The rapid decline of sea ice in the western Arctic Ocean over the past decade has raised concerns about its ecological impacts, particularly on copepod communities, which play a key role in pelagic-benthic coupling. However, the responses of copepods to sea ice retreat remain uncertain, as these responses may vary across different habitats and species. To evaluate the inter-annual variability of copepod communities and their potential responses to sea ice decline, we analyzed copepod samples collected during the summers of 2003, 2008, 2010, and 2012. Three geographically separate habitats and four ecological groups of copepods were identified, with inter-annual variability observed within habitats and ecological groups. In 2012, total copepod abundance significantly increased in the Chukchi Shelf (CS) and slope/plateau (CSP) habitats, while a decreasing trend was observed in the Canada Basin (CB). Among the four ecological groups, we identified horizontal advective flux-correlated inter-annual variability in exclusive Pacific species, while pan-Arctic species showed increased abundance with minimal ice cover. Abundance of oceanic Arctic species decreased across all regions, while opportunistic Arctic species exhibited fluctuating trends. Notably, Calanus glacialis, a pan-Arctic species, was the main contributor to the exceptionally high abundance of copepods in 2012 and is considered one of the earliest beneficiaries of sea ice retreat in the western Arctic. Compared to the advection from the Bering Sea, localized biological processes may have been a major driver of C. glacialis proliferation in 2012. In the present-day Chukchi Sea, which is still largely dominated by a benthic food chain, the proliferation of C. glacialis is likely to strengthen the pelagic pathway of carbon transfer and modify shelf ecosystem functioning.

Pelagic appendicularians, known for their rapid bloom capability, are important secondary producers and play essential roles in marine ecosystems. To assess the environmental adaptation of the most common appendicularian species Oikopleura dioica in Jiaozhou Bay, Shandong, China, its annual variations in abundance and body size were investigated monthly at 12 stations in 2011, and the relationship between somatic growth and gonadal development was compared with previously published laboratory data. Oikopleura dioica exhibited distinct seasonal abundance patterns, peaking in summer and autumn, particularly in the inner bay, reflecting its adaptation to the eutrophic conditions and high food availability. Compared to laboratory results, O. dioica in Jiaozhou Bay exhibited shorter body lengths, smaller gonad volumes, and earlier maturation at reduced body sizes, despite high natural chlorophyll-a concentration, suggesting that factors beyond food availability, such as resource competition and environmental stressors, may limit its growth in natural settings. Correlation analysis indicated that the somatic growth of natural O. dioica was primarily influenced by temperature, while gonadal development was related to chlorophyll-a concentration, and its population abundance was linked to food availability and the abundance of other zooplankton, such as copepods and jellyfish. It was suggested that the growth and recruitment of O. dioica were constrained by resource limitations in natural environments, further exacerbated by interactions with other zooplankton, including predation and competition. This study provides valuable data on the mechanisms underlying bio-environmental interactions and their spatiotemporal variations, offering critical insights into the ecological roles of appendicularians in marine ecosystems.

Bisphenol A (BPA), a known endocrine disruptor, is ubiquitous in various aquatic environments. Appendicularians are among the most abundant mesozooplankton populations and occupy a crucial niche in marine ecosystems. However, no toxicological data are available concerning the effects of BPA on this functional group. In this study, an evaluation of the toxicity of environmentally relevant levels of BPA (2.5-150 mu g/L) on the appendicularian Oikopleura dioica, including its morphology and transcriptome, was conducted. Our results demonstrated the high sensitivity of O. dioica to BPA, with a LC50 of 142 mu g/L. Exposure to 125 mu g/L BPA significantly inhibited the somatic growth, gonadal development and reproduction of individuals, whereas exposure to an environmentally safe concentration (2.5 mu g/L) affected female fecundity and fitness as well as male gene expression. The results of the transcriptomic analysis suggest that males were more sensitive to BPA stress at the molecular level. BPA exposure not only led to abnormal secretion of digestive enzymes and phospholipase A2, affecting the function of the digestive system and arachidonic acid but also significantly downregulated the expression of mRNAs related to enzymes involved in carbohydrate and energy metabolism in males. These findings suggest that the current safe environmental concentrations may not be safe.

Activation of Nrf2 by Keap1 alkylation plays a central role in anti-inflammatory therapy. However, activators of Nrf2 through alkylation of Keap1-Kelch domain have not been identified. Deoxynyboquinone (DNQ) is a natural small molecule discovered from marine actinomycetes. The current study was designed to investigate the anti-inflammatory effects and molecular mechanisms of DNQ via alkylation of Keap1. DNQ exhibited significant anti-inflammatory properties both in vitro and in vivo. The pharmacophore responsible for the anti-inflammatory properties of DNQ was determined to be the α, β-unsaturated amides moieties by a chemical reaction between DNQ and N-acetylcysteine. DNQ exerted anti-inflammatory effects through activation of Nrf2/ARE pathway. Keap1 was demonstrated to be the direct target of DNQ and bound with DNQ through conjugate addition reaction involving alkylation. The specific alkylation site of DNQ on Keap1 for Nrf2 activation was elucidated with a synthesized probe in conjunction with liquid chromatography-tandem mass spectrometry. DNQ triggered the ubiquitination and subsequent degradation of Keap1 by alkylation of the cysteine residue 489 (Cys489) on Keap1-Kelch domain, ultimately enabling the activation of Nrf2. Our findings revealed that DNQ exhibited potent anti-inflammatory capacity through α, β-unsaturated amides moieties active group which specifically activated Nrf2 signal pathway via alkylation/ubiquitination of Keap1-Kelch domain, suggesting the potential values of targeting Cys489 on Keap1-Kelch domain by DNQ-like small molecules in inflammatory therapies.

Regio- and chemoselective C-H activation at multi-positions of a single molecule is fascinating but chemically challenging. The homologous cytochrome P450 enzymes IkaD and CftA catalyze multiple C-H oxidations on the same polycyclic tetramate macrolactam (PoTeM) ikarugamycin, with distinct regio- and chemoselectivity. Herein we provide mechanistic understanding of their functional differences by solving crystal structures of IkaD and CftA in complex with ikarugamycin and unnatural substrates. Distinct conformations of the F/G region in IkaD and CftA are found to differentiate the orientation of PoTeM substrates, by causing different binding patterns with polar moieties to determine site selection, oxidation order, and chemoselectivity. Fine-tuning the polar subpocket altered the regioselectivity of IkaD, indicating that substrate re-orientation by mutating residues distal to the oxidation site could serve as an important method in future engineering of P450 enzymes.

The antibacterial agents deoxynybomycin (DNM) and nybomycin (NM) have a unique tetracyclic structure featuring an angularly fused 4-oxazoline ring. Here, we report the identification of key enzymes responsible for forming the 4-oxazoline ring in Embleya hyalina NBRC 13850 by comparative bioinformatics analysis of the biosynthetic gene clusters encoding structurally similar natural products DNM, deoxynyboquinone (DNQ), and diazaquinomycins (DAQs). The N-methyltransferase DnmS plays a crucial role in catalyzing the N-dimethylation of a tricyclic precursor prenybomycin to generate NM D; subsequently, the Fe(II)/α-ketoglutarate-dependent dioxygenase (Fe/αKGD) DnmT catalyzes the formation of a 4-oxazoline ring from NM D to produce DNM; finally, a second Fe/αKGD DnmU catalyzes the C-12 hydroxylation of DNM to yield NM. Strikingly, DnmT is shown to display unexpected functions to also catalyze the decomposition of the 4-oxazoline ring and the N-demethylation, thereby converting DNM back to prenybomycin, to putatively serve as a manner to control the intracellular yield of DNM. Structure modeling, site-directed mutagenesis, and quantum mechanics calculations provide mechanistic insights into the DnmT-catalyzed reactions. This work expands our understanding of the functional diversity of Fe/αKGDs in natural product biosynthesis.

In recent decades,environmental changes in the Arctic have aroused widespread concern around the world.To better understand ecology issues such as ecosystem dynamics,the Arctic and the subarctic regions were integrated as the"pan-Arctic"region.In this study,mesozooplankton were sampled from the Bering Sea shelf to the northern Chukchi Sea during the 10th Chinese National Arctic Research Expedition in 2019.Based on the species composition and abundance,three geographical communities were identified:the Bering Sea shelf community(BSS),the Bering Strait transitional community(BST),and the Chukchi Sea shelf community(CSS).The BSS was characterized by Bering Sea oceanic species such as Eucalanus bungii;the BST was mainly composed of the pan-Arctic distributed Calanus glacialis,meroplankton of benthos,and neritic species such as Centropages abdominalis;copepods,especially the copepodite of C.glacialis,were predominant in the CSS community.The BSS community structure was strongly affected by the inflow of Bering Shelf Water,while those of BST and CSS were determined by the recruitment of local species.The zooplankton community structure is influenced by both advection and environmental changes such as warming and a prolonged productivity period.Here,it was difficult to distinguish the changes induced by climate change from the effects of the Bering Sea Water.The key to solving this problem is the accumulation of comparable data,which requires continuous monitoring of key species such as C.glacialis and Calanus hyperboreus.

为全面了解黄海典型海区微微型浮游植物的季节变化特征,于2009年7月至2010年6月在北黄海獐子岛海域和2010年1～12月在南黄海胶州湾进行逐月调查采样,利用流式细胞仪检测了表层海水中微微型浮游植物(picophytoplankton)的丰度,包括聚球藻(Synechococcus,SYN)和微微型真核浮游植物(picoeukaryotes,PEUK),并分析了其与环境因子的关系.獐子岛海域和胶州湾SYN和PEUK全年广泛分布,獐子岛海域SYN丰度范围在0.05×103～120.00×103 cells/mL之间,丰度在秋季最高;胶州湾SYN丰度范围在0.02×103～61.80×103 cells/mL之间,丰度在夏季最高.獐子岛海域PEUK丰度范围在0.01×103～18.76×103 cells/mL之间,丰度在秋季最高;胶州湾PEUK丰度范围在0.25×103～95.57×103 cells/mL之间,丰度在春季最高.獐子岛海域微微型浮游植物丰度组成以SYN为主;而胶州湾以PEUK为主.PEUK是两海区微微型浮游植物生物量的主要贡献者.相关性分析结果表明,温度是影响两海区SYN丰度季节变化的最主要因素;影响PEUK季节分布的因素不完全一致,獐子岛海域PEUK丰度主要受温度调控;胶州湾PEUK丰度主要受温度和营养盐浓度影响.与已有研究比较,这两个海区的微微型浮游植物生物量对浮游植物生物量的贡献明显高于其他温带沿岸海域,预示微微型浮游植物在獐子岛海域和胶州湾生态系统中的重要作用,值得进一步深入研究.

Herbivore digestion in aquatic ecosystems is usually considered a method of nutrient repackaging rather than recycling, as recalcitrant and low-level nutrients are presumed for their egesta. We hypothesize that this opinion holds only for nutrients recycled by excretion and egestion, not for those elements recycled overwhelmingly by fecal decomposition. In this study, we compared the dissolution of biogenic silica (BSi), phosphorus (P) and iron (Fe) between two food items and fecal pellets of two marine invertebrates fed on artificial seawaters free of bacteria. Relative to raw food materials, the mass proportion in fecal pellets of BSi increased, while that of P and Fe decreased. During the 21 days of incubation, the total dissolution rate of BSi was 13.9–36.0 times higher in fecal pellets than food items, followed by P (1.5–4.2 times) and Fe (1.1–2.4 times). While the dissolution of BSi and Fe occurred mostly in the first few days, P was mostly released in the last ten days. Regarding BSi dissolution, a higher rate was observed in oyster Crassostrea gigas than the Echiuran Urechis unicinctus, but no significant difference was found between fecal pellets in either species under naturally available diatom food (Phaeodactylum tricornutum) and introduced terrestrial food (rice husk powder), respectively. Our results show direct evidence of digestion-associated nutrients mobilization. BSi dissolution after animal digestion may be similarly efficient to that caused by bacteria colonization in natural seawater.

A warm-water doliolid species Dolioletta gegenbauri (Uljanin, 1884) was firstly recorded in Jiaozhou Bay (JZB) during the autumn of 2019–2020. As a warm-water species, its native habitat lies in the East China Sea Shelf, >1000 km south of JZB. Distribution, abundance, stage composition, size frequency distribution, and relationships with environmental factors were studied. Both asexual and sexual reproduction stages were observed. Gonozooids generally dominated the population, indicating an active population development status. Abundance was significantly correlated to temperature. Water temperature in the two consecutive years was among the highest levels during the recent 3–4 decades. The continuous warming trends both in the China coastal seas and JZB likely expanded the biogeographic range. The sub branches of a boundary current, the Kuroshio Current, especially the Yellow Sea Warm Current, may play a central role during the northward extension. Moreover, its feeding, growth, reproduction, and recruitment could also be benefited from the neritic food environment. Finally, when the temperature dropped below 15 °C in the early winter, it disappeared in JZB. The seasonal expansion of D. gegenbauri in JZB could be facilitated by current transportation, warming, and the neritic environment.

The fungus strain SCSIO 40433 was isolated from an Arctic-derived glacier sediment sample and characterized as Tolypocladium cylindrosporum. A new compound, cylindromicin (1), and seven known secondary metabolites (2–8) were isolated from this strain. The chemical structures of these compounds were elucidated by comprehensive spectroscopic analyses. Cylindromicin (1) featured a 3,4-dihydro-2H-pyran skeleton. The absolute configuration of compound 1 was assigned via interpretation of key Nuclear Overhauser Effect Spectroscopy (NOESY) correlations and Electronic Circular Dichroism (ECD) calculation. Cylindromicin (1) exhibited significant tyrosinase inhibition activity. This study highlights Polar fungi as a potential resource for new bioactive natural products.

The use of bivalve aquaculture to mitigate eutrophication in coastal waters has been proposed for years. As nitrogen overenrichment is usually accompanied by comparative shortages in silicate and phosphate, bivalve cultivation integrated with artificial fertilization may exhibit better nitrogen removal performance than bivalve cultivation alone. During a 15-day mesocosm experiment in a nitrogen-eutrophicated, phosphate-limited coastal pond, the nitrogen fixation in oyster tissue under rice husk ash (RHA)1 fertilized conditions was 10 times higher than that in the oyster-only treatments with the same density. Meanwhile, the concentrations of dissolved inorganic nitrogen (DIN) and particulate nitrogen (PN) in the combined oyster-fertilization treatments decreased by 87.0% and 57.2%, respectively. Compared with the RHA fertilization treatments, the net DIN consumption was significantly lower and decreased with the oyster density in the oyster-only treatments. The dissolved N/Si ratio decreased from 1.44 to 1.01 and 0.93 in the control and fertilization treatments, respectively, whereas in the oyster-only treatments, it increased to 3.74 at low density and 29.15 at high density. Our results indicate that oyster cultivation can stimulate the regeneration of nitrogen in dissolved forms and intensify relative silicate shortages. The integration of RHA fertilization mediated silicate shortage and helped maintain a balanced dissolved N/Si ratio. Moreover, the combined oyster-RHA fertilization enhanced nitrogen removal efficiency and biomass accumulation and increased the feasibility of oyster cultivation as a cost-effective nitrogen reduction measure.

[背景]斑鸠霉素及其氧化衍生物属于多环特特拉姆酸大环内酰胺类化合物,具有良好的生物活性,挖掘更多新颖斑鸠霉素类似物具有重要意义.细胞色素P450氧化酶CftA被认为能催化斑鸠霉素的氧化反应,但未有相关体外实验数据的报道.[目的]通过体外生化实验鉴定氧化酶CftA的功能,并探索其催化斑鸠霉素氧化反应的机制.[方法]利用基因合成的方法直接克隆斑鸠霉素氧化酶基因cftA,于大肠杆菌中诱导表达后,纯化蛋白进行体外酶反应,利用高效液相色谱与高分辨质谱联用技术鉴定酶反应产物.[结果]在体外,氧化酶CftA催化斑鸠霉素生成一个新的氧化衍生物Hydroxyikarugamycin D和一个已知氧化衍生物Clifednamide A.[结论]进行了细胞色素P450氧化酶CftA的体外生化研究,证实其能特异性催化斑鸠霉素C29位的两步氧化反应,为进一步探索斑鸠霉素P450氧化酶的催化机制,以及通过生物酶催化拓展斑鸠霉素类多环特特拉姆酸大环内酰胺化合物的结构多样性奠定了基础.

A ctenophore Pleurobrachia globosa Moser, 1903, recognized as a warm water species, showed abrupt population rise since the year 2000 in a temperate bay-the Jiaozhou Bay (JZB), a coastal bay in northern China, > 1100 km north from the reported native habitat. Using hundreds of surveys in the JZB and the adjacent Yellow Sea (YS), we examined the population fluctuations over the recent 20 years, possible links between abundance and environmental factors, and the reproductive strategies. In the JZB, P. globosa mainly appeared from August to December each year, reaching the maximum abundance of 170 ind. m(-3) in August 2008. A general warming trend continues in the JZB during the recent two decades, with the alternating of warm and cool periods. Temperature is recognized as a primary driver of abundance variations, with significantly higher abundance levels in warmer years than in cooler years. The population uses either larval reproduction or adult reproduction almost exclusively in the JZB, with unknown mechanisms. High abundance can result from both reproductive strategies. Larval reproduction distinguishes itself from adult reproduction by significantly smaller parent size, egg size and clutch size, explaining the short-size dominated population in several surveys. Clutch size is positively related to body size and temperature. The geographical range of the YS population reached to similar to 39 degrees N in June 2014, indicating a northward expansion since the late 1990s, together with other evidences from the JZB and the Bohai Sea. While the successful establishment could be driven primarily by warming, lack of competitors and predators as well as the particular life history strategies also contributed. Issues of the vectors for introduction, local overwintering population, and regulatory mechanism of reproductive strategy need to be addressed in further studies.

Extracts from Antarctic-derived Penicillium chrysogenum CCTCC M 2020019 showed potent antibacterial bioactivities. We report herein the isolation of chrysonin (1), a new compound containing a pair of enantiomers 6S- and 6R-chrysonin (1a and 1b) featuring an unprecedented eight-membered heterocycle fused with a benzene ring. Compound 2, a mixture consisting of a new zwitterionic compound chrysomamide (2a) and N-[2-trans-(4-hydroxyphenyl) ethenyl] formamide (2b) in a ratio around 1 : 2.8, was isolated together with seven known compounds 3–9. Chemical structures of all compounds were determined by comprehensive spectroscopic analyses. The isolated compounds were evaluated for antimicrobial, cytotoxic and alpha-glucosidase inhibition activities. Chrysonin (1) showed moderate alpha-glucosidase inhibitory activity. The dominant product xanthocillin X (4) displayed potent inhibition activities against Gram-negative pathogens Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa with MIC values at 0.125 μg mL−1. Xanthocillins X (4) and Y1 (5) also showed significant cytotoxicities against four cancer cell lines with IC50 values ranging from 0.26 to 5.04 μM. This study highlights that microorganisms from polar regions are emerging as a new resource for the discovery of natural products combating human pathogens.

Dissolved inorganic nitrogen (DIN) enrichment accompanied by silicate deficiency in seawater can promote dinoflagellate growth over diatom growth and induce further negative ecological consequences. Here, we propose an easily exercisable method for silicate fertilization as a remedy of eutrophication. In the laboratory, rice husk ash (RHA) released silicate and phosphate in an atomic ratio range of 38-113 without a significant influence on DIN. During incubations of silicate-limited waters, low-dose fertilization increased the diatom/dinoflagellate ratio by 1-5 times. With the high-dose fertilizer addition, DIN, with an initial concentration of 7.63 +/- 0.95 mu moll(-1), was exhausted in three days, and the diatom abundance increased by 19 times on the 5th day. The silicate fertilization method presented here can be applied independently in eutrophicated waters for dinoflagellate suppression and dissolved nitrogen removal; this method could also work as a supplementary measure to existing nutrient (N, P) reduction and biomanipulation efforts.

Combinatorial biosynthesis of 5/5/6 type polycyclic tetramate macrolactams (PoTeMs) was achieved in an engineered ikarugamycin (5/6/5 type) producer by introducing a set of 5/5/6 type PoTeM biosynthetic genes from Streptomyces griseus. This study supports the idea that PoTeMs share a common polyene tetramate precursor generated by the hybrid polyketide synthase/nonribosomal peptide synthetase enzymes. The X-ray crystal structure of pactamide G (7) sets an example for resolving the absolute configuration of 5/5/6 type PoTeMs.

Gelatinous tunicates with rapid bloom capability are ubiquitous and important in marine ecosystems. To evaluate the rapid response of a most common appendicularian species, Oikopleura dioica, to fluctuating environmental conditions, spatio-temporal abundance, chlorophyll a concentration and body size was investigated twice a week at 5 stations in Jiaozhou Bay, a eutrophic and semi-closed embayment of China. The highest recorded O. dioica abundance was 28107 ind. m−3. Mature individuals attained body lengths ranging from 114.92 to 619.11μm. Compared with the body/gonad length relationship established in laboratory studies, the natural population in Jiaozhou Bay had greater gonad length at the same body length. The difference of gonad length between natural and laboratory specimens was -1.04–6.03μm for matures and 24.93–30.63μm for immatures at various food regimes. Body size in this study showed a significant positive correlation with chlorophyll a concentration of the size range 0.2–20μm. Considering that maturation at smaller body size and shorter generation time arising therefrom can result in higher intrinsic rates of natural population increase, it suggests that early maturation favors a rapid response of O. dioica to fleeting phytoplankton blooms. Although such response was limited to blooms of small size phytoplankton, it may help on recovery of micro-phytoplankton dominance in natural environments.