Tepidibacillus marianensis sp. nov., a novel heterotrophic iron-reducing bacterium isolated from Mariana Trench sediment.

A novel chemoheterotrophic iron-reducing micro-organism, designated as strain LSZ-M11000T, was isolated from sediment of the Marianas Trench. Phylogenetic analysis based on the 16S rRNA gene revealed that strain LSZ-M11000T belonged to genus Tepidibacillus, with 97 % identity to that of Tepidibacillus fermentans STGHT, a mesophilic bacterium isolated from the Severo-Stavropolskoye underground gas storage facility in Russia. The polar lipid profile of strain LSZ-M11000T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, as well as other unidentified phospholipids and lipids. The major fatty acids were C16 : 0 (28.4 %), C18 : 0 (15.8 %), iso-C15 : 0 (12.9 %), and anteiso-C15 : 0 (12.0 %). Strain LSZ-M11000T had no menaquinone. Genome sequencing revealed that the genome size of strain LSZ-M11000T was 2.97 Mb and the DNA G+C content was 37.9 mol%. The average nucleotide identity values between strain LSZ-M11000T and its close phylogenetic relatives, Tepidibacillus fermentans STGHT and Tepidibacillus decaturensis Z9T, were 76.4 and 72.6 %, respectively. The corresponding DNA-DNA hybridization estimates were 20.9 and 23.4 %, respectively. Cells of strain LSZ-M11000T were rod-shaped (1.0-1.5×0.3-0.5 µm). Using pyruvate as an electron donor, it was capable of reducing KMnO4, MnO2, As(V), NaNO3, NaNO2, Na2SO4, Na2S2O3, and K2Cr2O7. Based on phenotypic, genotypic, and phylogenetic evidence, strain LSZ-M11000T is proposed to be a novel strain of the genus Tepidibacillus, for which the name Tepdibacillus marianensis is proposed. The type strain is LSZ-M11000T (=CCAM 1008T=JCM 39431T).

A Hadal Streptomyces-Derived Echinocandin Acylase Discovered through the Prioritization of Protein Families.

Naturally occurring echinocandin B and FR901379 are potent antifungal lipopeptides featuring a cyclic hexapeptide nucleus and a fatty acid side chain. They are the parent compounds of echinocandin drugs for the treatment of severe fungal infections caused by the Candida and Aspergilla species. To minimize hemolytic toxicity, the native fatty acid side chains in these drug molecules are replaced with designer acyl side chains. The deacylation of the N-acyl side chain is, therefore, a crucial step for the development and manufacturing of echinocandin-type antibiotics. Echinocandin E (ECE) is a novel echinocandin congener with enhanced stability generated via the engineering of the biosynthetic machinery of echinocandin B (ECB). In the present study, we report the discovery of the first echinocandin E acylase (ECEA) using the enzyme similarity tool (EST) for enzymatic function mining across protein families. ECEA is derived from Streptomyces sp. SY1965 isolated from a sediment collected from the Mariana Trench. It was cloned and heterologously expressed in S. lividans TK24. The resultant TKecea66 strain showed efficient cleavage activity of the acyl side chain of ECE, showing promising applications in the development of novel echinocandin-type therapeutics. Our results also provide a showcase for harnessing the essentially untapped biodiversity from the hadal ecosystems for the discovery of functional molecules.

New Sulfurated Butyrolactones from the Fungus Penicillium janthinellum.

Deep-sea derived fungi are considered as significant resources to discovery structurally diverse and biologically active natural compounds. In this study, four new sulfurated butyrolactones, penijanthiones A-D (1-4), together with four known analogues (5-8), were isolated from a Mariana Trench-derived fungus Penicilliumjanthinellum SH0301. Compounds 1-4 were the undescribed examples for natural butyrolactones coupling with a mercaptolactate moiety. Their structures including the absolute configurations of these new compounds were elucidated by comprehensive spectroscopic data, and calculated electronic circular dichroism (ECD). The plausible biosynthetic pathway of sulfur-incorporation of 1-4 was proposed. All of these isolated compounds were evaluated their cytotoxic, antimicrobial and antiviral activities.

Microbial Dimethylsulfoniopropionate Cycling in Deep Sediment of the Mariana Trench.

Dimethylsulfoniopropionate (DMSP) and related organic sulfur compounds play key roles in global sulfur cycling. Bacteria have been found to be important DMSP producers in seawater and surface sediments of the aphotic Mariana Trench (MT). However, detailed bacterial DMSP cycling in the Mariana Trench subseafloor remains largely unknown. Here, the bacterial DMSP-cycling potential in a Mariana Trench sediment core (7.5 m in length) obtained at a 10,816-m water depth was investigated using culture-dependent and -independent methods. The DMSP content fluctuated along the sediment depth and reached the highest concentration at 15 to 18 cm below the seafloor (cmbsf). dsyB was the dominant known DMSP synthetic gene, existing in 0.36 to 1.19% of the bacteria, and was identified in the metagenome-assembled genomes (MAGs) of previously unknown bacterial DMSP synthetic groups such as Acidimicrobiia, Phycisphaerae, and Hydrogenedentia. dddP, dmdA, and dddX were the major DMSP catabolic genes. The DMSP catabolic activities of DddP and DddX retrieved from Anaerolineales MAGs were confirmed by heterologous expression, indicating that such anaerobic bacteria might participate in DMSP catabolism. Moreover, genes involved in methanethiol (MeSH) production from methylmercaptopropionate (MMPA) and dimethyl sulfide (DMS), MeSH oxidation, and DMS production were highly abundant, suggesting active conversions between different organic sulfur compounds. Finally, most culturable DMSP synthetic and catabolic isolates possessed no known DMSP synthetic and catabolic genes, and actinomycetes could be important groups involved in both DMSP synthesis and catabolism in Mariana Trench sediment. This study extends the current understanding of DMSP cycling in Mariana Trench sediment and highlights the need to uncover novel DMSP metabolic genes/pathways in extreme environments. IMPORTANCE Dimethylsulfoniopropionate (DMSP) is an abundant organosulfur molecule in the ocean and is the precursor for the climate-active volatile gas dimethyl sulfide. Previous studies focused mainly on bacterial DMSP cycling in seawater, coastal sediment, and surface trench sediment samples, but DMSP metabolism in the Mariana Trench (MT) subseafloor sediments remains unknown. Here, we describe the DMSP content and metabolic bacterial groups in the subseafloor of the MT sediment. We found that the tendency for vertical variation of the DMSP content in the MT was distinct from that of the continent shelf sediment. Although dsyB and dddP were the dominant DMSP synthetic and catabolic genes in the MT sediment, respectively, both metagenomic and culture methods revealed multiple previously unknown DMSP metabolic bacterial groups, especially anaerobic bacteria and actinomycetes. The active conversion of DMSP, DMS, and methanethiol may also occur in the MT sediments. These results provide novel insights for understanding DMSP cycling in the MT.

Profundirhabdus halotolerans gen. nov., sp. nov., an haloalkaliphilic actinobacterium isolated from seawater of the Mariana Trench.

A Gram-stain-positive, strictly aerobic, rod-shaped actinobacterium, designated strain ZYF776T, was isolated from seawater of the Mariana Trench collected at a depth of 4000 m. Results of 16S rRNA gene sequence analysis indicated that strain ZYF776T was a member of the class Nitriliruptoria and closely related to Nitriliruptor alkaliphilus DSM 45188T (member of the order Nitriliruptorales, 94.94 % sequence similarity) and Egicoccus halophilus KCTC 33612T (member of the order Egicoccales, 94.46 %). Strain ZYF776T was catalase-positive and oxidase-negative. Growth occurred at 16-37 °C (optimum, 28 °C), in the presence of 0-13 % NaCl (w/v; optimum, 4 %) and at pH 7.0-10.0 (optimum, pH 8.0). Cell-wall hydrolysates of strain ZYF776T contained meso-diaminopimelic (peptidoglycan type A1γ), with ribose, rhamnose and a smaller amount of xylose as the cell-wall sugars. The major menaquinone was MK-10. The predominant fatty acids (>10 %) were C16:0, C17:1 ω8c and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The polar lipid profile mainly contained diphosphatidylglycerol, phosphatidylglycerol and phosphoglycolipid. The genomic DNA G+C content of strain ZYF776T was 68.7 mol%. The genome of strain ZYF776T was about 5.61 Mbp in size, which was larger than those of the reference strains N. alkaliphilus DSM45188T (5.56 Mbp) and E. halophilus KCTC 33612T (3.98 Mbp). The average nucleotide identity and digital DNA-DNA hybridization values between ZYF776T and the related strains N. alkaliphilus DSM 45188T and E. halophilus KCTC 33612T were 76.7 and 20.3 % and 75.8 and 20.0 %, respectively. Based on the polyphasic evidence, a novel genus and species with the name Profundirhabdus halotolerans gen. nov., sp. nov. is proposed. The type strain is ZYF776T (=JCM 33008T=MCCC 1K03555T).

Aurantimonas marianensis sp. nov., isolated from deep-sea sediment of the Mariana Trench.

A novel strain, designated as LRZ36T, was isolated from deep-sea sediment (from a depth of 5400 m) from the Mariana Trench. Cells of this strain are rod-shaped, Gram-stain-negative, strictly aerobic and non-motile. Phylogenetic analysis of LRZ36T based on 16S rRNA gene sequences revealed a lineage in the family Aurantimonadaceae but distinct from the most closely related species Aurantimonas marina CGMCC 1.17725T, 'Aurantimonas litoralis' KCTC 12094 and Aurantimonas coralicida DSM 14790T with sequence identities of 99.4 %, 98.0 and 97.9 %, respectively. The genome of LRZ36T was 3.8 Mbp in size with a DNA G+C content of 64.8 %, containing 3623 predicted coding genes. LRZ36T showed average nucleotide identity values of 89.8 %, 78.7 and 78.5 % and digital DNA-DNA hybridization values of 38.9 %, 21.7 and 21.6 % with A. marina CGMCC 1.17725T, 'A. litoralis' KCTC 12094 and A. coralicida DSM 14790T, respectively. The major respiratory quinone was ubiquinone-10 (Q-10), and the predominant fatty acids were C18 : 1ω7c (74.4 %) and C16 : 0 (12.1 %). The polar lipids in LRZ36T are diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylcholine, phosphatidylinositol mannoside, an unidentified aminophospholipid, three unidentified lipids, three unidentified phospholipids and two unidentified aminolipids. On the basis of genotypic and phenotypic evidence, LRZ36T represents a novel species of the genus Aurantimonas, for which the name Aurantimonas marianensis sp. nov. is proposed. The type strain is LRZ36T (= KCTC 92065T = GDMCC 1.2985T=MCCC 1K07227T).

Abyssibius alkaniclasticus gen. nov., sp. nov., a novel member of the family Rhodobacteraceae, isolated from the Mariana Trench.

A Gram-stain-negative bacterium with rod-shaped or irregular cells approximately 0.5-0.9×2.0-3.8 µm in size, designated as 960558T, was isolated from sediment sampled in the Mariana Trench. Strain 960558T grows at 4-37 °C (optimum, 28 °C), pH 6-7 (optimum, pH 7) and in the presence of 1-5 % (w/v) NaCl (optimum, 3 %). Strain 960558T utilizes tetradecane or hexadecane as a sole carbon and energy source, respectively. Phylogenetic trees based on 16S rRNA gene sequences and phylogenomic reconstruction revealed a close phylogenetic relationship between strain 960558T and members of the family Rhodobacteraceae by forming a separate branch within the type species of closely related genera. The validly published species that is most closely related to strain 960558T is Planktotalea lamellibrachiae JAM 119T, which has the highest 16S rRNA gene sequence similarity (93.47 %). Ubiquinone 10 is the predominant ubiquinone, while C16 : 0, 11-methyl C18 : 1 ω7c and C18 : 1 ω7c and/or C18 : 1 ω6c are the predominant fatty acids (>10 %). Additionally, phosphatidylglycerol, glycolipids, diphosphatidylglycerol, unidentified polar lipids and unidentified aminolipids are the major polar lipids. The DNA G+C content of strain 960558T is 61 %. Average nucleotide identity and digital DNA-DNA hybridization results of strain 960558T with other type strains are <70.2 and 22.1 %, respectively. Based on its phylogenetic, chemotaxonomic and other phenotypic properties, strain 960558T is considered to represent a novel genus and species within the family Rhodobacteraceae, for which the name Abyssibius alkaniclasticus gen. nov., sp. nov. is proposed. The type strain of Abyssibius alkaniclasticus is 960558T (=KCTC 82619T=MCCC 1K04727T).

Effects of Epigenetic Modification and High Hydrostatic Pressure on Polyketide Synthase Genes and Secondary Metabolites of Alternaria alternata Derived from the Mariana Trench Sediments.

The hadal biosphere is the most mysterious ecosystem on the planet, located in a unique and extreme environment on Earth. To adapt to extreme environmental conditions, hadal microorganisms evolve special strategies and metabolisms to survive and reproduce. However, the secondary metabolites of the hadal microorganisms are poorly understood. In this study, we focused on the isolation and characterization of hadal fungi, screening the potential strains with bioactive natural products. The isolates obtained were detected further for the polyketide synthase (PKS) genes. Two isolates of Alternaria alternata were picked up as the representatives, which had the potential to synthesize active natural products. The epigenetic modifiers were used for the two A. alternata isolates to stimulate functional gene expression in hadal fungi under laboratory conditions. The results showed that the chemical epigenetic modifier, 5-Azacytidine (5-Aza), affected the phenotype, PKS gene expression, production of secondary metabolites, and antimicrobial activity of the hadal fungus A. alternata. The influence of epigenetic modification on natural products was strongest when the concentration of 5-Aza was 50 µM. Furthermore, the modification of epigenetic agents on hadal fungi under high hydrostatic pressure (HHP) of 40 MPa displayed significant effects on PKS gene expression, and also activated the production of new compounds. Our study demonstrates the high biosynthetic potential of cultivable hadal fungi, but also provides evidence for the utility of chemical epigenetic modifiers on active natural products from hadal fungi, providing new ideas for the development and exploitation of microbial resources in extreme environments.

Pseudomonas marianensis sp. nov., a marine bacterium isolated from deep-sea sediments of the Mariana Trench.

A novel marine Gram-stain-negative, aerobic, rod-shaped bacterium, designated as strain PS1T, was isolated from the deep-sea sediments of the Mariana Trench and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 35 °C (ranging 10-45 °C), pH 6 (ranging pH 5-10) and with 11% (w/v) NaCl (ranging 0-17%). The 16S rRNA gene sequence similarity results revealed that strain PS1T was most closely related to Pseudomonas stutzeri ATCC 17588T, Pseudomonas nitrititolerans GL14T, Pseudomonas zhaodongensis NEAU-ST5-21T, Pseudomonas xanthomarina DSM 18231T and Pseudomonas kunmingensis HL22-2T with 98.3-98.7%. The digital DNA-DNA hybridization values and the average nucleotide identity between strain PS1T and the reference strains were 20.4-40.1% and 78.7-79.4%, respectively. The major respiratory quinone is ubiquinone Q-9. The major polar lipids were phosphatidylethanolamine, diphosphatidyglycerol, phosphatidylglycerol, phosphatidylcholine, aminoglycolipid, two unidentified glycolipids and one unidentified lipid. The predominant cellular fatty acids of strain PS1T were summed feature 8 (C18:1ω7c and/or C18:1ω6c), summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0 and cyclo-C19:0 ω8c. The G + C content of the genomic DNA was 63.0%. The combined genotypic and phenotypic data indicated that strain PS1T represents a novel species of the genus Pseudomonas, for which the name Pseudomonas marianensis sp. nov. is proposed, with the type strain PS1T (= DSM 112238T = MCCC 1K05112T).

Description of Abyssalbus ytuae gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from the sediment of the Mariana Trench.

In this study, we describe a Gram-stain-negative, rod-shaped, non-motile and aerobic bacterium, named strain MT3330T, which was isolated from the deep-sea sediment of the Mariana Trench. Growth of MT3330T occurred at 15-40 °C (optimum, 25-30 °C), pH 5.0-10.0 (optimum, 7.0-8.0) and with 0-8.0 % (w/v) NaCl (optimum, 0-2.0 %). The results of phylogenetic analysis based on 16S rRNA gene sequence indicated that MT3330T represented a member of the family Flavobacteriaceae and was most closely related to Zhouia spongiae HN-Y44T (92.3 % sequence similarity). The results of genomic analysis indicated that MT3330T contains a circular chromosome of 4 365 036 bp with a DNA G+C content of 35.2 %. The predominant respiratory quinone of MT3330T was MK-6. The polar lipids of MT3330T included phosphatidylethanolamine, three unidentified amino lipids and four unidentified lipids. The major fatty acids of MT3330T included C15 : 0, iso-C15 : 1G, iso-C15 : 0 3-OH, and iso-C17 : 0 3-OH. On the basis of the results of the phylogenetic, physiological, biochemical and morphological analyses, it is suggested that strain MT3330T represents a novel genus and a novel species of the family Flavobacteriaceae, and the name Abyssalbus ytuae gen. nov., sp. nov. is proposed. The type strain is MT3330T (=MCCC 1K06012T=KCTC 82823T).

Methylophaga pinxianii sp. nov., isolated from the Mariana Trench.

Two strains, TMB456T and TMB1265, were isolated from different locations in the Mariana Trench. Analysis of the 16S rRNA gene and genomic rRNA sequences indicated that they were from the same novel species and were affiliated with the genus Methylophaga of the class Gammaproteobacteria. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the most closely related validly published species were Methylophaga muralis Kr3T (98.1 % similarity) and Methylophaga nitratireducenticrescens JAM1T (97.3 % similarity). Digital DNA-DNA hybridization values of TMB456T with M. muralis Kr3T and M. nitratireducenticrescens JAM1T were <25 %. The average nucleotide identity value between strain TMB456T and M. muralis Kr3T was 80.9 %. The genomic DNA G+C contents of strains TMB456T and TMB1265 were both 44.9 mol %. Strains TMB456T and TMB1265 could grow at 4-37 °C (optimum at 20-28 °C), at pH 3-10 (optimum at pH 7-9) and in the presence of 0-10 % (w/v) NaCl (optimum at 0-1 %). Cells of strains TMB456T and TMB1265 were Gram-negative rods (0.3-0.6 µm×0.7-1.3 µm). Chemotaxonomic analysis showed that ubiquinone 8 was the sole quinone produced by strain TMB456T and that the major cellular fatty acids were iso-C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The polar lipid profile of this strain included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphoglycolipids and two unidentified polar lipids. Based on the phenotypic, chemotaxonomic and molecular features, strains TMB456T and TMB1265 belong to a novel species within the genus Methylophaga, for which the name Methylophaga pinxianii sp. nov. is proposed. The type strain is TMB456T (=KCTC 82622T= MCCC 1K05898T).

Thalassolituus alkanivorans sp. nov., a hydrocarbon-utilizing bacterium isolated from the Mariana Trench.

Two strains, TMPB967T and TTPB476, were isolated from two different locations in the Mariana Trench. Cells of strains TMPB967T and TTPB476 were Gram-negative, curved rod-shaped (0.35-0.6 µm×2-4 µm) with flagella. Both strains were catalase- and oxidase-positive. Strains TMPB967T and TTPB476 could grow at 4-37 °C (optimum, 37 °C), at pH 6-9 (optimum, pH 6-7) and in the presence of 0-8 % (w/v) NaCl (optimum, 5 %). Both strains could grow with tetradecane or hexadecane as the sole carbon source. The predominant isoprenoid quinone was ubiquinone 9. The major cellular fatty acids of strains TMPB967T and TTPB476 were C18 : 1 ω9c, C16 : 0 and summed feature 3 (C16 : 1 ω7c or ω6c). The polar lipid profile included phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unknown aminolipid. The DNA G+C contents of strains TMPB967T and TTPB476 were 53.1 and 53.0 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the most closely related validly published species were Thalassolituus marinus IMCC1826T (97.1 % similarity) and Thalassolituus oleivorans MIL-1T (95.9 % similarity). Digital DNA-DNA hybridization results of strain TMPB967T with TTPB476, T. marinus IMCC1826T and T. oleivorans MIL-1T were 99.9, 20.9 and 20.2 %, respectively. Average nucleotide identity results of strain TMPB967T with TTPB476, T. marinus IMCC1826T and T. oleivorans MIL-1T were 100, 75.8 and 72.0 %, respectively. On the basis of the phenotypic, chemotaxonomic and molecular features, strains TMPB967T and TTPB476 belong to a novel species within the genus Thalassolituus, for which the name Thalassolituus alkanivorans sp. nov. is proposed. The type strain is TMPB967T (=KCTC 82621T=MCCC 1K05476T).

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).

Comparison of Deep-Sea Picoeukaryotic Composition Estimated from the V4 and V9 Regions of 18S rRNA Gene with a Focus on the Hadal Zone of the Mariana Trench.

Diversity of microbial eukaryotes is estimated largely based on sequencing analysis of the hypervariable regions of 18S rRNA genes. But the use of different regions of 18S rRNA genes as molecular markers may generate bias in diversity estimation. Here, we compared the differences between the two most widely used markers, V4 and V9 regions of the 18S rRNA gene, in describing the diversity of epipelagic, bathypelagic, and hadal picoeukaryotes in the Challenger Deep of the Mariana Trench, which is a unique and little explored environment. Generally, the V9 region identified more OTUs in deeper waters than V4, while the V4 region provided greater Shannon diversity than V9. In the epipelagic zone, where Alveolata was the dominant group, picoeukaryotic community compositions identified by V4 and V9 markers are similar at different taxonomic levels. However, in the deep waters, the results of the two datasets show clear differences. These differences were mainly contributed by Retaria, Fungi, and Bicosoecida. The primer targeting the V9 region has an advantage in amplifying Bicosoecids in the bathypelagic and hadal zone of the Mariana Trench, and its high abundance in V9 dataset pointed out the possibility of Bicosoecids as a dominant group in this environment. Chrysophyceae, Fungi, MALV-I, and Retaria were identified as the dominant picoeukaryotes in the bathypelagic and hadal zone and potentially play important roles in deep-sea microbial food webs and biogeochemical cycling by their phagotrophic, saprotrophic, and parasitic life styles. Overall, the use of different markers of 18S rRNA gene allows a better assessment and understanding of the picoeukaryotic diversity in deep-sea environments.

Pontivivens ytuae sp. nov., isolated from deep sea sediment of the Mariana Trench.

A Gram-stain-negative, light pink-coloured, rod-shaped, flagellated and facultative anaerobic bacterial strain, designated MT2928T, was isolated from deep-sea sediment collected from the Mariana Trench. Growth of strain MT2928T occurred optimally at 28 °C, pH 8.0-9.0 and in the presence of 1.0-2.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain MT2928T belongs to the genus Pontivivens and has the highest sequence similarity to Pontivivens insulae GYSW-23T (96.6 %). Genomic analysis indicated that strain MT2928T contains a circular chromosome of 4 199 362 bp with G+C content of 67.2 mol%. The strain did not produce bacteriochlorophyll a, but produced carotenoid. The predominant respiratory quinone of MT2928T was ubiquinone-10. The polar lipids of MT2928T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two unidentified lipids and two unidentified phospholipids. The major fatty acids of strain MT2928T contained summed feature 8 (C18 : 1 ω7c or/and C18 : 1 ω6c), C18 : 0 and summed feature 2 (iso-C16 : 1 I and/or C14 : 0 3-OH). On the basis of phylogenetic, physiological, biochemical and other phenotypic properties, strain MT2928T represents a novel species of the genus Pontivivens, and the name Pontivivens ytuae sp. nov. is proposed with the type species MT2928T (=MCCC 1K05575T=JCM 34320T).

Description of Novosphingopyxis iocasae sp. nov., isolated from deep sea sediment from the Mariana Trench, and emended description of the genus Novosphingopyxis.

In this study, we reported a Gram-stain-negative, orange-coloured, rod-shaped, motile and faculatively anaerobic bacterium named strain PB63T, which was isolated from the deep-sea sediment from the Mariana Trench. Growth of PB63T occurred at 10-35 °C (optimum, 28 °C), pH 5.0-8.0 (optimum, 5.0-6.0) and with 0-7 % (w/v) NaCl (optimum, 2-3 %). The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that PB63T represented a member of the genus Novosphingopyxis and was closely related to Novosphingopyxis baekryungensis DSM 16222T (97.9 % sequence similarity). PB63T showed tolerance to a variety of heavy metals, including Co2+, Zn2+, Mn2+ and Cu2+. The complete genome of PB63T was obtained, and many genes involved in heavy metal resistance were found. The genomic DNA G+C content of PB63T was 62.8 mol%. The predominant respiratory quinone of PB63T was ubiquinone-10 (Q-10). The polar lipids of PB63T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, glycolipid, phosphatidylcholines and three unidentified lipids. The major fatty acids of PB63T included summed feature 8 (C18 : 1ω7c or/and C18 : 1ω6c), C14 : 0 2-OH, 11-methyl C18 : 1ω7c, C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C17 : 1ω6c. The results of phylogenetic, physiological, biochemical and morphological analyses indicated that strain PB63T represents a novel species of the genus Novosphingopyxis, and the name Novosphingopyxis iocasae sp. nov. is proposed with the type species PB63T (=CCTCC AB 2019195T=JCM 34178T).

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).

Biotechnological and Ecological Potential of Micromonospora provocatoris sp. nov., a Gifted Strain Isolated from the Challenger Deep of the Mariana Trench.

A Micromonospora strain, isolate MT25T, was recovered from a sediment collected from the Challenger Deep of the Mariana Trench using a selective isolation procedure. The isolate produced two major metabolites, n-acetylglutaminyl glutamine amide and desferrioxamine B, the chemical structures of which were determined using 1D and 2D-NMR, including 1H-15N HSQC and 1H-15N HMBC 2D-NMR, as well as high resolution MS. A whole genome sequence of the strain showed the presence of ten natural product-biosynthetic gene clusters, including one responsible for the biosynthesis of desferrioxamine B. Whilst 16S rRNA gene sequence analyses showed that the isolate was most closely related to the type strain of Micromonospora chalcea, a whole genome sequence analysis revealed it to be most closely related to Micromonospora tulbaghiae 45142T. The two strains were distinguished using a combination of genomic and phenotypic features. Based on these data, it is proposed that strain MT25T (NCIMB 15245T, TISTR 2834T) be classified as Micromonospora provocatoris sp. nov. Analysis of the genome sequence of strain MT25T (genome size 6.1 Mbp) revealed genes predicted to responsible for its adaptation to extreme environmental conditions that prevail in deep-sea sediments.

Dermacozine N, the First Natural Linear Pentacyclic Oxazinophenazine with UV-Vis Absorption Maxima in the Near Infrared Region, along with Dermacozines O and P Isolated from the Mariana Trench Sediment Strain Dermacoccus abyssi MT 1.1T.

Three dermacozines, dermacozines N-P (1-3), were isolated from the piezotolerant Actinomycete strain Dermacoccus abyssi MT 1.1T, which was isolated from a Mariana Trench sediment in 2006. Herein, we report the elucidation of their structures using a combination of 1D/2D NMR, LC-HRESI-MSn, UV-Visible, and IR spectroscopy. Further confirmation of the structures was achieved through the analysis of data from density functional theory (DFT)-UV-Visible spectral calculations and statistical analysis such as two tailed t-test, linear regression-, and multiple linear regression analysis applied to either solely experimental or to experimental and calculated 13C-NMR chemical shift data. Dermacozine N (1) bears a novel linear pentacyclic phenoxazine framework that has never been reported as a natural product. Dermacozine O (2) is a constitutional isomer of the known dermacozine F while dermacozine P (3) is 8-benzoyl-6-carbamoylphenazine-1-carboxylic acid. Dermacozine N (1) is unique among phenoxazines due to its near infrared (NIR) absorption maxima, which would make this compound an excellent candidate for research in biosensing chemistry, photodynamic therapy (PDT), opto-electronic applications, and metabolic mapping at the cellular level. Furthermore, dermacozine N (1) possesses weak cytotoxic activity against melanoma (A2058) and hepatocellular carcinoma cells (HepG2) with IC50 values of 51 and 38 µM, respectively.

Muricauda hadalis sp. nov., a novel piezophile isolated from hadopelagic water of the Mariana Trench and reclassification of Muricauda antarctica as a later heterotypic synonym of Muricauda teanensis.

A novel marine Gram-stain-negative, non-motile, aerobic and rod-shaped bacterium, designated as strain MT-229T, was isolated from the deep seawater in the Mariana Trench and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 30 °C (ranging 10-40 °C), pH 6 (ranging 3-11) and with 11 % (w/v) NaCl (ranging 0-17 %). Strain MT-229T was a piezophile, growing optimally at 20 MPa (range 0.1-70 MPa). The nearest phylogenetic neighbours were Muricauda antarctica CGMCC 1.2174T and Muricauda taeanensis JCM 17757T with 16S rRNA gene similarity of 98.7 %. The sole respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine (PE), two unidentified aminolipids (AL) and ten unidentified lipids. The major fatty acids of strain MT-229T were iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G. The G+C content of the genomic DNA was 45.6 mol%. The combined genotypic and phenotypic data indicated that strain MT-229T represents a novel species of the genus Muricauda, for which the name Muricauda hadalis sp. nov. is proposed, with the type strain MT-229T (=DSM 109894T=MCCC 1K04201T). In addition, the whole-genome-based comparisons revealed that the type strains of Muricauda antarctica and Muricauda teanensis belong to a single species. It is, therefore, proposed that M. antarctica be recognized as a heterotypic synonym of M. teanensis.