Mesonia profundi sp. nov., isolated from deep-sea sediment of the Mariana Trench.

A Gram-stain-negative, aerobic, rod-shaped, non-flagellated, non-gliding bacterial strain, designated MT50T, was isolated from a deep-sea sediment sample collected from the Mariana Trench. Optimal growth of strain MT50T was observed at 25 °C, pH 7.0-7.5 and in the presence of 3-5 % (w/v) NaCl. The strain was positive for oxidase and catalase. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain MT50T is affiliated with the genus Mesonia, showing the highest sequence similarity (98.5 %) to the type strain of Mesonia ostreae. The digital DNA-DNA hybridization and average nucleotide identity values between strain MT50T and four closely related type strains of known Mesonia species (14.1-54.8 % and 72.7-86.8 %, respectively) were all below the threshold values to discriminate bacterial species, indicating that strain MT50T is affiliated with a novel species within the genus. The genomic G+C content deduced from the genome of strain MT50T was 36.2 mol%. The major fatty acids of strain MT50T were iso-C15 : 0, iso-C17 : 0 3-OH and anteiso-C15 : 0. The predominant respiratory quinone of the strain was MK-6. The polar lipids of strain MT50T included phosphatidylethanolamine and two unidentified lipids. Based on the polyphasic data presented in this study, strain MT50T represents a novel species of the genus Mesonia, for which the name Mesonia profundi sp. nov. is proposed. The type strain is MT50T (=MCCC 1K07833T=KCTC 92380T).

Ecological function and interaction of different bacterial groups during alginate processing in coastal seawater community.

The degradation of high molecular weight organic matter (HMWOM) is a core process of oceanic carbon cycle, which is determined by the activity of microbial communities harboring hundreds of different species. Illustrating the active microbes and their interactions during HMWOM processing can provide key information for revealing the relationship between community composition and its ecological functions. In this study, the genomic and transcriptional responses of microbial communities to the availability of alginate, an abundant HMWOM in coastal ecosystem, were elucidated. The main degraders transcribing alginate lyase (Aly) genes came from genera Alteromonas, Psychrosphaera and Colwellia. Meanwhile, some strains, mainly from the Rhodobacteraceae family, did not transcribe Aly gene but could utilize monosaccharides to grow. The co-culture experiment showed that the activity of Aly-producing strain could promote the growth of Aly-non-producing strain when alginate was the sole carbon source. Interestingly, this interaction did not reduce the alginate degradation rate, possibly due to the easily degradable nature of alginate. This study can improve our understanding of the relationship between microbial community activity and alginate metabolism function as well as further manipulation of microbial community structure for alginate processing.

SAR92 clade bacteria are potentially important DMSP degraders and sources of climate-active gases in marine environments.

Dimethylsulfoniopropionate (DMSP) is one of Earth's most abundant organosulfur molecules, which can be catabolized by marine bacteria to release climate-active gases through the cleavage and/or demethylation pathways. The marine SAR92 clade is an abundant oligotrophic group of Gammaproteobacteria in coastal seawater, but their ability to catabolize DMSP is untested. Three SAR92 clade strains isolated from coastal seawater in this study and the SAR92 representative strain HTCC2207 were all shown to catabolize DMSP as a carbon source. All the SAR92 clade strains exhibited DMSP lyase activity producing dimethylsulfide (DMS) and their genomes encoded a ratified DddD DMSP lyase. In contrast, only HTCC2207 and two isolated strains contained the DMSP demethylase dmdA gene and potentially simultaneously demethylated and cleaved DMSP to produce methanethiol (MeSH) and DMS. In SAR92 clade strains with dddD and dmdA, transcription of these genes was inducible by DMSP substrate. Bioinformatic analysis indicated that SAR92 clade bacteria containing and transcribing DddD and DmdA were widely distributed in global oceans, especially in polar regions. This study highlights the SAR92 clade of oligotrophic bacteria as potentially important catabolizers of DMSP and sources of the climate-active gases MeSH and DMS in marine environments, particularly in polar regions.IMPORTANCECatabolism of dimethylsulfoniopropionate (DMSP) by marine bacteria has important impacts on the global sulfur cycle and climate. However, whether and how members of most oligotrophic bacterial groups participate in DMSP metabolism in marine environments remains largely unknown. In this study, by characterizing culturable strains, we have revealed that bacteria of the SAR92 clade, an abundant oligotrophic group of Gammaproteobacteria in coastal seawater, can catabolize DMSP through the DMSP lyase DddD-mediated cleavage pathway and/or the DMSP demethylase DmdA-mediated demethylation pathway to produce climate-active gases dimethylsulfide and methanethiol. Additionally, we found that SAR92 clade bacteria capable of catabolizing DMSP are widely distributed in global oceans. These results indicate that SAR92 clade bacteria are potentially important DMSP degraders and sources of climate-active gases in marine environments that have been overlooked, contributing to a better understanding of the roles and mechanisms of the oligotrophic bacteria in oceanic DMSP degradation.

Cost-effective production of alginate oligosaccharides from Laminaria japonica roots by Pseudoalteromonas agarivorans A3.

BACKGROUND: Alginate oligosaccharides (AOs) are the degradation products of alginate, a natural polysaccharide abundant in brown algae. AOs generated by enzymatic hydrolysis have diverse bioactivities and show broad application potentials. AOs production via enzymolysis is now generally with sodium alginate as the raw material, which is chemically extracted from brown algae. In contrast, AOs production by direct degradation of brown algae is more advantageous on account of its cost reduction and is more eco-friendly. However, there have been only a few attempts reported in AOs production from direct degradation of brown algae. RESULTS: In this study, an efficient Laminaria japonica-decomposing strain Pseudoalteromonas agarivorans A3 was screened. Based on the secretome and mass spectrum analyses, strain A3 showed the potential as a cell factory for AOs production by secreting alginate lyases to directly degrade L. japonica. By using the L. japonica roots, which are normally discarded in the food industry, as the raw material for both fermentation and enzymatic hydrolysis, AOs were produced by the fermentation broth supernatant of strain A3 after optimization of the alginate lyase production and hydrolysis parameters. The generated AOs mainly ranged from dimers to tetramers, among which trimers and tetramers were predominant. The degradation efficiency of the roots reached 54.58%, the AOs production was 33.11%, and the AOs purity was 85.03%. CONCLUSION: An efficient, cost-effective and green process for AOs production directly from the underutilized L. japonica roots by using strain A3 was set up, which differed from the reported processes in terms of the substrate and strain used for fermentation and the AOs composition. This study provides a promising platform for scalable production of AOs, which may have application potentials in industry and agriculture.

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).

Salinimicrobium profundisediminis sp. nov., isolated from deep-sea sediment of the Mariana Trench.

A Gram-stain-negative, aerobic, rod-shaped, non-gliding bacterial strain, designated as MT39T, was isolated from a deep-sea sediment sample collected from the Mariana Trench. Strain MT39T grew optimally at 35°C and pH 7.0, and could tolerate up to 10% (w/v) NaCl. The strain was positive for catalase and negative for oxidase. The genome of strain MT39T was 4 033 307 bp, with a 41.1 mol % genomic G+C content and 3514 coding sequences. Phylogenetic analysis based on 16S rRNA gene sequences placed strain MT39T within the genus Salinimicrobium, showing the highest 16S rRNA gene sequence similarity to Salinimicrobium terrea CGMCC 1.6308T (98.1%). The average nucleotide identity and in silico DNA-DNA hybridization values between strain MT39T and the type strains of seven Salinimicrobium species were all less than the threshold values to discriminate bacterial species, indicating that strain MT39T is affiliated with a novel species within the genus. The major cellular fatty acids of strain MT39T were iso-C15 : 0, anteiso-C15 : 0 and iso-C17 : 0 3-OH. Polar lipids of strain MT39T included phosphatidylethanolamine, one unidentified aminolipid and four unidentified lipids. Menaquinone-6 was the only respiratory quinone in strain MT39T. On the basis of the polyphasic data present in this study, strain MT39T represents a novel species of the genus Salinimicrobium, for which the name Salinimicrobium profundisediminis sp. nov. is proposed, with type strain being MT39T (=MCCC 1K07832T=KCTC 92381T).

Gilvimarinus xylanilyticus sp. nov., a novel 1,3-xylanase-secreting bacterium isolated from a marine green alga.

1,3-xylan, an important organic carbon in the ocean, is peculiar to marine algae. 1,3-xylanase-secreting bacteria and their extracellular 1,3-xylanases play pivotal roles in the degradation and biomass conversion of 1,3-xylan. However, only a few 1,3-xylanase-secreting bacteria and 1,3-xylanases have been reported. Here, we identified a novel marine bacterium capable of secreting 1,3-xylanases, designated as strain HB14T. Phylogenetic analysis revealed that strain HB14T clustered tightly with known species of the genus Gilvimarinus, showing the highest 16S rRNA gene sequence similarity (97.7%) with the type strain of Gilvimarinus chinensis. Based on phylogenetic, genomic, chemotaxonomic and phenotypic studies, strain HB14T was classified as a representative of a novel species in the genus Gilvimarinus, for which the name Gilvimarinus xylanilyticus sp. nov. was proposed. The type strain is HB14T (=CCTCC AB 2022109T = KCTC 92379T). Four 1,3-xylanases secreted by strain HB14T were identified based on genome and secretome analyses, and the two (Xyn65 and Xyn80) with relatively higher abundance in secretome were successfully expressed in Escherichia coli and biochemically characterized. They showed the highest activity at pH 6.0-7.0 and 40°C and released mainly 1,3-xylobiose and 1,3-xylotriose from 1,3-xylan. These data suggest that strain HB14T acts as a player in marine 1,3-xylan degradation and recycling and that its extracellular 1,3-xylanases may have a good potential in 1,3-xylooligosaccharides preparation.

Diaminopimelic Acid Metabolism by Pseudomonadota in the Ocean.

Diaminopimelic acid (DAP) is a unique component of the cell wall of Gram-negative bacteria. It is also an important component of organic matter and is widely utilized by microbes in the world's oceans. However, neither DAP concentrations nor marine DAP-utilizing microbes have been investigated. Here, DAP concentrations in seawater were measured and the diversity of marine DAP-utilizing bacteria and the mechanisms for their DAP metabolism were investigated. Free DAP concentrations in seawater, from surface to a 5,000 m depth, were found to be between 0.61 µM and 0.96 µM in the western Pacific Ocean. DAP-utilizing bacteria from 20 families in 4 phyla were recovered from the western Pacific seawater and 14 strains were further isolated, in which Pseudomonadota bacteria were dominant. Based on genomic and transcriptomic analyses combined with gene deletion and in vitro activity detection, DAP decarboxylase (LysA), which catalyzes the decarboxylation of DAP to form lysine, was found to be a key and specific enzyme involved in DAP metabolism in the isolated Pseudomonadota strains. Interrogation of the Tara Oceans database found that most LysA-like sequences (92%) are from Pseudomonadota, which are widely distributed in multiple habitats. This study provides an insight into DAP metabolism by marine bacteria in the ocean and contributes to our understanding of the mineralization and recycling of DAP by marine bacteria. IMPORTANCE DAP is a unique component of peptidoglycan in Gram-negative bacterial cell walls. Due to the large number of marine Gram-negative bacteria, DAP is an important component of marine organic matter. However, it remains unclear how DAP is metabolized by marine microbes. This study investigated marine DAP-utilizing bacteria by cultivation and bioinformational analysis and examined the mechanism of DAP metabolism used by marine bacteria. The results demonstrate that Pseudomonadota bacteria are likely to be an important DAP-utilizing group in the ocean and that DAP decarboxylase is a key enzyme involved in DAP metabolism. This study also sheds light on the mineralization and recycling of DAP driven by bacteria.

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.

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).

Mechanistic Insight into the Fragmentation of Type I Collagen Fibers into Peptides and Amino Acids by a Vibrio Collagenase.

Vibrio collagenases of the M9A subfamily are closely related to Vibrio pathogenesis for their role in collagen degradation during host invasion. Although some Vibrio collagenases have been characterized, the collagen degradation mechanism of Vibrio collagenase is still largely unknown. Here, an M9A collagenase, VP397, from marine Vibrio pomeroyi strain 12613 was characterized, and its fragmentation pattern on insoluble type I collagen fibers was studied. VP397 is a typical Vibrio collagenase composed of a catalytic module featuring a peptidase M9N domain and a peptidase M9 domain and two accessory bacterial prepeptidase C-terminal domains (PPC domains). It can hydrolyze various collagenous substrates, including fish collagen, mammalian collagens of types I to V, triple-helical peptide [(POG)10]3, gelatin, and 4-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-o-Arg (Pz-peptide). Atomic force microscopy (AFM) observation and biochemical analyses revealed that VP397 first assaults the C-telopeptide region to dismantle the compact structure of collagen and dissociate tropocollagen fragments, which are further digested into peptides and amino acids by VP397 mainly at the Y-Gly bonds in the repeating Gly-X-Y triplets. In addition, domain deletion mutagenesis showed that the catalytic module of VP397 alone is capable of hydrolyzing type I collagen fibers and that its C-terminal PPC2 domain functions as a collagen-binding domain during collagenolysis. Based on our results, a model for the collagenolytic mechanism of VP397 is proposed. This study sheds light on the mechanism of collagen degradation by Vibrio collagenase, offering a better understanding of the pathogenesis of Vibrio and helping in developing the potential applications of Vibrio collagenase in industrial and medical areas. IMPORTANCE Many Vibrio species are pathogens and cause serious diseases in humans and aquatic animals. The collagenases produced by pathogenic Vibrio species have been regarded as important virulence factors, which occasionally exhibit direct pathogenicity to the infected host or facilitate other toxins' diffusion through the digestion of host collagen. However, our knowledge concerning the collagen degradation mechanism of Vibrio collagenase is still limited. This study reveals the degradation strategy of Vibrio collagenase VP397 on type I collagen. VP397 binds on collagen fibrils via its C-terminal PPC2 domain, and its catalytic module first assaults the C-telopeptide region and then attacks the Y-Gly bonds in the dissociated tropocollagen fragments to release peptides and amino acids. This study offers new knowledge regarding the collagenolytic mechanism of Vibrio collagenase, which is helpful for better understanding the role of collagenase in Vibrio pathogenesis and for developing its industrial and medical applications.

A Novel Alginate Lyase: Identification, Characterization, and Potential Application in Alginate Trisaccharide Preparation.

Alginate oligosaccharides (AOS) have many biological activities and significant applications in prebiotics, nutritional supplements, and plant growth development. Alginate lyases have unique advantages in the preparation of AOS. However, only a limited number of alginate lyases have been so far reported to have potentials in the preparation of AOS with specific degrees of polymerization. Here, an alginate-degrading strain Pseudoalteromonasarctica M9 was isolated from Sargassum, and five alginate lyases were predicted in its genome. These putative alginate lyases were expressed and their degradation products towards sodium alginate were analyzed. Among them, AlyM2 mainly generated trisaccharides, which accounted for 79.9% in the products. AlyM2 is a PL6 lyase with low sequence identity (≤28.3%) to the characterized alginate lyases and may adopt a distinct catalytic mechanism from the other PL6 alginate lyases based on sequence alignment. AlyM2 is a bifunctional endotype lyase, exhibiting the highest activity at 30 °C, pH 8.0, and 0.5 M NaCl. AlyM2 predominantly produces trisaccharides from homopolymeric M block (PM), homopolymeric G block (PG), or sodium alginate, with a trisaccharide production of 588.4 mg/g from sodium alginate, indicating its promising potential in preparing trisaccharides from these polysaccharides.

Characterization of the Trimethylamine N-Oxide Transporter From Pelagibacter Strain HTCC1062 Reveals Its Oligotrophic Niche Adaption.

Trimethylamine N-oxide (TMAO), which was detected at nanomolar concentrations in surface seawaters, is an important carbon, nitrogen and/or energy source for marine bacteria. It can be metabolized by marine bacteria into volatile methylated amines, the second largest source of nitrogen after N2 gas in the oceans. The SAR11 bacteria are the most abundant oligotrophic plankton in the oceans, which represents approximately 30% of the bacterial cells in marine surface waters. Genomic analysis suggested that most SAR11 bacteria possess an ATP-binding cassette transporter TmoXWV that may be responsible for importing TMAO. However, it was still unclear whether SAR11 bacteria can utilize TMAO as the sole nitrogen source and how they import TMAO. Here, our results showed that Pelagibacter strain HTCC1062, a SAR11 bacterium, can grow with TMAO as the sole nitrogen source. TmoXWV from strain HTCC1062 (TmoXWV1062) was verified to be a functional TMAO importer. Furthermore, TmoX1062, the periplasmic substrate binding protein of TmoXWV1062, was shown to have high binding affinities toward TMAO at 4°C (K d = 920 nM), 10°C (K d = 500 nM) and 25°C (K d = 520 nM). The high TMAO binding affinity and strong temperature adaptability of TmoX1062 reveal a possible oligotrophic niche adaptation strategy of strain HTCC1062, which may help it gain a competitive advantage over other bacteria. Structure comparison and mutational analysis indicated that the TMAO binding mechanism of TmoX1062 may have differences from the previously reported mechanism of TmoX of Ruegeria pomeroyi DSS-3. This study provides new insight into TMAO utilization by the widespread SAR11 bacteria.

Genomic analysis of Marinomonas profundi M1K-6T reveals its adaptation to deep-sea environment of the Mariana Trench.

The Mariana Trench is the deepest site on earth with diverse extreme conditions such as high hydrostatic pressure, low temperature and lack of light. Organisms surviving in this extreme environment and their life strategies have been largely uninvestigated. Here, we report the complete genome of Marinomonas profundi M1K-6T, isolated from the Mariana Trench deep seawater. The assembled genome comprised 3,648,059 bp without any plasmid. Gene annotation showed that strain M1K-6T possesses a series of genes encoding cold-shock proteins, DEAD box RNA helicase and enzymes for biosynthesis of unsaturated fatty acids, implying its high cold tolerance. Abundant genes responsible for transports of ion, branched-chain amino acids and organic compatible solutes were detected, which could maintain cellular osmotic balance disturbed by high hydrostatic pressure. In addition, detected genes (related to storage carbon, transport systems and two-component regulatory systems) could help strain M1K-6T to improve its ecological fitness in the deep-sea microaerobic and nutrient-limiting environments. Genomic information on M. profundi M1K-6T, provides insights into the adaptation strategies of Marinomonas spp. in the extreme deep-sea environment of the Mariana Trench.

Celeribacter litoreus sp. nov., isolated from intertidal sediment.

A Gram-negative, aerobic, non-flagellated and rod-shaped bacterium, strain ASW11-22T, was isolated from an intertidal sediment collected from a coastal area of Qingdao, PR China. The strain grew at 15-40 °C (optimum, 37 °C), at pH 6.0-9.0 (optimum, pH 7.0) and with 0.5-10 % (w/v) NaCl (optimum, 1.0 %). It hydrolysed gelatin and aesculin but did not reduce nitrate to nitrite. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain ASW11-22T belonged to the genus Celeribacter, showing the highest sequence similarity to the type strains of Celeribacter halophilus MCCC 1A06432T (98.20 %) and Celeribacter ethanolicus NH195T (97.84 %). The genomic DNA G+C content was 59.1 mol%. The major cellular fatty acid (>10 %) of the strain was summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and its main polar lipids were phosphatidylglycerol and one unidentified aminolipid. The sole respiratory quinone of strain ASW11-22T was ubiquinone-10. On the basis of the polyphasic evidence presented in this paper, strain ASW11-22T represents a novel Celeribacter species, for which the name Celeribacter litoreus sp. nov. is proposed. The type strain is ASW11-22T (=KCTC 82495T=MCCC 1K05584T).

A Novel Gelatinase from Marine Flocculibacter collagenilyticus SM1988: Characterization and Potential Application in Collagen Oligopeptide-Rich Hydrolysate Preparation.

Although the S8 family in the MEROPS database contains many peptidases, only a few S8 peptidases have been applied in the preparation of bioactive oligopeptides. Bovine bone collagen is a good source for preparing collagen oligopeptides, but has been so far rarely applied in collagen peptide preparation. Here, we characterized a novel S8 gelatinase, Aa2_1884, from marine bacterium Flocculibacter collagenilyticus SM1988T, and evaluated its potential application in the preparation of collagen oligopeptides from bovine bone collagen. Aa2_1884 is a multimodular S8 peptidase with a distinct domain architecture from other reported peptidases. The recombinant Aa2_1884 over-expressed in Escherichia coli showed high activity toward gelatin and denatured collagens, but no activity toward natural collagens, indicating that Aa2_1884 is a gelatinase. To evaluate the potential of Aa2_1884 in the preparation of collagen oligopeptides from bovine bone collagen, three enzymatic hydrolysis parameters, hydrolysis temperature, hydrolysis time and enzyme-substrate ratio (E/S), were optimized by single factor experiments, and the optimal hydrolysis conditions were determined to be reaction at 60 ℃ for 3 h with an E/S of 400 U/g. Under these conditions, the hydrolysis efficiency of bovine bone collagen by Aa2_1884 reached 95.3%. The resultant hydrolysate contained 97.8% peptides, in which peptides with a molecular weight lower than 1000 Da and 500 Da accounted for 55.1% and 39.5%, respectively, indicating that the hydrolysate was rich in oligopeptides. These results indicate that Aa2_1884 likely has a promising potential application in the preparation of collagen oligopeptide-rich hydrolysate from bovine bone collagen, which may provide a feasible way for the high-value utilization of bovine bone collagen.

Genome sequencing and comparative genomics analysis of Halomonas sp. MT13 reveal genetic adaptation to deep-sea environment.

Halomonas sp. MT13, a moderately psychrotolerant, piezotolerant and exopolysaccharide-producing bacterium, was isolated from deep-sea sediment of the Mariana Trench at the depth of 8300 m. Here, we report the complete genome sequence of strain MT13 and its genomic characteristics related to deep-sea environmental adaptation by comparing with its three closely related Halomonas species. The genome of strain MT13 contains one circular chromosome of 3,643,760 bp without any plasmid. Gene annotation, Cluster of Orthologous Groups (COG) and KEGG analysis showed that strain MT13 possesses a serial of genes involved in deep-sea environmental adaptation, including ectoine biosynthesis, osmolyte transport, and cold-shock response. Compared with type strains of three closely related Halomonas species, strain MT13 has higher proportions of genes assigned to translation, ribosomal structure and biogenesis, and coenzyme, lipid and inorganic ion transport and metabolism, but lacks genes involved in flagellar assembly. The genome of strain MT13 would deepen our knowledge on the adaptation strategies of microorganisms dwelling in deep-sea environment.

Halomonas profundi sp. nov., isolated from deep-sea sediment of the Mariana Trench.

Two novel Gram-stain-negative, facultative anaerobic, non-flagellated, rod-shaped bacterial strains, designated MT13T and MT32, were isolated from sediment samples collected from the Mariana Trench at a depth of 8300 m. The two strains grew at -2-30 °C (optimum, 25 °C), at pH 5.5-10.0 (optimum, pH 7.5-8.0) and with 0-15 % (w/v) NaCl (optimum, 3-6 %). They did not reduce nitrate to nitrite nor hydrolyse Tweens 40 and 80, aesculin, casein, starch and DNA. The genomic G+C contents of draft genomes of strain MT13T and MT32 were 52.2 and 54.1 m ol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains MT13T and MT32 were affiliated with the genus Halomonas, with the highest similarity to the type strain of Halomonas olivaria. The values of average nucleotide identity and in silico DNA-DNA hybridization between strain MT13T and MT32, and between strain MT13T and five closely related type strains of Halomonas species indicated that strains MT13T and MT32 belonged to the same species, but represented a novel species in the genus of Halomonas. The major cellular fatty acids of strains MT13T and MT32 were C16 : 0, summed feature 3(C16 : 1 ω7c/ω6c) and summed feature 8 (C18 : 1 ω7c/ω6c). Major polar lipids of strains MT13T and MT32 included phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. Ubiquinone-9 was the predominant respiratory quinone. Based on data from the present polyphasic study, strains MT13T and MT32 represent a novel species of the genus Halomonas, for which the name Halomonas profundi sp. nov. is proposed. The type strain is MT13T (=MCCC 1K06389T=KCTC 82923T).

Description of Aureibaculum luteum sp. nov. and Aureibaculum flavum sp. nov. isolated from Antarctic intertidal sediments.

Two Gram-stain-negative, aerobic, non-motile, and rod-shaped bacterial strains, designated SM1352T and A20T, were isolated from intertidal sediments collected from King George Island, Antarctic. They shared 99.8% 16S rRNA gene sequence similarity with each other and had the highest sequence similarity of 98.1% to type strain of Aureibaculum marinum but < 93.4% sequence similarity to those of other known bacterial species. The genomes of strains SM1352T and A20T consisted of 5,108,092 bp and 4,772,071 bp, respectively, with the G + C contents both being 32.0%. They respectively encoded 4360 (including 37 tRNAs and 6 rRNAs) and 4032 (including 36 tRNAs and 5 rRNAs) genes. In the phylogenetic trees based on 16S rRNA gene and single-copy orthologous clusters (OCs), both strains clustered with Aureibaculum marinum and together formed a separate branch within the family Flavobacteriaceae. The ANI and DDH values between the two strains and Aureibaculum marinum BH-SD17T were all below the thresholds for species delineation. The major cellular fatty acids (> 10%) of the two strains included iso-C15:0, iso-C15:1 G, iso-C17:0 3-OH. Their polar lipids predominantly included phosphatidylethanolamine, one unidentified aminophospholipid, one unidentified aminolipid, and two unidentified lipids. Genomic comparison revealed that both strains possessed much more glycoside hydrolases and sulfatase-rich polysaccharide utilization loci (PULs) than Aureibaculum marinum BH-SD17T. Based on the above polyphasic evidences, strains SM1352T and A20T represent two novel species within the genus Aureibaculum, for which the names Aureibaculum luteum sp. nov. and Aureibaculum flavum sp. nov. are proposed. The type strains are SM1352T (= CCTCC AB 2014243 T = JCM 30335 T) and A20T (= CCTCC AB 2020370 T = KCTC 82503 T), respectively.

[Evaluation and Sources of Heavy Metal Pollution in the Surface Soil of the Qaidam Basin].

To understand surface soil heavy metal pollution characteristics, and the spatial distribution and sources of pollution in the main sedimentary features of the Qaidam Basin, a total of 129 topsoil samples(0-10 cm) were collected within a 25 km radius. The concentrations of As, Ba, Cr, Mn, Nb, Ni, Pb, Ti, Zn, Zr, and ten kinds of heavy metals were determined, the degree of contamination and potential sources quantitatively analyzed based on enrichment factors(EFs), the ground accumulation index(Igeo), and the absolute principal component-multiple linear regression(APCS-MLR) receptor model. The results showed that the surface soils of the Qaidam Basin have experienced pollution from ten kinds of heavy metals since the 1960s, with varying degrees of enrichment. As and Pb represent probable point source pollutants, and the basin as a whole shows negligible to low levels of pollution. The APCS-MLR analysis showed that heavy metal pollution derives from two sources, natural factors and anthropogenic(transportation) sources. Specifically, As, Cr, Mn, Nb, Ni, Ti, Zn, and Zr are associated with natural sources, while Ba and Pb are associated with both natural and anthropogenic sources.