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Zhan, X.

Publications and source records attributed to Zhan, X..

At least 55 records · Page 3Linked to original sources

A Generalized Supervised Contrastive Learning Framework for Integrative Multi-omics Prediction Models

Recent technological advances have highlighted the significant impact of the human microbiome and metabolites on physiological conditions. Integrating microbiome and metabolite data has shown promise in predictive capabilities. We developed a new supervised contrastive learning framework, MB-SupCon-cont, that (1) proposes a general contrastive learning framework for continuous outcomes and (2) improves prediction accuracy over models using single omics data. Simulation studies confirmed the improved performance of MB-SupCon-cont, and applied scenarios in type 2 diabetes and high-fat diet studies also showed improved prediction performance. Overall, MB-SupCon-cont is a versatile research tool for multi-omics prediction models.

bioinformatics↗

ScopeViewer: A Browser-Based Solution for Visualizing Spatial Transcriptomics Data

MotivationSpatial transcriptomics (ST) enables a high-resolution interrogation of molecular characteristics within specific spatial contexts and tissue morphology. Despite its potential, visualization of ST data is a challenging task due to the complexities in handling, sharing and visualizing large image datasets together with molecular information. ResultsWe introduce ScopeViewer, a browser-based software designed to overcome these challenges. ScopeViewer offers the following functionalities: (1) It visualizes large image data and associated annotations at various zoom levels, allowing for intricate exploration of the data; (2) It enables dual interactive viewing of the original images along with their annotations, providing a comprehensive understanding of the context; (3) It displays spatial molecular features with optimized bandwidth, ensuring a smooth user experience; and (4) It bolsters data security by circumventing data transfers. AvailabilityScopeViewer is available at: https://datacommons.swmed.edu/scopeviewer ContactXiaowei.Zhan@UTSouthwestern.edu, Guanghua.Xiao@UTSouthwestern.edu Supplementary informationSupplementary data are available at Bioinformatics online.

bioinformatics↗

Genetic Determinants Underlying the Progressive Phenotype of Beta-lactam/Beta-lactamase Inhibitor Resistance in Escherichia coli

Currently, whole genome sequencing (WGS) data has not shown strong concordance with E. coli susceptibility profiles to the commonly used {beta}-lactam/{beta}-lactamase inhibitor (BL/BLI) combinations: ampicillin-sulbactam (SAM), amoxicillin-clavulanate (AMC), and piperacillin-tazobactam (TZP). Progressive resistance to these BL/BLIs in absence of cephalosporin resistance, also known as extended-spectrum resistance to BL/BLI (ESRI), has been suggested to primarily result from increased copy numbers of blaTEM variants, which is not routinely assessed in WGS data. We sought to determine whether addition of gene amplification could improve genotype-phenotype associations through WGS analysis of 147 E. coli bacteremia isolates with increasing categories of BL/BLI non-susceptibility ranging from ampicillin-susceptible to fully resistant to all three BL/BLIs. Consistent with a key role of blaTEM in ESRI, 112/134 strains (84%) with at least ampicillin non-susceptibility encoded blaTEM. Evidence of blaTEM amplification (i.e., blaTEM gene copy number estimates > 2x) was present in 40/112 (36%) strains. There were positive correlations between blaTEM copy numbers with minimum inhibitory concentrations (MICs) of AMC and TZP (P-value < 0.05), but not for SAM (P-value = 0.09). The diversity of {beta}-lactam resistance mechanisms, including non-ceftriaxone hydrolyzing blaCTX-M variants, blaOXA-1, as well as ampC and blaTEM strong promoter mutations, were greater in AMC and TZP non-susceptible strains but rarely observed within SAM and AMP non-susceptible isolates. Our study indicates a comprehensive analysis of WGS data, including {beta}-lactamase encoding gene amplification, can help categorize E. coli with AMC or TZP non-susceptibility but that discerning the transition from SAM susceptible to non-susceptible using genetic data requires further refinement. ImportanceThe increased feasibility of whole genome sequencing has generated significant interest in using such molecular diagnostic approaches to characterize difficult-to-treat, antimicrobial resistant (AMR) infections. Nevertheless, there are current limitations in the accurate prediction of AMR phenotypes based on existing AMR gene database approaches, which primarily correlate a phenotype with the presence/absence of a single AMR gene. Our study utilized a large cohort of cephalosporin-susceptible E. coli bacteremia samples to determine how increasing dosage of narrow-spectrum {beta}-lactamase encoding genes in conjunction with other diverse BL/BLI genetic determinants contribute to progressively more severe BL/BLI phenotypes. We were able to characterize the complexity of the genetic mechanisms underlying progressive BL/BLI resistance including the critical role of {beta}-lactamase encoding gene amplification. For the diverse array of AMR phenotypes with complex mechanisms involving multiple genomic factors, our study provides an example of how composite risk scores may improve understanding of AMR genotype/phenotype correlations.

genomics↗

Spatial Transcriptomics Arena (STAr): an Integrated Platform for Spatial Transcriptomics Methodology Research

The emerging field of spatially resolved transcriptomics (SRT) has revolutionized biomedical research. SRT quantifies expression levels at different spatial locations, providing a new and powerful tool to interrogate novel biological insights. An essential question in the analysis of SRT data is to identify spatially variable (SV) genes; the expression levels of such genes have spatial variation across different tissues. SV genes usually play an important role in underlying biological mechanisms and tissue heterogeneity. Currently, several computational methods have been developed to detect such genes; however, there is a lack of unbiased assessment of these approaches to guide researchers in selecting the appropriate methods for their specific biomedical applications. In addition, it is difficult for researchers to implement different existing methods for either biological study or methodology development. Furthermore, currently available public SRT datasets are scattered across different websites and preprocessed in different ways, posing additional obstacles for quantitative researchers developing computational methods for SRT data analysis. To address these challenges, we designed Spatial Transcriptomics Arena (STAr), an open platform comprising 193 curated datasets from seven technologies, seven statistical methods, and analysis results. This resource allows users to retrieve high-quality datasets, apply or develop spatial gene detection methods, as well as browse and compare spatial gene analysis results. It also enables researchers to comprehensively evaluate SRT methodology research in both simulated and real datasets. Altogether, STAr is an integrated research resource intended to promote reproducible research and accelerate rigorous methodology development, which can eventually lead to an improved understanding of biological processes and diseases. STAr can be accessed at https://lce.biohpc.swmed.edu/star/.

genomics↗

Susceptible bacteria survive antibiotic treatment in the mammalian gastrointestinal tract without evolving resistance

In vitro systems have provided great insight into the mechanisms of antibiotic resistance. Yet, in vitro approaches cannot reflect the full complexity of what transpires within a host. As the mammalian gut is host to trillions of resident bacteria and thus a potential breeding ground for antibiotic resistance, we sought to better understand how gut bacteria respond to antibiotic treatment in vivo. Here, we colonized germ-free mice with a genetically barcoded antibiotic pan-susceptible Escherichia coli clinical isolate and then administered the antibiotic cefepime via programmable subcutaneous pumps which allowed for closer emulation of human parenteral antibiotic pharmacokinetics/dynamics. After seven days of antibiotics, we were unable to culture E. coli from feces. We were, however, able to recover barcoded E. coli from harvested gastrointestinal (GI) tissue, despite high GI tract and plasma cefepime concentrations. Strikingly, these E. coli isolates were not resistant to cefepime but had acquired mutations - most notably in the wbaP gene, which encodes an enzyme required for the initiation of the synthesis of the polysaccharide capsule and lipopolysaccharide O antigen - that increased their ability to invade and survive within intestinal cells, including cultured human colonocytes. Further, these E. coli mutants exhibited a persister phenotype when exposed to cefepime, allowing for greater survival to pulses of cefepime treatment when compared to the wildtype strain. Our findings highlight a mechanism by which bacteria in the gastrointestinal tract can adapt to antibiotic treatment by increasing their ability to persist during antibiotic treatment and invade intestinal epithelial cells where antibiotic concentrations are substantially reduced.

microbiology↗

IsoAnalytics: A Single-cell Proteomics Web Server

MotivationSingle-cell proteomics provide unprecedented resolution to examine biological processes. Customized data analysis and facile data visualization are crucial for scientific discovery. Further, userfriendly data analysis and visualization software that is easily accessible for the general scientific community is essential. ResultsWe have created a web server, IsoAnalytics, that gives users without computational or bioinformatics background the ability to directly analyze and interactively visualize data obtained from the Isoplexis single cell technology platform. We envision this open-sourced web server will increase research productivity and serve as a free, competitive alternative for single-cell proteomics research. ContactAndrew.Koh@utsouthwestern.edu and Xiaowei.Zhan@utsouthwestern.edu AvailabilityIsoAnalytics is free and available at: https://cdc.biohpc.swmed.edu/isoplexis/ and is implemented in Python, with all major browsers supported. Code for IsoAnalytics is free and available at: https://github.com/zhanxw/Isoplexis_Data_Analysis. Supplementary InformationSupplementary data are available at Bioinformatics online.

bioinformatics↗

A Deep Learning Approach for Histology-Based Nuclei Segmentation and Tumor Microenvironment Characterization

Microscopic examination of pathology slides is essential to disease diagnosis and biomedical research; however, traditional manual examination of tissue slides is laborious and subjective. Tumor whole-slide image (WSI) scanning is becoming part of routine clinical procedure and produces massive data that capture tumor histological details at high resolution. Furthermore, the rapid development of deep learning algorithms has significantly increased the efficiency and accuracy of pathology image analysis. In light of this progress, digital pathology is fast becoming a powerful tool to assist pathologists. Studying tumor tissue and its surrounding microenvironment provides critical insight into tumor initiation, progression, metastasis, and potential therapeutic targets. Nuclei segmentation and classification are critical to pathology image analysis, especially in characterizing and quantifying the tumor microenvironment (TME). Computational algorithms have been developed for nuclei segmentation and TME quantification within image patches; however, existing algorithms are computationally intensive and time-consuming for WSI analysis. In this study, we present Histology-based Detection using Yolo (HD-Yolo), a new method that significantly accelerates nuclei segmentation and TME quantification. We demonstrate that HD-Yolo outperforms existing methods for WSI analysis in nuclei detection and classification accuracy, as well as computation time.

pathology↗

Structural Insights into Branch Site Proofreading by Human Spliceosome

Selection of the pre-mRNA branch site (BS) by U2 snRNP is crucial to prespliceosome (A complex) assembly. The RNA helicase PRP5 proofreads BS selection; but the underlying mechanism remains unclear. Here we report the atomic structures of two sequential complexes leading to prespliceosome assembly: human 17S U2 snRNP and a cross-exon pre-A complex. PRP5 is anchored on 17S U2 snRNP mainly through occupation of the RNA path of SF3B1 by an acidic loop of PRP5; the helicase domain of PRP5 associates with U2 snRNA; the BS-interacting stem loop (BSL) of U2 snRNA is shielded by the splicing factor TAT-SF1, unable to engage the BS. In the pre-A complex, an initial U2/BS duplex is formed; the translocated helicase domain of PRP5 stays with U2 snRNA; the acidic loop still occupies the RNA path. The pre-A conformation is specifically stabilized by the splicing factors SF1, DNAJC8 and SF3A2. Cancer-derived mutations in SF3B1 damage its association with PRP5, compromising BS proofreading. Together, these findings reveal key insights into prespliceosome assembly and BS selection/proofreading by PRP5.

biochemistry↗

Mapping global land sharing-sparing patterns between human and wildlife

Understanding the global patterns of land sharing-sparing between humans and wildlife is essential for pragmatic conservation implementation, yet analytical foundations and indicator-based assessments are still lacking. By integrating distributions of 30,664 terrestrial vertebrates and human pressures, we provide a series of spatial explicit Human-Nature Indices (HNIs) before classifying the global lands into four categories. We found that the Co-occurring (C) regions, where lands are shared by humans and wildlife, are not insignificant (16.91% of global land). For land-sparing, the Diversity-intact (D) and the Anthropic (A) regions account for 45.64% and 1.41% of the land, respectively. The patterns of HNIs, varying considerably among taxonomic groups, are determined mainly by the expansion of human-dominated land use. Land sharing and sparing could work as complementary strategies to support biodiversity and human development toward ambitious and pragmatic 30 by 30 goals. Our results highlight that those regions should adopt different conservation strategies according to their sharing-sparing patterns and distribution of protected areas.

ecology↗

MB-SupCon: Microbiome-based predictive models via Supervised Contrastive Learning

Human microbiome consists of trillions of microorganisms. Microbiota can modulate the host physiology through molecule and metabolite interactions. Integrating microbiome and metabolomics data have the potential to predict different diseases more accurately. Yet, most datasets only measure microbiome data but without paired metabolome data. Here, we propose a novel integrative modeling framework, Microbiome-based Supervised Contrastive Learning Framework (MB-SupCon). MB-SupCon integrates microbiome and metabolome data to generate microbiome embeddings, which can be used to improve the prediction accuracy in datasets that only measure microbiome data. As a proof of concept, we applied MB-SupCon on 720 samples with paired 16S microbiome data and metabolomics data from patients with type 2 diabetes. MB-SupCon outperformed existing prediction methods and achieves high average prediction accuracies for insulin resistance status (84.62%), sex (78.98%), and race (80.04%). Moreover, the microbiome embeddings form separable clusters for different covariate groups in the lower-dimensional space, which enhances data visualization. We also applied MB-SupCon on a large inflammatory bowel disease study and observed similar advantages. Thus, MB-SupCon could be broadly applicable to improve microbiome prediction models in multi-omics disease studies.

bioinformatics↗

Systematic Analysis of Mobile Genetic Elements Mediating β-lactamase Gene Amplification in Non-Carbapenemase-Producing Carbapenem Resistant Enterobacterales Bloodstream Infections

Non-carbapenemase-producing carbapenem resistant Enterobacterales (non-CP-CRE) are increasingly recognized as important contributors to prevalent carbapenem resistant Enterobacterales (CRE) infections. However, there is limited understanding of mechanisms underlying non-CP-CRE causing invasive disease. Long- and short-read whole genome sequencing (WGS) was used to elucidate carbapenem non-susceptibility determinants in Enterobacterales bloodstream isolates at MD Anderson Cancer Center in Houston, Texas. We investigated carbapenem non-susceptible Enterobacterales (CNSE) mechanisms through a combination of phylogenetic analysis, antimicrobial resistant (AMR) gene detection/copy number quantification, porin assessment, and mobile genetic element (MGE) characterization. Most CNSE isolates sequenced were non-CP-CRE (41/79; 51.9%) whereas 25.3% (20/79) were carbapenem intermediate Enterobacterales (CIE) and 22.8% (18/79) were carbapenemase producing Enterobacterales (CPE). Statistically significant copy number variants (CNVs) of extended-spectrum {beta}-lactamase (ESBL) genes (Wilcoxon Test; p-value < 0.001) were present in both non-CP-CR E. coli (median CNV = 2.6X; n= 17) and K. pneumoniae (median CNV = 3.2X, n = 17). All non-CP-CR E. coli and K. pneumoniae had predicted reduced expression of at least one outer membrane porin gene (i.e., ompC/ompF or ompK36/ompK35). Completely resolved CNSE genomes revealed that IS26 and ISEcp1 structures harboring blaCTX-M variants along with other AMR elements were the primary drivers of gene amplification, occurring in mostly IncFIB/IncFII plasmid contexts. MGE mediated {beta}-lactamase gene amplifications resulted in either tandem arrays, primarily mediated by IS26 translocatable units, or segmental duplication, typically due to ISEcp1 transposition units. Non-CP-CRE strains were the most prevalent cause of CRE bacteremia with carbapenem non-susceptibility driven by concurrent porin loss and MGE-mediated amplification of blaCTX-M genes. IMPORTANCECarbapenem resistant Enterobacterales (CRE) are considered urgent antimicrobial resistance (AMR) threats. The vast majority of CRE research has focused on carbapenemase producing Enterobacterales (CPE) even though non-carbapenemase-producing CRE (non-CP-CRE) comprise 50% or more of isolates in some surveillance studies. Thus, carbapenem resistance mechanisms in non-CP-CRE remain poorly characterized. To address this problem, we applied a combination of short- and long-read sequencing technologies to a cohort of CRE bacteremia isolates and used these data to unravel complex mobile genetic element structures mediating {beta}- lactamase gene amplification. By generating complete genomes of 65 carbapenem non-susceptible Enterobacterales (CNSE) covering a genetically diverse array of isolates, our findings both generate novel insights into how non-CP-CRE overcome carbapenem treatments and provide researchers scaffolds for characterization of their own non-CP-CRE isolates. Improved recognition of mechanisms driving development of non-CP-CRE could assist with design and implementation of future strategies to mitigate the impact of these increasingly recognized AMR pathogens.

genomics↗

Near-atomic Structure of the Cytoplasmic Ring of the Xenopus laevis Nuclear Pore Complex

The nuclear pore complex (NPC) mediates nucleocytoplasmic shuttling. Here we present single-particle cryo-EM structure of the cytoplasmic ring (CR) from the Xenopus laevis NPC at 4.1-4.7 [A] resolutions. The structure of an N-terminal domain of Nup358 was resolved at 3.0 [A], facilitating identification of five Nup358 molecules in each CR subunit. Aside from unveiling the assembly details of the two Y-shaped multicomponent complexes (Y complexes) in each CR subunit, the improved resolutions reveal the C-terminal fragment of Nup160 to be an organizing center at the vertex of each Y complex. Our structures show that the scaffold of a CR subunit comprises five Nup358, two Nup205 and two Nup93 molecules in addition to the previously characterized Y complexes. One-Sentence SummaryImproved resolutions of the cytoplasmic ring (CR) of the Xenopus laevis nuclear pore complex reveal that five Nup358 molecules, together with two copies of interweaved Nup205, Nup93 and Y complexes, constitute the scaffold of each CR subunit.

biophysics↗

Immune checkpoint blockade induces gut microbiota translocation that augments extraintestinal anti-tumor immunity

Gut microbiota are critical for effective immune checkpoint blockade therapy (ICT) for cancer. The mechanisms by which gut microbiota augment extraintestinal anti-cancer immune responses, however, are largely unknown. Here, we find that ICT induces translocation of specific endogenous gut microbiota into secondary lymphoid organs and subcutaneous melanoma tumors. Mechanistically, gut microbiota activated dendritic cells (DCs) traffic a selective subset of gut bacteria to mesenteric lymph nodes (MLN) and promote optimal anti-tumor T-cell responses in both the tumor draining lymph nodes (TDLN) and the primary tumor. Antibiotic treatment resulted in decreased gut microbiota translocation into MLN and TDLN, diminished polyfunctional effector CD8+ T cell responses, and attenuated response to ICT. Our findings illuminate a key mechanism by which gut microbiota promote extraintestinal anti-cancer immunity. One sentence summaryFollowing immune checkpoint blockade therapy, dendritic cells traffic gut microbiota into secondary lymphoid organs, promoting optimal extraintestinal anti-cancer immunity.

immunology↗

Neutralization Fingerprinting Technology for Characterizing Polyclonal Antibody Responses to Dengue Vaccines

Dengue is a major public health threat. There are four serotypes of dengue virus (DENV), therefore efforts are focused on development of safe and effective tetravalent DENV vaccines. While neutralizing antibodies contribute to protective immunity, there are still important gaps in understanding of immune responses elicited by dengue infection and vaccination, including defining immune correlates of protection. To that end, here we present a computational modeling framework for evaluating the specificities of neutralizing antibodies elicited to tetravalent DENV vaccines, based on the concept of antibody-virus neutralization fingerprints. We developed and applied this framework to samples from clinical studies of TAK-003, a tetravalent vaccine candidate currently in phase 3 trials, to characterize the effect of prior dengue infection (baseline) on the specificities of vaccine-elicited antibody responses. Our results suggested a similarity of neutralizing antibody specificities in baseline-seronegative individuals. In contrast, amplification of pre-existing neutralizing antibody specificities was predicted for baseline-seropositive individuals, thus quantifying the role of immunologic imprinting in driving antibody responses to DENV vaccines. The analysis framework proposed here can apply to studies of sequential dengue infections and other tetravalent DENV vaccines and can contribute to understanding dengue immune correlates of protection to help guide further vaccine development and optimization.

immunology↗

A Novel Oncogenic Function of PRC2 Heterogeneity in Medulloblastoma

Intratumor epigenetic heterogeneity is emerging as a key mechanism underlying tumor evolution and drug resistance. Medulloblastomas, the most common childhood malignant brain tumor, are classified into four subtypes including SHH medulloblastomas, which are characterized by elevated SHH signaling and a cerebellum granule neuron precursor (CGNP) cell-of-origin. Medulloblastomas are highly associated with epigenetic abnormalities. We observed that the histone H3K27 methyltransferase polycomb repressor complex 2 (PRC2) is often heterogeneous within individual SHH medulloblastoma tumors. Using mouse models, we showed that while a complete deletion of the PRC2 core subunit EED inhibited medulloblastoma growth, a mosaic deletion of EED significantly enhanced tumor growth. EED is intrinsically required for CGNP maintenance by inhibiting both neural differentiation and cell death. Complete EED deletion led to CGNP depletion and reduced occurrence of medulloblastoma. Surprisingly, we found that medulloblastomas with mosaic EED levels grew faster than did control wildtype tumors and expressed increased levels of oncogenes such as Igf2. Igf2 is directly repressed by PRC2 and has been demonstrated to be both necessary and sufficient for SHH medulloblastoma progression. We showed that IGF2 mediated the oncogenic effects of PRC2 heterogeneity in tumor growth. Using a human medulloblastoma cell line, we generated clones with different EED levels and confirmed that EEDlow cells could stimulate the growth of EEDhigh cells through derepressed IGF2 signals. Thus, PRC2 heterogeneity controls medulloblastoma growth through both intrinsic growth competence and non-cell autonomous mechanisms in distinct tumor subclones. We reveal a novel oncogenic function of PRC2 heterogeneity in tumor development.

cancer biology↗

Cryo-EM structure of the Inner Ring from Xenopus laevis Nuclear Pore Complex

Nuclear pore complex (NPC) mediates nucleocytoplasmic shuttling. Here we present single-particle cryo-electron microscopy (cryo-EM) structure of the inner ring (IR) subunit from Xenopus laevis NPC at an average resolution of 4.4 [A]. The symmetric IR subunit comprises a cytoplasmic half and a nuclear half. A homo-dimer of Nup205 resides at the center of the IR subunit, flanked by two molecules of Nup188. Four molecules of Nup93 each places an extended helix into the axial groove of Nup205 or Nup188, together constituting the central scaffold. The channel nucleoporin heterotrimer (CNT) of Nup54/58/62 is anchored on the central scaffold. Six Nup155 molecules interact with the central scaffold and together with the NDC1-ALADIN hetero-dimers anchor the IR subunit to the nuclear envelope and to outer rings. The scarce inter-subunit contacts may allow sufficient latitude in conformation and diameter of the IR. Our structure of vertebrate IR reveals key insights that are functionally important.

biophysics↗

Transcriptome innovations in primates revealed by single-molecule long-read sequencing

Transcriptomic diversity greatly contributes to the fundamentals of disease, lineage-specific biology, and environmental adaptation. However, much of the actual isoform repertoire contributing to shaping primate evolution remains unknown. Here, we combined deep long- and short-read sequencing complemented with mass spectrometry proteomics in a panel of lymphoblastoid cell lines (LCLs) from human, three other great apes, and rhesus macaque, producing the largest full-length isoform catalog in primates to date. Our transcriptomes reveal thousands of novel transcripts, some of them under active translation, expanding and completing the repertoire of primate gene models. Our comparative analyses unveil hundreds of transcriptomic innovations and isoform usage changes related to immune function and immunological disorders. The confluence of these innovations with signals of positive selection and their limited impact in the proteome points to changes in alternative splicing in genes involved in immune response as an important target of recent regulatory divergence in primates.

evolutionary biology↗

Kernel-based genetic association analysis for microbiome phenotypes identifies host genetic drivers of beta-diversity

Understanding human genetic influences on the gut microbiota helps elucidate the mechanisms by which genetics affects health outcomes. We propose a novel approach, the covariate-adjusted kernel RV (KRV) framework, to map genetic variants associated with microbiome beta-diversity, which focuses on overall shifts in the microbiota. The proposed KRV framework improves statistical power by capturing intrinsic structure within the genetic and microbiome data while reducing the multiple-testing burden. We apply the covariate-adjusted KRV test to the Hispanic Community Health Study/Study of Latinos in a genome-wide association analysis (first gene-level, then variant-level) for microbiome beta-diversity. We have identified an immunity-related gene, IL23R, reported in previous association studies and discovered 3 other novel genes, 2 of which are involved in immune functions or autoimmune disorders. Our findings highlight the value of the KRV as a powerful microbiome GWAS approach and support an important role of immunity-related genes in shaping the gut microbiome composition.

genomics↗