Composition, diel dynamic and biotic-abiotic interaction of marine neustonic zooplankton in the oligotrophic South China Sea.

Neuston, situated at the air-sea interface, stands as a crucial frontier in the realm of the global warming. Despite its unique habitat, there remains a need to substantiate the composition, diel dynamic and biotic-abiotic interaction of neustonic zooplankton in the tropical seas. In this study, we present rare observational data on neustonic zooplankton (0-20 cm) in the oligotrophic tropical South China Sea (SCS) during the summer of 2022. A total of eighteen samples were collected and analyzed, revealing the presence of fourteen taxa from eight phyla. The most prevalent group was Cypridina, accounting for 33.7% of the total abundance, followed by copepods (29.0%) and jellyfish (10.9%). Within copepods, the genus Pontella exhibited the highest relative abundance (38.0%). Additionally, each neuston taxon displayed unique diel distribution patterns. Cypridina was the most abundant taxon during the night (40.4%), while it shifted to copepod dominance during the day (50.4%). Among copepods, genus Pontella and larvae were dominant groups at night (44.7%) and during the day (30.0%), respectively. Moreover, a multivariate biota-environment analysis demonstrated that temperature, pH, dissolved oxygen and Si(OH)4 significantly impacted neuston composition. Notably, both jellyfish and sea snails showed a significant positive correlation with temperature, suggesting their potential dominance in the neuston community in response to future global warming in the oligotrophic tropical seas. This study lays a robust foundation for recognizing the neuston community in the oceanic SCS, and helps evaluate the long-term risks to neuston habitats under climate changes.

Inoculation with plant growth-promoting rhizobacteria improves seagrass Thalassia hemprichii photosynthesis performance and shifts rhizosphere microbiome.

Plant growth-promoting rhizobacteria (PGPR) inoculation is a crucial strategy for maintaining the sustainability of agriculture and presents a promising solution for seagrass ecological restoration in the face of disturbances. However, the possible roles and functions of PGPRs in the seagrass rhizosphere remain unclear. Here, we isolated rhizosphere bacterial strains from both reef and coastal regions and screened two PGPR isolates regarding their in vivo functional traits. Subsequently, we conducted microcosm experiments to elucidate how PGPR inoculation affected seagrass photosynthesis and shape within each rhizosphere microbiome. Both screened PGPR strains, Raoultella terrigena NXT28 and Bacillus aryabhattai XT37, excelled at expressing a specific subset of plant-beneficial functions and increased the photosynthetic rates of the seagrass host. PGPR inoculation not only decreased the abundance of sulfur-cycling bacteria, it also improved the abundance of putative iron-cycling bacteria in the seagrass rhizosphere. Strain XT37 successfully colonized the seagrass rhizosphere and displayed a leading role in microbial network structure. As a nitrogen-fixing bacteria, NXT28 showed potential to change the microbial nitrogen cycle with denitrification in the rhizosphere and alter dissimilatory and assimilatory nitrate reduction in bulk sediment. These findings have implications for the development of eco-friendly strategies aimed at exploiting microbial communities to confer sulfide tolerance in coastal seagrass ecosystem.

Latitudinal pronounced variations in tintinnid (Ciliophora) community at surface waters from the South China Sea to the Yellow Sea: Oceanic-to-neritic species shift, biotic-abiotic interaction and future prediction.

The oceanic-to-neritic species shift of microzooplanktonic tintinnids and their interaction with relevant abiotic variables are two crucial processes in the marine ecosystem. However, these processes remain poorly documented in China's marginal seas. In the summer of 2022, we investigated the community structure of pelagic tintinnids in surface waters from the South China Sea (SCS) to the Yellow Sea (YS), passing through the East China Sea (ECS). A number of 58 species from 23 genera were identified, with 36 and 22 species belonging to oceanic and neritic genera, respectively. The abundance proportion of oceanic and neritic genera exhibited a decreasing and increasing trend, respectively, from the SCS to YS. Furthermore, four distinctive tintinnid community groups were classified based on cluster analysis using tintinnid species and abundance data, and the position of southern Taiwan Strait was identified as the "Shift Point" for oceanic-to-neritic species dominance. The top two tintinnid species in each group showed distinct variations in body size. Additionally, multivariate biotic-abiotic statistical analyses revealed that temperature determined tintinnid species richness, while temperature, salinity, Si(OH)4, and Chl a determined tintinnid abundance. Our study provides a substantial foundation for recognizing the oceanic-to-neritic species shift of tintinnids in the China's marginal seas, and highlights the role of biotic-abiotic factors in driving biogeochemical fluxes and the potential response of microzooplankton to future climate change.

Insights into the structure of the pelagic microbial food web in the oligotrophic tropical Western Pacific: Examining trophic interactions and relationship with abiotic variables.

Microbial food webs (MFW) play an indispensable role in marine pelagic ecosystem, yet their composition and response to abiotic variables were poorly documented in the oligotrophic tropical Western Pacific. During winter of 2015, we conducted a survey to examine key components of MFW, including Synechococcus, Prochlorococcus, picoeukaryotes, heterotrophic prokaryotes (HP), heterotrophic/pigmented nanoflagellates and ciliates, across water column from surface to 2000 m. Each MFW component exhibited unique vertical distribution pattern, with abundance ratio varying over six and three orders of magnitude across Pico/Microplankton (1.6 ± 1.0 × 106) and Nano/Microplankton (3.2 ± 2.8 × 103), respectively. Furthermore, HP was main component for MFW in the bathypelagic (>1000 m) zone. Multivariate biota-environment analysis demonstrated that environmental variables, particularly temperature, significantly impacted MFW composition, suggesting that bottom-up control (resource availability) dominated the water column. Our study provides benchmark information for future environmental dynamics forcing on MFW in the oligotrophic tropical seas.

DeepAIR: A deep learning framework for effective integration of sequence and 3D structure to enable adaptive immune receptor analysis.

Structural docking between the adaptive immune receptors (AIRs), including T cell receptors (TCRs) and B cell receptors (BCRs), and their cognate antigens are one of the most fundamental processes in adaptive immunity. However, current methods for predicting AIR-antigen binding largely rely on sequence-derived features of AIRs, omitting the structure features that are essential for binding affinity. In this study, we present a deep learning framework, termed DeepAIR, for the accurate prediction of AIR-antigen binding by integrating both sequence and structure features of AIRs. DeepAIR achieves a Pearson's correlation of 0.813 in predicting the binding affinity of TCR, and a median area under the receiver-operating characteristic curve (AUC) of 0.904 and 0.942 in predicting the binding reactivity of TCR and BCR, respectively. Meanwhile, using TCR and BCR repertoire, DeepAIR correctly identifies every patient with nasopharyngeal carcinoma and inflammatory bowel disease in test data. Thus, DeepAIR improves the AIR-antigen binding prediction that facilitates the study of adaptive immunity.

Explore the dominant factor in prime editing via a view of DNA processing.

Prime editing is a revolutionary gene-editing method that is capable of introducing insertions, deletions and base substitutions into the genome. However, the editing efficiency of Prime Editor (PE) is limited by the DNA repair process. Here, we show that overexpression of the flap structure-specific endonuclease 1 (FEN1) and the DNA ligase 1 (LIG1) increases the efficiency of prime editing, which is similar to the dominant negative mutL homolog 1 (MLH1dn). In addition, MLH1 is still the dominant factor over FEN1 and LIG1 in prime editing. Our results help to further understand the relationship of proteins involved in prime editing and envisage future directions for the development of PE.

SC-AIR-BERT: a pre-trained single-cell model for predicting the antigen-binding specificity of the adaptive immune receptor.

Accurately predicting the antigen-binding specificity of adaptive immune receptors (AIRs), such as T-cell receptors (TCRs) and B-cell receptors (BCRs), is essential for discovering new immune therapies. However, the diversity of AIR chain sequences limits the accuracy of current prediction methods. This study introduces SC-AIR-BERT, a pre-trained model that learns comprehensive sequence representations of paired AIR chains to improve binding specificity prediction. SC-AIR-BERT first learns the 'language' of AIR sequences through self-supervised pre-training on a large cohort of paired AIR chains from multiple single-cell resources. The model is then fine-tuned with a multilayer perceptron head for binding specificity prediction, employing the K-mer strategy to enhance sequence representation learning. Extensive experiments demonstrate the superior AUC performance of SC-AIR-BERT compared with current methods for TCR- and BCR-binding specificity prediction.

Hypoxia and warming take sides with small marine protists: An integrated laboratory and field study.

Hypoxia and ocean warming are two mounting global environmental threats influencing marine ecosystems. However, the interactive effects of rising temperature and depleted dissolved oxygen (DO) on marine protists remains unknown. Here, we conducted a series of laboratory experiments on four protozoa with distinct cell sizes to investigate the combined effects of temperature (19, 22, 25, 28, and 31 °C) and oxygen availability (hypoxia, 2 mg DO L-1 and normoxia, 7 mg DO L-1) on their physiological performances (i.e., growth, ingestion, and respiration rates). The hypoxia-induced inhibition in three physiological rates increased with the biovolume of the protists. As the larger surface area to volume (SA/V) quotients of smaller protists facilitate higher capabilities of oxygen absorption and utilization, the smaller protists suffered less inhibitions induced by hypoxia. Moreover, the hypoxia-induced inhibition in physiological rates was exacerbated by increasing temperature, which can be verified by the reductions in the temperature sensitivities (represented by the activation energy, E). These results suggest that hypoxia could lead to a shift of protistan community with enhanced domination of small protists, and warming could exacerbate such a trend. We further examined our laboratory results in the Pearl River Estuary, where extensive bottom hypoxia often occurs in summer. We found the mean protist biovolume in hypoxic waters was significantly lower than that at normal stations. Also, the mean protist biovolume decreased with declining DO concentration and rising temperature, indicating the interactive effect of temperature and oxygen availability. Collectively, we suggest that hypoxia could cause a higher proportion of small-sized cells in the marine protistan community, and the projected ocean warming could intensify the tendency, which could undermine the capacity of oceanic carbon sequestration.

High Microeukaryotic Diversity in the Cold-Seep Sediment.

Microeukaryotic diversity, community structure, and their regulating mechanisms remain largely unclear in chemosynthetic ecosystems. Here, using high-throughput sequencing data of 18S rRNA genes, we explored microeukaryotic communities from the Haima cold seep in the northern South China Sea. We compared three distinct habitats: active, less active, and non-seep regions, with vertical layers (0-25 cm) from sediment cores. The results showed that seep regions harbored more abundant and diverse parasitic microeukaryotes (e.g., Apicomplexa and Syndiniales) as indicator species, compared to nearby non-seep region. Microeukaryotic community heterogeneity was larger between habitats than within habitat, and greatly increased when considering molecular phylogeny, suggesting the local diversification in cold-seep sediments. Microeukaryotic α-diversity at cold seeps was positively increased by metazoan richness and dispersal rate of microeukaryotes, while its ß-diversity was promoted by heterogeneous selection mainly from metazoan communities (as potential hosts). Their combined effects led to the significant higher γ-diversity (i.e., total diversity in a region) at cold seeps than non-seep regions, suggesting cold-seep sediment as a hotspot for microeukaryotic diversity. Our study highlights the importance of microeukaryotic parasitism in cold-seep sediment and has implications for the roles of cold seep in maintaining and promoting marine biodiversity.

Disentangling the Functional Role of Fungi in Cold Seep Sediment.

Cold seeps are biological oases of the deep sea fueled by methane, sulfates, nitrates, and other inorganic sources of energy. Chemolithoautotrophic bacteria and archaea dominate seep sediment, and their diversity and biogeochemical functions are well established. Fungi are likewise diverse, metabolically versatile, and known for their ability to capture and oxidize methane. Still, no study has ever explored the functional role of the mycobiota in the cold seep biome. To assess the complex role of fungi and fill in the gaps, we performed network analysis on 147 samples to disentangle fungal-prokaryotic interactions (fungal 18S and prokaryotic 16S) in the Haima cold seep region. We demonstrated that fungi are central species with high connectivity at the epicenter of prokaryotic networks, reduce their random-attack vulnerability by 60%, and enhance information transfer efficiency by 15%. We then scavenged a global metagenomic and metatranscriptomic data set from 10 cold seep regions for fungal genes of interest (hydrophobins, cytochrome P450s, and ligninolytic family of enzymes); this is the first study to report active transcription of 2,500+ fungal genes in the cold seep sediment. The genera Fusarium and Moniliella were of notable importance and directly correlated with high methane abundance in the sulfate-methane transition zone (SMTZ), likely due to their ability to degrade and solubilize methane and oils. Overall, our results highlight the essential yet overlooked contribution of fungi to cold seep biological networks and the role of fungi in regulating cold seep biogeochemistry. IMPORTANCE The challenges we face when analyzing eukaryotic metagenomic and metatranscriptomic data sets have hindered our understanding of cold seep fungi and microbial eukaryotes. This fact does not make the mycobiota any less critical in mediating cold seep biogeochemistry. On the contrary, many fungal genera can oxidize and solubilize methane, produce methane, and play a unique role in nutrient recycling via saprotrophic enzymatic activity. In this study, we used network analysis to uncover key fungal-prokaryotic interactions that can mediate methane biogeochemistry and metagenomics and metatranscriptomics to report that fungi are transcriptionally active in the cold seep sediment. With concerns over rising methane levels and cold seeps being a pivotal source of global methane input, our holistic understanding of methane biogeochemistry with all domains of life is essential. We ultimately encourage scientists to utilize state-of-the-art tools and multifaceted approaches to uncover the role of microeukaryotic organisms in understudied systems.

Changes in community structures and functions of the gut microbiomes of deep-sea cold seep mussels during in situ transplantation experiment.

BACKGROUND: Many deep-sea invertebrates largely depend on chemoautotrophic symbionts for energy and nutrition, and some of them have reduced functional digestive tracts. By contrast, deep-sea mussels have a complete digestive system although symbionts in their gills play vital roles in nutrient supply. This digestive system remains functional and can utilise available resources, but the roles and associations among gut microbiomes in these mussels remain unknown. Specifically, how the gut microbiome reacts to environmental change is unclear. RESULTS: The meta-pathway analysis showed the nutritional and metabolic roles of the deep-sea mussel gut microbiome. Comparative analyses of the gut microbiomes of original and transplanted mussels subjected to environmental change revealed shifts in bacterial communities. Gammaproteobacteria were enriched, whereas Bacteroidetes were slightly depleted. The functional response for the shifted communities was attributed to the acquisition of carbon sources and adjusting the utilisation of ammonia and sulphide. Self-protection was observed after transplantation. CONCLUSION: This study provides the first metagenomic insights into the community structure and function of the gut microbiome in deep-sea chemosymbiotic mussels and their critical mechanisms for adapting to changing environments and meeting of essential nutrient demand.

Genomic Insights into Niche Partitioning across Sediment Depth among Anaerobic Methane-Oxidizing Archaea in Global Methane Seeps.

Marine sediments are important methane reservoirs. Methane efflux from the seabed is significantly restricted by anaerobic methanotrophic (ANME) archaea through a process known as anaerobic oxidation of methane (AOM). Different clades of ANME archaea occupy distinct niches in methane seeps, but their underlying molecular mechanisms still need to be fully understood. To provide genetic explanations for the niche partitioning of ANME archaea, we applied comparative genomic analysis to ANME archaeal genomes retrieved from global methane seeps. Our results showed that ANME-2 archaea are more prevalent than ANME-1 archaea in shallow sediments because they carry genes that encode a significantly higher number of outer membrane multiheme c-type cytochromes and flagellar proteins. These features make ANME-2 archaea perform direct interspecies electron transfer better and benefit more from electron acceptors in AOM. Besides, ANME-2 archaea carry genes that encode extra peroxidase compared to ANME-1 archaea, which may lead to ANME-2 archaea better tolerating oxygen toxicity. In contrast, ANME-1 archaea are more competitive in deep layers than ANME-2 archaea because they carry extra genes (mtb and mtt) for methylotrophic methanogenesis and a significantly higher number of frh and mvh genes for hydrogenotrophic methanogenesis. Additionally, ANME-1 archaea carry exclusive genes (sqr, TST, and mddA) involved in sulfide detoxification compared to ANME-2 archaea, leading to stronger sulfide tolerance. Overall, this study reveals the genomic mechanisms shaping the niche partitioning among ANME archaea in global methane seeps. IMPORTANCE Anaerobic methanotrophic (ANME) archaea are important methanotrophs in marine sediment, controlling the flux of biologically generated methane, which plays an essential role in the marine carbon cycle and climate change. So far, no strain of this lineage has been isolated in pure culture, which makes metagenomics one of the fundamental approaches to reveal their metabolic potential. Although the niche partitioning of ANME archaea was frequently reported in different studies, whether this pattern was consistent in global methane seeps had yet to be verified, and little was known about the genetic mechanisms underlying it. Here, we reviewed and analyzed the community structure of ANME archaea in global methane seeps and indicated that the niche partitioning of ANME archaea was statistically supported. Our comparative genomic analysis indicated that the capabilities of interspecies electron transfer, methanogenesis, and the resistance of oxygen and hydrogen sulfide could be critical in defining the distribution of ANME archaea in methane seep sediment.

SODB facilitates comprehensive exploration of spatial omics data.

Spatial omics technologies generate wealthy but highly complex datasets. Here we present Spatial Omics DataBase (SODB), a web-based platform providing both rich data resources and a suite of interactive data analytical modules. SODB currently maintains >2,400 experiments from >25 spatial omics technologies, which are freely accessible as a unified data format compatible with various computational packages. SODB also provides multiple interactive data analytical modules, especially a unique module, Spatial Omics View (SOView). We conduct comprehensive statistical analyses and illustrate the utility of both basic and advanced analytical modules using multiple spatial omics datasets. We demonstrate SOView utility with brain spatial transcriptomics data and recover known anatomical structures. We further delineate functional tissue domains with associated marker genes that were obscured when analyzed using previous methods. We finally show how SODB may efficiently facilitate computational method development. The SODB website is https://gene.ai.tencent.com/SpatialOmics/ . The command-line package is available at https://pysodb.readthedocs.io/en/latest/ .

Mitochondrial pyruvate carrier 1 regulates fatty acid synthase lactylation and mediates treatment of nonalcoholic fatty liver disease.

BACKGROUND AND AIMS: NAFLD has become a major metabolic disease worldwide. A few studies have reported the potential relationship between mitochondrial pyruvate carrier 1 (MPC1) and inflammation, fibrosis, and insulin sensitivity in obese or NASH mouse models. However, the impact of MPC1 on NAFLD-related liver lipid metabolism and its role in the NAFLD progression require further investigation. APPROACH AND RESULTS: MPC1 expression was measured in liver tissues from normal controls and patients with NAFLD. We characterized the metabolic phenotypes and expression of genes involved in hepatic lipid accumulation in MPC1 systemic heterozygous knockout (MPC1 +/- ) mice. Hepatic protein lactylation was detected using Tandem Mass Tags proteomics and verified by the overexpression of lactylation mutants in cells. Finally, the effect of MPC1 inhibition on liver inflammation was examined in mice and AML-12 cells. Here, we found that MPC1 expression was positively correlated to liver lipid deposition in patients with NAFLD. MPC1 +/- mice fed with high-fat diet had reduced hepatic lipid accumulation but no change in the expression of lipid synthesis-related genes. MPC1 knockout affected the lactylation of several proteins, especially fatty acid synthase, through the regulation of lactate levels in hepatocytes. Lactylation at the K673 site of fatty acid synthase inhibited fatty acid synthase activity, which mediated the downregulation of liver lipid accumulation by MPC1. Moreover, although MPC1 knockout caused lactate accumulation, inflammation level was controlled because of mitochondrial protection and macrophage polarization. CONCLUSIONS: In NAFLD, MPC1 levels are positively correlated with hepatic lipid deposition; the enhanced lactylation at fatty acid synthase K673 site may be a downstream mechanism.

Interpretable artificial intelligence model for accurate identification of medical conditions using immune repertoire.

Underlying medical conditions, such as cancer, kidney disease and heart failure, are associated with a higher risk for severe COVID-19. Accurate classification of COVID-19 patients with underlying medical conditions is critical for personalized treatment decision and prognosis estimation. In this study, we propose an interpretable artificial intelligence model termed VDJMiner to mine the underlying medical conditions and predict the prognosis of COVID-19 patients according to their immune repertoires. In a cohort of more than 1400 COVID-19 patients, VDJMiner accurately identifies multiple underlying medical conditions, including cancers, chronic kidney disease, autoimmune disease, diabetes, congestive heart failure, coronary artery disease, asthma and chronic obstructive pulmonary disease, with an average area under the receiver operating characteristic curve (AUC) of 0.961. Meanwhile, in this same cohort, VDJMiner achieves an AUC of 0.922 in predicting severe COVID-19. Moreover, VDJMiner achieves an accuracy of 0.857 in predicting the response of COVID-19 patients to tocilizumab treatment on the leave-one-out test. Additionally, VDJMiner interpretively mines and scores V(D)J gene segments of the T-cell receptors that are associated with the disease. The identified associations between single-cell V(D)J gene segments and COVID-19 are highly consistent with previous studies. The source code of VDJMiner is publicly accessible at https://github.com/TencentAILabHealthcare/VDJMiner. The web server of VDJMiner is available at https://gene.ai.tencent.com/VDJMiner/.

Chitosan oligosaccharide alleviates renal fibrosis through reducing oxidative stress damage and regulating TGF-ß1/Smads pathway.

Renal fibrosis (RF) is the common pathway for a variety of chronic kidney diseases that progress to end-stage renal disease. Chitosan oligosaccharide (COS) has been identified as possessing many health functions. However, it is not clear whether COS can prevent RF. The purpose of this paper was to explore the action and mechanism of COS in alleviating RF. First, an acute unilateral ureteral obstruction operation (UUO) in male BALB/c mice was performed to induce RF, and COS or fosinopril (positive control drug) were administered for 7 consecutive days. Data from our experiments indicated that COS treatment can significantly alleviate kidney injury and decrease the levels of blood urea nitrogen (BUN) and serum creatinine (SCr) in the UUO mouse model. More importantly, our results show that COS can reduce collagen deposition and decrease the expression of fibrosis proteins, such as collagen IV, fibronectin, collagen I, α-smooth muscle actin (α-SMA) and E-cadherin, ameliorating experimental renal fibrosis in vivo. In addition, we also found that COS suppressed oxidative stress and inflammation in RF model mice. Further studies indicated that the mechanism by which COS alleviates renal fibrosis is closely related to the regulation of the TGF-ß1/Smad pathway. COS has a therapeutic effect on ameliorating renal fibrosis similar to that of the positive control drug fosinopril. Taken together, COS can alleviate renal fibrosis induced by UUO by reducing oxidative stress damage and regulating the TGF-ß1/Smad pathway.

Analytic solution for double optical metasurface beam scanners.

Optical metasurfaces are researched more and more intensively for the possible realization of lightweight and compact optical devices with novel functionalities. In this paper, a new beam-steering system based on double metasurface lenses (metalenses) is proposed and developed. The proposed system is lightweight, small volume, low cost, and easy to integrate. The exact close-form forward and numerical inverse solutions are derived respectively using the generalized Snell's law of refraction. Given the orientations of the double metalenses, the pointing position can be accurately determined. If the desired pointing position is given, the required metalenses' orientations can be obtained by applied global optimization algorithms to solve nonlinear equations related to the inverse problem. The relationships of the scan region and blind zone with the system parameters are derived. The method to eliminate the blind zone is given. Comparison with double Risley-prism systems is also conducted. This work provides a new approach to control light beams.

Disentangling the Ecological Processes Shaping the Latitudinal Pattern of Phytoplankton Communities in the Pacific Ocean.

Phytoplankton diversity and community compositions vary across spaces and are fundamentally affected by several deterministic (e.g., environmental selection) and stochastic (e.g., ecological drift) processes. How this suite of different processes regulates the biogeography of phytoplankton remains to be comprehensively explored. Using high-throughput sequencing data and null model analysis, we revealed the ecological processes shaping the latitudinal community structure of three major phytoplankton groups (i.e., diatoms, Synechococcus, and haptophytes) across the Pacific Ocean (70°N, 170°W to 35°S, 170°W). At the basin scale, heterogeneous selection (selection under heterogeneous environmental conditions) dominated the assembly processes of all phytoplankton groups; however, its relative importance varied greatly at the climatic zonal scale, explaining the distinct latitudinal α- and ß-diversity among phytoplankton groups. Assembly processes in Synechococcus and haptophyte communities were mainly controlled by physical and nutrient factors, respectively. High temperature drove Synechococcus communities to be more deterministic with higher diversity, while haptophyte communities were less environmentally selected at low latitudes due to their wide niche breadth and mixotrophic lifestyle. Diatom communities were overwhelmingly dominated by the selection process but with low correlation of measured environmental factors to their community compositions. This could be attributed to the high growth rate of diatoms, as indicated by their lower site occupation frequency than predicted in the neutral community model. Our study showed that heterogeneous selection is the main force that shaped the biogeography of three key phytoplankton groups in the Pacific Ocean, with a latitudinal variation of relative importance due to the distinct traits among phytoplankton. IMPORTANCE Phytoplankton are diverse and abundant as primary producers in the ocean, with diversity and community compositions varying spatially. How fundamental processes (e.g., selection, dispersal, and drift) regulate their global biogeography remains to be comprehensively explored. In this study, we disentangled the ecological processes of three key phytoplankton groups (i.e., diatoms, Synechococcus, and haptophytes) along the same latitudinal gradients in the Pacific Ocean. Heterogeneous selection, by promoting species richness and reducing similarity between communities, was the dominant process shaping the communities of each phytoplankton group at the basin scale. However, its relative importance varied greatly among different phytoplankton groups in different climate zones, explaining the uneven latitudinal α- and ß-diversity. We also highlight the importance of identifying key factors mediating the relative importance of assembly processes in phytoplankton communities, which will enhance our understanding of their biogeography in the ocean and future patterns under climate changes.

Dose-Response Effects of Patient Engagement on Health Outcomes in an mHealth Intervention: Secondary Analysis of a Randomized Controlled Trial.

BACKGROUND: The dose-response relationship between patient engagement and long-term intervention effects in mobile health (mHealth) interventions are understudied. Studies exploring long-term and potentially changing relationships between patient engagement and health outcomes in mHealth interventions are needed. OBJECTIVE: This study aims to examine dose-response relationships between patient engagement and 3 psychosocial outcomes in an mHealth intervention, Run4Love, using repeated measurements of outcomes at baseline and 3, 6, and 9 months. METHODS: This study is a secondary analysis using longitudinal data from the Run4Love trial, a randomized controlled trial with 300 people living with HIV and elevated depressive symptoms to examine the effects of a 3-month mHealth intervention on reducing depressive symptoms and improving quality of life (QOL). We examined the relationships between patient engagement and depressive symptoms, QOL, and perceived stress in the intervention group (N=150) using 4-time-point outcome measurements. Patient engagement was assessed using the completion rate of course assignments and frequency of items completed. Cluster analysis was used to categorize patients into high- and low-engagement groups. Generalized linear mixed effects models were conducted to investigate the dose-response relationships between patient engagement and outcomes. RESULTS: The cluster analysis identified 2 clusters that were distinctively different from each other. The first cluster comprised 72 participants with good compliance to the intervention, completing an average of 74% (53/72) of intervention items (IQR 0.22). The second cluster comprised 78 participants with low compliance to the intervention, completing an average of 15% (11/72) of intervention items (IQR 0.23). Results of the generalized linear mixed effects models showed that, compared with the low-engagement group, the high-engagement group had a significant reduction in more depressive symptoms (ß=-1.93; P=.008) and perceived stress (ß=-1.72; P<.001) and an improved QOL (ß=2.41; P=.01) over 9 months. From baseline to 3, 6, and 9 months, the differences in depressive symptoms between the 2 engagement groups were 0.8, 1.6, 2.3, and 3.7 points, respectively, indicating widening between-group differences over time. Similarly, between-group differences in QOL and perceived stress increased over time (group differences in QOL: 0.9, 1.9, 4.7, and 5.1 points, respectively; group differences in the Perceived Stress Scale: 0.9, 1.4, 2.3, and 3.0 points, respectively). CONCLUSIONS: This study revealed a positive long-term dose-response relationship between patient engagement and 3 psychosocial outcomes among people living with HIV and elevated depressive symptoms in an mHealth intervention over 9 months using 4 time-point repeat measurement data. The high- and low-engagement groups showed significant and widening differences in depressive symptoms, QOL, and perceived stress at the 3-, 6-, and 9-month follow-ups. Future mHealth interventions should improve patient engagement to achieve long-term and sustained intervention effects. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR-IPR-17012606; https://www.chictr.org.cn/showproj.aspx?proj=21019.