Discovery of Kebanmycins with Antibacterial and Cytotoxic Activities from the Mangrove-Derived Streptomyces sp. SCSIO 40068.

Mangrove derived actinomycetes are a rich reservoir of bioactive natural products and play important roles in pharmaceutical chemistry. In a screen of actinomycetes from mangrove rhizosphere sedimental environments, the isolated strain Streptomyces sp. SCSIO 40068 displayed strong antibacterial activity. Further fractionation of the extract yielded four new compounds kebanmycins A-D (1-4) and two known analogues FD-594 (5) and the aglycon (6). The structures of 1-6 were determined based on extensive spectroscopic data and single-crystal X-ray diffraction analysis. 1-3 featured a fused pyranonaphthaxanthene as an integral part of a 6/6/6/6/6/6 polycyclic motif, and showed bioactivity against a series of Gram-positive bacteria and cytotoxicity to several human tumor cells. In addition, the kebanmycins biosynthetic gene cluster (keb) was identified in Streptomyces sp. SCSIO 40068, and KebMT2 was biochemically characterized as a tailoring sugar-O-methyltransferase, leading to a proposed biosynthetic route to 1-6. This study paves the way to further investigate 1 as a potential lead compound.

Discovery and Biosynthesis of Cihanmycins Reveal Cytochrome P450-Catalyzed Intramolecular C-O Phenol Coupling Reactions.

Cinnamoyl-containing nonribosomal peptides (CCNPs) constitute a unique family of natural products. The enzyme mechanism for the biaryl phenol coupling reaction of the bicyclic CCNPs remains unclear. Herein, we report the discovery of two new arabinofuranosylated bicyclic CCNPs cihanmycins (CHMs) A (1) and B (2) from Amycolatopsis cihanbeyliensis DSM 45679 and the identification of the CHM biosynthetic gene cluster (cih BGC) by heterologous expression in Streptomyces lividans SBT18 to afford CHMs C (3) and D (4). The structure of 1 was confirmed by X-ray diffraction analysis. Three cytochrome P450 enzyme (CYP)-encoding genes cih26, cih32, and cih33 were individually inactivated in the heterologous host to produce CHMs E (5), F (6), and G (7), respectively. The structures of 5 and 6 indicated that Cih26 was responsible for the hydroxylation and epoxidation of the cinnamoyl moiety, and Cih32 should catalyze the ß-hydroxylation of three amino acid residues. Cih33 and its homologues DmlH and EpcH were biochemically verified to convert CHM G (7) with a monocyclic structure to a bicyclic skeleton of CHM C (3) through an intramolecular C-O phenol coupling reaction. The substrate 7-bound crystal structure of DmlH not only established the structure of 7, which was difficult for NMR analysis for displaying anomalous splitting signals, but also provided the binding mode of macrocyclic peptides recognized by these intramolecular C-O coupling CYPs. In addition, computational studies revealed a water-mediated diradical mechanism for the C-O phenol coupling reaction. These findings have shed important mechanistic insights into the CYP-catalyzed phenol coupling reactions.

A ratiometric fluorescence and colorimetry dual-signal sensing strategy based on o-phenylenediamine and AuNCs for determination of Cu2+ and glyphosate.

A ratiometric fluorescence sensing strategy has been developed for the determination of Cu2+ and glyphosate with high sensitivity and specificity based on OPD (o-phenylenediamine) and glutathione-stabilized gold nanoclusters (GSH-AuNCs). Water-soluble 1.75-nm size GSH-AuNCs with strong red fluorescence and maximum emission wavelength at 682 nm were synthesized using GSH as the template. OPD was oxidized by Cu2+, which produced the bright yellow fluorescence oxidation product 2,3-diaminophenazine (DAP) with a maximum fluorescence emission peak at 570 nm. When glyphosate existed in the system, the chelation between glyphosate and Cu2+ hindered the formation of DAP and reduced the fluorescence intensity of the system at the wavelength of 570 nm. Meanwhile, the fluorescence intensity at the wavelength of 682 nm remained basically stable. It exhibited a good linear relationship towards Cu2+ and glyphosate in water in the range 1.0-10 µM and 0.050-3.0 µg/mL with a detection limit of 0.547 µM and 0.0028 µg/mL, respectively. The method was also used for the semi-quantitative determination of Cu2+ and glyphosate in water by fluorescence color changes visually detected by the naked eyes in the range 1.0-10 µM and 0.30-3.0 µg/mL, respectively. The sensing strategy showed higher sensitivity, more obvious color changes, and better disturbance performance, satisfying with the detection demands of Cu2+ and glyphosate in environmental water samples. The study provides a reliable detection strategy in the environment safety fields.

Large Non-Hysteretic Volume Magnetostriction in a Strong and Ductile High-Entropy Alloy.

Rapid development of smart technologies poses a big challenge for magnetostrictive materials, which should not only permit isotropic and hysteresis-free actuation (i.e., non-hysteretic volume change) in magnetic fields, but also have high strength and high ductility. Unfortunately, the magnetostriction from self-assembly of ferromagnetic domains is volume-conserving; the volume magnetostriction from field-induced first-order phase transition has large intrinsic hysteresis; and most prototype magnetostrictive materials are intrinsically brittle. Here we report a magnetic high-entropy alloy (HEA) Fe35Co35Al10Cr10Ni10 that can rectify these challenges, exhibiting an unprecedented combination of large non-hysteretic volume magnetostriction, high tensile strength and large elongation strain, over a wide working temperature range from room temperature down to 100 K. Its exceptional properties stem from a dual-phase microstructure, where the face-centered-cubic (FCC) matrix phase with nano-scale compositional and structural fluctuations can enable a magnetic-field-induced transition from low-spin small-volume state to high-spin large-volume state, and the ordered body-centered-cubic (BCC) B2 phase contributes to mechanical strengthening. The present findings may provide insights into designing unconventional and technologically-important magnetostrictive materials. This article is protected by copyright. All rights reserved.

Replenishment of mitochondrial Na+ and H+ by ionophores potentiates cutaneous wound healing in diabetes.

Diabetic foot ulcer (DFU) is a highly morbid complication in patients with diabetes mellitus, necessitating the development of innovative pharmaceuticals to address unmet medical needs. Sodium ion (Na+) is a well-established mediator for membrane potential and osmotic equilibrium. Recently, Na+ transporters have been identified as a functional regulator of regeneration. However, the role of Na+ in the intricate healing process of mammalian wounds remains elusive. Here, we found that the skin wounds in hyponatremic mice display a hard-to-heal phenotype. Na+ ionophores that were employed to increase intracellular Na+ content could facilitate keratinocyte proliferation and migration, and promote angiogenesis, exhibiting diverse biological activities. Among of them, monensin A emerges as a promising agent for accelerating the healing dynamics of skin wounds in diabetes. Mechanistically, the elevated mitochondrial Na+ decelerates inner mitochondrial membrane fluidity, instigating the production of reactive oxygen species (ROS), which is identified as a critical effector on the monensin A-induced improvement of wound healing. Concurrently, Na+ ionophores replenish H+ to the mitochondrial matrix, causing an enhancement of mitochondrial energy metabolism to support productive wound healing programs. Our study unfolds a new role of Na+, which is a pivotal determinant in wound healing. Furthermore, it directs a roadmap for developing Na+ ionophores as innovative pharmaceuticals for treating chronic dermal wounds in diabetic patients.

Small molecule deoxynyboquinone triggers alkylation and ubiquitination of Keap1 at Cys489 on Kelch domain for Nrf2 activation and inflammatory therapy.

Activation of nuclear factor erythroid 2-related factor 2 (Nrf2) by Kelch-like ECH-associated protein 1 (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, ß-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, ß-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.

An Enzymatic Carbon-Carbon Bond Cleavage and Aldol Reaction Cascade Converts an Angular Scaffold into the Linear Tetracyclic Core of Ochraceopones.

Meroterpenoids of the ochraceopones family featuring a linear tetracyclic scaffold exhibit exceptional antiviral and anti-inflammatory activities. The biosynthetic pathway and chemical logic to generate this linear tetracycle, however, remain unknown. In this study, we identified and characterized all biosynthetic enzymes to afford ochraceopones and elucidated the complete biosynthetic pathway. We demonstrated that the linear tetracyclic scaffold of ochraceopones was derived from an angular tetracyclic precursor. A multifunctional cytochrome P450 OchH was validated to catalyze the free-radical-initiated carbon-carbon bond cleavage of the angular tetracycle. Then, a new carbon-carbon bond was verified to be constructed using a new aldolase OchL, which catalyzes an intramolecular aldol reaction to form the linear tetracycle. This carbon-carbon bond fragmentation and aldol reaction cascade features an unprecedented strategy for converting a common angular tetracycle to a distinctive linear tetracyclic scaffold in meroterpenoid biosynthesis.

Epidemiology and Molecular Characterization of Zoonotic Gastrointestinal Protozoal Infection in Zoo Animals in China.

Zoo animals, harboring zoonotic gastrointestinal protozoal diseases, pose potential hazards to the safety of visitors and animal keepers. This study involved the collection and examination of 400 fresh fecal samples from 68 animal species, obtained from five zoos. The aim of this study was to determine the occurrence, genetic characteristics, and zoonotic potential of common gastrointestinal protists. PCR or nested PCR analysis was conducted on these samples to detect four specific parasites: Cryptosporidium spp., Giardia duodenalis, Enterocytozoon bieneusi, and Blastocystis spp. The overall prevalence of Cryptosporidium spp was 0.5% (2/400), G. duodenalis was 6.0% (24/400), Blastocystis spp. was 24.5% (98/400), and E. bieneusi was 13.5% (54/400). G. duodenalis, Blastocystis spp., and E. bieneusi were detected in all of the zoos, exhibiting various zoonotic genotypes or subtypes. G. duodenalis-positive samples exhibited three assemblages (D, E, and B). Blastocystis spp. subtypes (ST1, ST2, ST3, ST4, ST5, ST8, ST10, ST13, and ST14) and one unknown subtype (ST) were identified. A total of 12 genotypes of E. bieneusi were identified, including SC02, BEB6, Type IV, pigEBITS 7, Peru8, PtEb IX, D, CD9, EbpC, SCBB1, CM4, and CM7. Moreover, significant differences in the positive rates among different zoos were observed (p < 0.01). The findings indicate that zoo animals in China are affected by a range of intestinal protozoa infections. Emphasizing molecular identification for specific parasite species or genotypes is crucial for a better understanding of the zoonotic risk. Preventing and controlling parasitic diseases in zoos is not only vital for zoo protection and management but also holds significant public health implications.

Discovery of Aburatubolactams Reveals Biosynthetic Logic for Distinct 5/5-Type Polycyclic Tetramate Macrolactams.

A known polycyclic tetramate macrolactam (aburatubolactam C, 3) and three new ones (aburatubolactams D-F, 4-6, respectively) were isolated from the marine-derived Streptomyces sp. SCSIO 40070. The absolute configuration of 3 was established by X-ray analysis. A combinatorial biosynthetic approach unveiled biosynthetic enzymes dictating the formation of distinct 5/5-type ring systems (such as C7-C14 cyclization by AtlB1 in 5 and C6-C13 cyclization by AtlB2 in 6) in aburatubolactams.

Expanding the Chemical Diversity of Grisechelins via Heterologous Expression.

Thiazole scaffold-based small molecules exhibit a range of biological activities and play important roles in drug discovery. Based on bioinformatics analysis, a putative biosynthetic gene cluster (BGC) for thiazole-containing compounds was identified from Streptomyces sp. SCSIO 40020. Heterologous expression of this BGC led to the production of eight new thiazole-containing compounds, grisechelins E, F, and I-N (1, 2, 5-10), and two quinoline derivatives, grisechelins G and H (3 and 4). The structures of 1-10, including their absolute configurations, were elucidated by HRESIMS, NMR spectroscopic data, ECD calculations, and single-crystal X-ray diffraction analysis. Grisechelin F (2) is a unique derivative, distinguished by the presence of a salicylic acid moiety. The biosynthetic pathway for 2 was proposed based on bioinformatics analysis and in vivo gene knockout experiments. Grisechelin E (1) displayed moderate antimycobacterial activity against Mycobacterium tuberculosis H37Ra (MIC of 8 µg mL-1).

Benchmark for welding gun fault prediction with multivariate time series data.

In the automotive industry, machinery failures of the resistance spot welding (RSW) guns would interrupt the manufacturing lines and cause unplanned downtime, potentially resulting in a significant loss of production and reliability. Predicting the machinery failures of the RSW gun can provide more scientific strategies for predictive maintenance and decision-making. However, fault prediction of RSW guns has become increasingly challenging due to their complex behavior and data variability. In this paper, we created a benchmark dataset and proposed welding gun fault prediction benchmarks to aid in the development of machine learning approaches toward welding gun fault prediction. The dataset was collected at the Body-Shop (BS) of BMW Brilliance Automotive Ltd. from different components of hundreds of RSW guns to capture the patterns and trends before welding errors with historical data. Then we provide state-of-the-art machine learning (ML) benchmarks on time series forecasting methods in a welding gun fault prediction use case. This study will provide insights for time series forecasting while enabling ML researchers to contribute towards the fault prediction of the RSW guns.

Non-enzymatic synthesis of C-methylated fluostatins: discovery and reaction mechanism.

Two C-methylated fluostatins (FSTs) B3 (1) and B4 (2) were synthesized from flavin-mediated nonenzymatic epoxide ring-opening reactions of FST C. The structures of 1 and 2 were elucidated by HRESIMS, NMR, and ECD spectroscopic analyses. A subsequent 13C labeling study demonstrated that the C-methyl groups of 1 and 2 were derived from DMSO and enabled the mechanistic proposal of a nonenzymatic C-methylation.

CCNI2 promotes pancreatic cancer through PI3K/AKT signaling pathway.

Globally, pancreatic cancer is recognized as one of the deadliest malignancies that lacks effective targeted therapies. This study aims to explore the role of cyclin I-like protein (CCNI2), a homolog of cyclin I (CCNI), in the progression of pancreatic cancer, thereby providing a theoretical basis for its treatment. Firstly, the expression of CCNI2 in pancreatic cancer tissues was determined through immunohistochemical staining. The biological role of CCNI2 in pancreatic cancer cells was further assessed using both in vitro and in vivo loss/gain-of-function assays. Our data revealed that CCNI2 expression was abnormally elevated in pancreatic cancer, and clinically, increased CCNI2 expression generally correlated with reduced overall survival. Functionally, CCNI2 contributed to the malignant progression of pancreatic cancer by promoting the proliferation and migration of tumor cells. Consistently, in vivo experiments verified that CCNI2 knockdown impaired the tumorigenic ability of pancreatic cancer cells. Moreover, the addition of phosphatidylinositol 3-kinase (PI3K) inhibitors could partially reverse the promoting effect of CCNI2 on the malignant phenotypes of pancreatic cancer cells. CCNI2 promoted pancreatic cancer through PI3K/protein kinase B (AKT) signaling pathway, indicating its potential as a prognostic marker and therapeutic target for pancreatic cancer.

Public Knowledge and Awareness of Anesthesiology and Anesthesiologists in China: A Cross-Sectional National Survey of 1 Million Participants.

BACKGROUND: In the past 20 years, anesthesiology has become one of the most advanced specialties and has undergone rapid development. However, public awareness regarding anesthesiology and anesthesiologists is limited, especially in developing countries. It is important for anesthesiologists to make the public aware of their role during surgery. Therefore, a nationwide survey was set up to investigate public awareness of anesthesiology and anesthesiologists in China. METHOD: A cross-sectional nationwide survey was performed from June 2018 to June 2019 in 34 provinces, municipalities, and autonomous regions across China and an overseas region. The questionnaires of the survey were divided into 2 main parts: general items and research items. General items included the demographic characteristics of the participants; research items consisted of 10 questions about the public's awareness of anesthesiologists and anesthesiology. Data quality control was undertaken by the investigation committee throughout the survey process. RESULTS: The nationwide survey enrolled 1,001,279 participants (male, 40.7%). We found that most of the participants regarded anesthesiologists as doctors. However, public knowledge of anesthesiologists' work and duties during surgery was quite low, with correct response rate ranging from 16.5% to 52.9%, and anesthesiologist responsibilities were often mistakenly attributed to surgeons or nurses. It is disappointing that more than half of participants still thought that, once the patient fell asleep after receiving anesthetics, the anesthesiologist could leave the operating room. Finally, the correct response rate was positively correlated with the economic levels of the regions. CONCLUSIONS: Public awareness regarding anesthesiology and anesthesiologists in China remains inadequate. Due to the biases and characteristics of the participants, the actual situation of the general Chinese public is likely even worse than reflected here. Therefore, extensive measures should be undertaken to improve public knowledge of anesthesiology and anesthesiologists.

Naturally Occurring and Widespread Resistance to Bioactive Natural Products.

Naturally occurring resistances diminish the effectiveness of antibiotics, and present significant challenges to human health. Human activities are usually considered as the main drivers of the dissemination of antibiotic resistance, however, the origin of the clinical antibiotic resistance can be traced to the environmental microbes, and the clinically relevant resistance determinants have already pre-existed in nature before the antibiotics come into clinic. In this concept, we present the naturally occurring and widespread resistance determinants recently discovered during the biosynthesis study of bioactive compounds. These widely prevalent resistances in environmental microbes, including antibiotic producers and non-producers, advance the understanding of the origin of resistance, and provide prediction for the clinically relevant resistance to aid in the rational design of more effective drug analogues to combat resistance.

Deciphering Deoxynybomycin Biosynthesis Reveals Fe(II)/α-Ketoglutarate-Dependent Dioxygenase-Catalyzed Oxazoline Ring Formation and Decomposition.

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.

A Mechanistic Understanding of the Distinct Regio- and Chemoselectivity of Multifunctional P450s by Structural Comparison of IkaD and CftA Complexed with Common Substrates.

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.

Individualised positive end-expiratory pressure titrated intra-operatively by electrical impedance tomography optimises pulmonary mechanics and reduces postoperative atelectasis: A randomised controlled trial.

BACKGROUND: A protective intra-operative lung ventilation strategy has been widely recommended for laparoscopic surgery. However, there is no consensus regarding the optimal level of positive end-expiratory pressure (PEEP) and its effects during pneumoperitoneum. Electrical impedance tomography (EIT) has recently been introduced as a bedside tool to monitor lung ventilation in real-time. OBJECTIVE: We hypothesised that individually titrated EIT-PEEP adjusted to the surgical intervention would improve respiratory mechanics during and after surgery. DESIGN: Randomised controlled trial. SETTING: First Medical Centre of Chinese PLA General Hospital, Beijing. PATIENTS: Seventy-five patients undergoing robotic-assisted laparoscopic hepatobiliary and pancreatic surgery under general anaesthesia. INTERVENTIONS: Patients were randomly assigned 2 : 1 to individualised EIT-titrated PEEP (PEEPEIT; n = 50) or traditional PEEP 5 cmH2O (PEEP5 cmH2O; n = 25). The PEEPEIT group received individually titrated EIT-PEEP during pneumoperitoneum. The PEEP5 cmH2O group received PEEP of 5 cmH2O during pneumoperitoneum. MAIN OUTCOME MEASURES: The primary outcome was respiratory system compliance during laparoscopic surgery. Secondary outcomes were individualised PEEP levels, oxygenation, respiratory and haemodynamic status, and occurrence of postoperative pulmonary complications (PPCs) within 7 days. RESULTS: Compared with PEEP5 cmH2O, patients who received PEEPEIT had higher respiratory system compliance (mean values during surgery of 44.3 ±â€Š11.3 vs. 31.9 ±â€Š6.6, ml cmH2O-1; P < 0.001), lower driving pressure (11.5 ±â€Š2.1 vs. 14.0 ±â€Š2.4 cmH2O; P < 0.001), better oxygenation (mean PaO2/FiO2 427.5 ±â€Š28.6 vs. 366.8 ±â€Š36.4; P = 0.003), and less postoperative atelectasis (19.4 ±â€Š1.6 vs. 46.3 ±â€Š14.8 g of lung tissue mass; P = 0.003). Haemodynamic values did not differ significantly between the groups. No adverse effects were observed during surgery. CONCLUSION: Individualised PEEP by EIT may improve intra-operative pulmonary mechanics and oxygenation without impairing haemodynamic stability, and decrease postoperative atelectasis. TRIAL REGISTRATION: Chinese Clinical Trial Registry (www.chictr.org.cn) identifier: ChiCTR2100045166.

The Application of the Generalized Additive Model to Represent Macrobenthos near Xiaoqing Estuary, Laizhou Bay.

Macrobenthos is widely used as an indicator of ecological health in marine monitoring and assessment. The present study aimed to characterize the interrelationships between the distribution of the macrobenthos community and environmental factors near Xiaoqing Estuary, Laizhou Bay. Responses of species richness to environmental factors were studied using the generalized additive model (GAM) and the Margalef diversity index (dM) as indicators of species diversity instead of individual indicator species. Six factors were selected in the optimal model by stepwise regression: sediment factors (organic matter, phosphate, nitrate nitrogen, and ammonium nitrogen) and water factors (salinity, and ammonium nitrogen). The response curves generated by the GAM showed a unimodal relationship among taxa diversity, salinity in water, and sediment organic matter. dM was positively correlated with ammonium nitrogen in water and was negatively correlated with phosphate in the sediment. The model optimized by forward stepwise optimization explained 92.6% of the Margalef diversity index with a small residual (2.67). The model showed good performance, with the measured dM strongly correlated with the predicted dM (Pearson R2 = 0.845, p < 0.05). The current study examined the combined influence of multiple eco-factors on macrobenthos, and the Margalef diversity index of macrobenthos was predicted by the GAM model in a salinity-stressed estuary.

Discovery of Tetronate-Containing Kongjuemycins from a Coral-Associated Actinomycete and Elucidation of Their Biosynthetic Origin.

Tetronate antibiotics make up a growing family of natural products with a wide variety of biological activities. Herein, we report four new tetronates kongjuemycins (KJMs, 5-8) from a coral-associated actinomycete Pseudonocardia kongjuensis SCSIO 11457, and the identification and characterization of the KJM biosynthetic gene cluster (kjm) by heterologous expression, comparative genomic analysis, isotope labeling, and gene knockout studies. The biosynthesis of KJMs is demonstrated to harness diverse precursors from primary metabolism for building secondary metabolites.