against UV-induced oxidative stress. With glucose as carbon source, the EPS yield was increased from 2.11 to 6.12 g/L by optimizing the fermentation conditions using response surface methodology. To lower the fermentation cost and decrease corrosive speed in stainless steel tanks, whole sugar, whose price is only 8% of that of glucose, was used to replace glucose and NaCl concentration was reduced to 4 g/L in the medium. With the optimized conditions, fed-batch fermentation in a 5-L bioreactor was conducted, and the EPS production reached 19.25 g/L, which represents the highest one reported for a polar microorganism. Moreover, SM1127 EPS could maintain the cell viability and integrity of HDFs under UV-B radiation, probably via decreasing intracellular reactive oxygen species level and increasing intracellular glutathione content and superoxide dismutase activity. Therefore, SM1127 EPS has significant protective effect on HDFs against UV-induced oxidative stress, suggesting its potential to be used in preventing photoaging and photocarcinogenesis. Altogether, this study lays a good foundation for the industrialization of SM1127 EPS, which has promising potential to be used in cosmetics and medical fields.

Pedobacter indicus sp. nov., isolated from deep-sea sediment.

A Gram-stain negative, aerobic, non-flagellated, rod-shaped bacterium, designated strain SM1810T, was isolated from deep-sea sediment collected from the Southwest Indian Ocean. Strain SM1810T grows at 15-40 °C (optimum, 28 °C), at pH 5.0-9.0 (optimum, pH 6.0-7.0) and with 0-8% (w/v) NaCl (optimum, 1.5%). Phylogenetic analysis of 16S rRNA gene sequences revealed that strain SM1810T is affiliated with the genus Pedobacter, sharing high sequence similarity (95.8%) with the type strain of Pedobacter bauzanensis. The major fatty acids of strain SM1810T are iso-C15:0, summed feature 3 (C16:1ω7c and/or C16:1ω6c) and iso-C17:0 3OH. The predominant respiratory quinone is MK-7. The polar lipids are phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified phospholipid and eight unidentified lipids. The genomic DNA G + C content of strain SM1810T was determined to be 40.8 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data obtained in this study, strain SM1810T is concluded to represent a novel species of the genus Pedobacter, for which the name Pedobacter indicus sp. nov. is proposed. The type strain is SM1810T (KCTC 62798T = CCTCC AB 2018198T).

Promotion of Wound Healing and Prevention of Frostbite Injury in Rat Skin by Exopolysaccharide from the Arctic Marine Bacterium Polaribacter sp. SM1127.

Many marine microorganisms synthesize exopolysaccharides (EPSs), and some of these EPSs have been reported to have potential in different fields. However, the pharmaceutical potentials of marine EPSs are rarely reported. The EPS secreted by the Artic marine bacterium Polaribacter sp. SM1127 has good antioxidant activity, outstanding moisture-retention ability, and considerable protective property on human dermal fibroblasts (HDFs) at low temperature. Here, the effects of SM1127 EPS on skin wound healing and frostbite injury prevention were studied. Scratch wound assay showed that SM1127 EPS could stimulate the migration of HDFs. In the full-thickness cutaneous wound experiment of Sprague-Dawley (SD) rats, SM1127 EPS increased the wound healing rate and stimulated tissue repair detected by macroscopic observation and histologic examination, showing the ability of SM1127 EPS to promote skin wound healing. In the skin frostbite experiment of SD rats, pretreatment of rat skin with SM1127 EPS increased the rate of frostbite wound healing and promoted the repair of the injured skin significantly, indicating the good effect of SM1127 EPS on frostbite injury prevention. These results suggest the promising potential of SM1127 EPS in the pharmaceutical area to promote skin wound healing and prevent frostbite injury.

Enhancing peptaibols production in the biocontrol fungus Trichoderma longibrachiatum SMF2 by elimination of a putative glucose sensor.

Trichoderma spp. are main producers of peptide antibiotics known as peptaibols. While peptaibols have been shown to possess a range of biological activities, molecular understanding of the regulation of their production is largely unclear, which hampers the production improvement through genetic engineering. Here, we demonstrated that the orthologue of glucose sensors in the outstanding biocontrol fungus Trichoderma longibrachiatum SMF2, TlSTP1, participates in the regulation of peptaibols production. Deletion of Tlstp1 markedly impaired hyphal growth and conidiation, but significantly increased peptaibols yield by 5-fold for Trichokonins A and 2.6-fold for Trichokonins B. Quantitative real-time polymerase chain reaction analyses showed that the increased peptaibols production occurs at the transcriptional levels of the two nonribosomal peptide synthetase encoding genes, tlx1 and tlx2. Transcriptome analyses of the wild type and the Tlstp1 mutant strains indicated that TlSTP1 exerts a regulatory effect on a set of genes that are involved in a number of metabolic and cellular processes, including synthesis of several other secondary metabolites. These results suggest an important role of TlSTP1 in the regulation of vegetative growth and peptaibols production in T. longibrachiatum SMF2 and provide insights into construction of peptaibol-hyperproducing strains through genetic engineering.

Poseidonibacter antarcticus sp. nov., isolated from Antarctic intertidal sediment.

A Gram-reaction-negative, aerobic, flagellated and coccoid-shaped bacterial strain, designated SM1702T, was isolated from Antarctic intertidal sediment collected off Ardely Island, West Antarctica. The strain grew at 0-30 °C and with 0.5-5.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences and single-copy orthologous clusters both showed that strain SM1702T, together with Poseidonibacter lekithochrous, occupied an independent phylogenetic branch, sharing the highest 16S rRNA gene sequence similarity with type strain of the latter (95.6 %). The major fatty acids were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16 : 0, and summed feature 2 (C14 : 0 3-OH and/or iso-C16 : 1 I). Polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The genomic DNA G+C content of strain SM1702T was 27.1 mol%. Based on the results of the polyphasic characterisation for strain SM1702T, it is identified as the representative of a novel species of Poseidonibacter, for which the name Poseidonibacter antarcticus sp. nov. is proposed. The type strain of Poseidonibacter antarcticus is SM1702T (=MCCC 1K03471T=KCTC 62796T).