Pseudopontixanthobacter vadosimaris gen. nov., sp. nov., isolated from shallow sea near Kueishan Island.

A Gram-stain-negative and aerobic bacterial strain, designated as JL3514T, was isolated from surface water of the hydrothermal system around Kueishan Island. The isolate formed red colonies and cells were non-flagellated, rod-shaped and contained methanol-soluble pigments. Growth was observed at 10-50 °C (optimum, 30 °C), at pH 5.0-9.0 (optimum, pH 7.0) and in the presence of 0-9 % (w/v) NaCl (optimum, 2 %). Strain JL3514T was positive for catalase and weakly positive for oxidase. Results of 16S rRNA gene sequence analyses showed highest similarities to species in the family Erythrobacteraceae, namely Croceibacterium atlanticum (96.1 %), Pelagerythrobacter marensis (96.0 %), Tsuneonella rigui (96.0 %) and Altericroceibacterium xinjiangense (96.0 %). Phylogenetic analysis based on core gene sequences revealed that the isolate formed a distinct branch with the related species and it had a lower average amino acid identity value than the suggested threshold for genera boundaries. The major fatty acids (>5 %) were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0, C17 : 1 ω6c, C14 : 0 2-OH and C12 : 0. The dominant polar lipids comprised diphosphatidylglycerol, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, glycolipid, two unidentified lipids and one unidentified phospholipid. The main respiratory quinones were ubiquinone-10 (95.7 %) and ubiquinone-9 (4.3 %). The DNA G+C content from the genome was 63.0 mol%. Based on the presented data, we consider strain JL3514T to represent a novel genus of the family Erythrobacteraceae, with the name Pseudopontixanthobacter vadosimaris gen. nov., sp. nov. The type strain is JL3514T (=KCTC 62623T=MCCC 1K03561T).

Discovery of benzoheterocyclic-substituted amide derivatives as apoptosis signal-regulating kinase 1 (ASK1) inhibitors.

Three series of benzoheterocyclic-substituted amide derivatives were designed and synthesized as potent ASK1 inhibitors in this work. After undergoing continuous structural optimization, compound 17a was discovered to be a novel inhibitor of ASK1 with good potency (kinase, IC50 = 26 nM), noteworthy liver microsomal stability (human, T1/2 = 340.4 min), good pharmacokinetic parameters (rat, T1/2 p.o. = 2.11 h, AUClast p.o. = 10 900 h ng mL-1) and high oral bioavailability (rat, F = 97.9%), while also being inactive towards hERG (IC50 > 10 µM).

Diversity and potential host-interactions of viruses inhabiting deep-sea seamount sediments.

Seamounts are globally distributed across the oceans and form one of the major oceanic biomes. Here, we utilized combined analyses of bulk metagenome and virome to study viral communities in seamount sediments in the western Pacific Ocean. Phylogenetic analyses and the protein-sharing network demonstrate extensive diversity and previously unknown viral clades. Inference of virus-host linkages uncovers extensive interactions between viruses and dominant prokaryote lineages, and suggests that viruses play significant roles in carbon, sulfur, and nitrogen cycling by compensating or augmenting host metabolisms. Moreover, temperate viruses are predicted to be prevalent in seamount sediments, which tend to carry auxiliary metabolic genes for host survivability. Intriguingly, the geographical features of seamounts likely compromise the connectivity of viral communities and thus contribute to the high divergence of viral genetic spaces and populations across seamounts. Altogether, these findings provides knowledge essential for understanding the biogeography and ecological roles of viruses in globally widespread seamounts.

Diverse Subclade Differentiation Attributed to the Ubiquity of Prochlorococcus High-Light-Adapted Clade II.

Prochlorococcus is the key primary producer in marine ecosystems, and the high-light-adapted clade II (HLII) is the most abundant ecotype. However, the genomic and ecological basis of Prochlorococcus HLII in the marine environment has remained elusive. Here, we show that the ecologically coherent subclade differentiation of HLII corresponds to genomic and ecological characteristics on the basis of analyses of 31 different strains of HLII, including 12 novel isolates. Different subclades of HLII with different core and accessory genes were identified, and their distribution in the marine environment was explored using the TARA Oceans metagenome database. Three major subclade groups were identified, viz., the surface group (HLII-SG), the transition group (HLII-TG), and the deep group (HLII-DG). These subclade groups showed different temperature ranges and optima for distribution. In regression analyses, temperature and nutrient availability were identified as key factors affecting the distribution of HLII subclades. A 35% increase in the relative abundance of HLII-SG by the end of the 21st century was predicted under the Representative Concentration Pathway 8.5 scenario. Our results show that the ubiquity and distribution of Prochlorococcus HLII in the marine environment are associated with the differentiation of diverse subclades. These findings provide insights into the large-scale shifts in the Prochlorococcus community in response to future climate change. IMPORTANCEProchlorococcus is the most abundant oxygenic photosynthetic microorganism on Earth, and high-light-adapted clade II (HLII) is the dominant ecotype. However, the factors behind the dominance of HLII in the vast oligotrophic oceans are still unknown. Here, we identified three distinct groups of HLII subclades, viz., the surface group (HLII-SG), the transition group (HLII-TG), and the deep group (HLII-DG). We further demonstrated that the ecologically coherent subclade differentiation of HLII corresponds to genomic and ecological characteristics. Our study suggests that the differentiation of diverse subclades underlies the ubiquity and distribution of Prochlorococcus HLII in the marine environment and provides insights into the shifts in the Prochlorococcus community in response to future climate change.

A Novel Broad Host Range Phage Infecting Alteromonas.

Bacteriophages substantially contribute to bacterial mortality in the ocean and play critical roles in global biogeochemical processes. Alteromonas is a ubiquitous bacterial genus in global tropical and temperate waters, which can cross-protect marine cyanobacteria and thus has important ecological benefits. However, little is known about the biological and ecological features of Alteromonas phages (alterophages). Here, we describe a novel alterophage vB_AmeP-R8W (R8W), which belongs to the Autographiviridae family and infects the deep-clade Alteromonas mediterranea. R8W has an equidistant and icosahedral head (65 ± 1 nm in diameter) and a short tail (12 ± 2 nm in length). The genome size of R8W is 48,825 bp, with a G + C content of 40.55%. R8W possesses three putative auxiliary metabolic genes encoding proteins involved in nucleotide metabolism and DNA binding: thymidylate synthase, nucleoside triphosphate pyrophosphohydrolase, and PhoB. R8W has a rapid lytic cycle with a burst size of 88 plaque-forming units/cell. Notably, R8W has a wide host range, such that it can infect 35 Alteromonas strains; it exhibits a strong specificity for strains isolated from deep waters. R8W has two specific receptor binding proteins and a compatible holin-endolysin system, which contribute to its wide host range. The isolation of R8W will contribute to the understanding of alterophage evolution, as well as the phage-host interactions and ecological importance of alterophages.