HIV-associated gut microbial alterations are dependent on host and geographic context.

HIV-associated changes in intestinal microbiota are believed to be important drivers of disease progression. However, the majority of studies have focused on populations in high-income countries rather than in developing regions where HIV burden is greatest. To better understand the impact of HIV on fecal microbiota globally, we compare the fecal microbial community of individuals in the U.S., Uganda, and Botswana. We identify significant bacterial taxa alterations with both treated and untreated HIV infection with a high degree of uniqueness in each cohort. HIV-associated taxa alterations are also significantly different between populations that report men who have sex with men (MSM) behavior and non-MSM populations. Additionally, while we find that HIV infection is consistently associated with higher soluble markers of immune activation, most specific bacterial taxa associated with these markers in each region are not shared and none are shared across all three geographic locations in our study. Our findings demonstrate that HIV-associated changes in fecal microbiota are overall distinct among geographical locations and sexual behavior groups, although a small number of taxa shared between pairs of geographic locations warrant further investigation, highlighting the importance of considering host context to fully assess the impact of the gut microbiome on human health and disease.

Tobacco smoke exposure recruits inflammatory airspace monocytes that establish permissive lung niches for Mycobacterium tuberculosis.

Tobacco smoking doubles the risk of active tuberculosis (TB) and accounts for up to 20% of all active TB cases globally. How smoking promotes lung microenvironments permissive to Mycobacterium tuberculosis (Mtb) growth remains incompletely understood. We investigated primary bronchoalveolar lavage cells from current and never smokers by performing single-cell RNA sequencing (scRNA-seq), flow cytometry, and functional assays. We observed the enrichment of immature inflammatory monocytes in the lungs of smokers compared with nonsmokers. These monocytes exhibited phenotypes consistent with recent recruitment from blood, ongoing differentiation, increased activation, and states similar to those with chronic obstructive pulmonary disease. Using integrative scRNA-seq and flow cytometry, we identified CD93 as a marker for a subset of these newly recruited smoking-associated lung monocytes and further provided evidence that the recruitment of monocytes into the lung was mediated by CCR2-binding chemokines, including CCL11. We also show that these cells exhibit elevated inflammatory responses upon exposure to Mtb and accelerated intracellular growth of Mtb compared with mature macrophages. This elevated Mtb growth could be inhibited by anti-inflammatory small molecules, providing a connection between smoking-induced pro-inflammatory states and permissiveness to Mtb growth. Our findings suggest a model in which smoking leads to the recruitment of immature inflammatory monocytes from the periphery to the lung, which results in the accumulation of these Mtb-permissive cells in the airway. This work defines how smoking may lead to increased susceptibility to Mtb and identifies host-directed therapies to reduce the burden of TB among those who smoke.

Sub-communities of the vaginal microbiota in pregnant and non-pregnant women.

Diverse and non-Lactobacillus-dominated vaginal microbial communities are associated with adverse health outcomes such as preterm birth and the acquisition of sexually transmitted infections. Despite the importance of recognizing and understanding the key risk-associated features of these communities, their heterogeneous structure and properties remain ill-defined. Clustering approaches are commonly used to characterize vaginal communities, but they lack sensitivity and robustness in resolving substructures and revealing transitions between potential sub-communities. Here, we address this need with an approach based on mixed membership topic models. Using longitudinal data from cohorts of pregnant and non-pregnant study participants, we show that topic models more accurately describe sample composition, longitudinal changes, and better predict the loss of Lactobacillus dominance. We identify several non-Lactobacillus-dominated sub-communities common to both cohorts and independent of reproductive status. In non-pregnant individuals, we find that the menstrual cycle modulates transitions between and within sub-communities, as well as the concentrations of half of the cytokines and 18% of metabolites. Overall, our analyses based on mixed membership models reveal substructures of vaginal ecosystems which may have important clinical and biological associations.

Abrupt perturbation and delayed recovery of the vaginal ecosystem following childbirth.

The vaginal ecosystem is closely tied to human health and reproductive outcomes, yet its dynamics in the wake of childbirth remain poorly characterized. Here, we profile the vaginal microbiota and cytokine milieu of participants sampled longitudinally throughout pregnancy and for at least one year postpartum. We show that delivery, regardless of mode, is associated with a vaginal pro-inflammatory cytokine response and the loss of Lactobacillus dominance. By contrast, neither the progression of gestation nor the approach of labor strongly altered the vaginal ecosystem. At 9.5-months postpartum-the latest timepoint at which cytokines were assessed-elevated inflammation coincided with vaginal bacterial communities that had remained perturbed (highly diverse) from the time of delivery. Time-to-event analysis indicated a one-year postpartum probability of transitioning to Lactobacillus dominance of 49.4%. As diversity and inflammation declined during the postpartum period, dominance by L. crispatus, the quintessential health-associated commensal, failed to return: its prevalence before, immediately after, and one year after delivery was 41%, 4%, and 9%, respectively. Revisiting our pre-delivery data, we found that a prior live birth was associated with a lower odds of L. crispatus dominance in pregnant participants-an outcome modestly tempered by a longer ( > 18-month) interpregnancy interval. Our results suggest that reproductive history and childbirth in particular remodel the vaginal ecosystem and that the timing and degree of recovery from delivery may help determine the subsequent health of the woman and of future pregnancies.

Metagenomic assessment of gut microbial communities and risk of severe COVID-19.

BACKGROUND: The gut microbiome is a critical modulator of host immunity and is linked to the immune response to respiratory viral infections. However, few studies have gone beyond describing broad compositional alterations in severe COVID-19, defined as acute respiratory or other organ failure. METHODS: We profiled 127 hospitalized patients with COVID-19 (n = 79 with severe COVID-19 and 48 with moderate) who collectively provided 241 stool samples from April 2020 to May 2021 to identify links between COVID-19 severity and gut microbial taxa, their biochemical pathways, and stool metabolites. RESULTS: Forty-eight species were associated with severe disease after accounting for antibiotic use, age, sex, and various comorbidities. These included significant in-hospital depletions of Fusicatenibacter saccharivorans and Roseburia hominis, each previously linked to post-acute COVID syndrome or "long COVID," suggesting these microbes may serve as early biomarkers for the eventual development of long COVID. A random forest classifier achieved excellent performance when tasked with classifying whether stool was obtained from patients with severe vs. moderate COVID-19, a finding that was externally validated in an independent cohort. Dedicated network analyses demonstrated fragile microbial ecology in severe disease, characterized by fracturing of clusters and reduced negative selection. We also observed shifts in predicted stool metabolite pools, implicating perturbed bile acid metabolism in severe disease. CONCLUSIONS: Here, we show that the gut microbiome differentiates individuals with a more severe disease course after infection with COVID-19 and offer several tractable and biologically plausible mechanisms through which gut microbial communities may influence COVID-19 disease course. Further studies are needed to expand upon these observations to better leverage the gut microbiome as a potential biomarker for disease severity and as a target for therapeutic intervention.

Distinct cervical tissue-adherent and luminal microbiome communities correlate with mucosal host gene expression and protein levels in Kenyan sex workers.

BACKGROUND: The majority of studies characterizing female genital tract microbiota have focused on luminal organisms, while the presence and impact of tissue-adherent ectocervical microbiota remain incompletely understood. Studies of luminal and tissue-associated bacteria in the gastrointestinal tract suggest that these communities may have distinct roles in health and disease. Here, we performed a multi-omics characterization of paired luminal and tissue samples collected from a cohort of Kenyan female sex workers. RESULTS: We identified a tissue-adherent bacterial microbiome, with a higher alpha diversity than the luminal microbiome, in which dominant genera overall included Gardnerella and Lactobacillus, followed by Prevotella, Atopobium, and Sneathia. About half of the L. iners-dominated luminal samples had a corresponding Gardnerella-dominated tissue microbiome. Broadly, the tissue-adherent microbiome was associated with fewer differentially expressed host genes than the luminal microbiome. Gene set enrichment analysis revealed that L. crispatus-dominated tissue-adherent communities were associated with protein translation and antimicrobial activity, whereas a highly diverse microbial community was associated with epithelial remodeling and pro-inflammatory pathways. Tissue-adherent communities dominated by L. iners and Gardnerella were associated with lower host transcriptional activity. Tissue-adherent microbiomes dominated by Lactobacillus and Gardnerella correlated with host protein profiles associated with epithelial barrier stability, although with a more pro-inflammatory profile for the Gardnerella-dominated microbiome group. Tissue samples with a highly diverse composition had a protein profile representing cell proliferation and pro-inflammatory activity. CONCLUSION: We identified ectocervical tissue-adherent bacterial communities in all study participants of a female sex worker cohort. These communities were distinct from cervicovaginal luminal microbiota in a significant proportion of individuals. We further revealed that bacterial communities at both sites correlated with distinct host gene expression and protein levels. The tissue-adherent bacterial community could possibly act as a reservoir that seed the lumen with less optimal, non-Lactobacillus, bacteria. Video Abstract.

Low protease activity in B cell follicles promotes retention of intact antigens after immunization.

The structural integrity of vaccine antigens is critical to the generation of protective antibody responses, but the impact of protease activity on vaccination in vivo is poorly understood. We characterized protease activity in lymph nodes and found that antigens were rapidly degraded in the subcapsular sinus, paracortex, and interfollicular regions, whereas low protease activity and antigen degradation rates were detected in the vicinity of follicular dendritic cells (FDCs). Correlated with these findings, immunization regimens designed to target antigen to FDCs led to germinal centers dominantly targeting intact antigen, whereas traditional immunizations led to much weaker responses that equally targeted the intact immunogen and antigen breakdown products. Thus, spatially compartmentalized antigen proteolysis affects humoral immunity and can be exploited.

Vaginal Lactobacillus fatty acid response mechanisms reveal a novel strategy for bacterial vaginosis treatment.

Bacterial vaginosis (BV), a common syndrome characterized by Lactobacillus-deficient vaginal microbiota, is associated with adverse health outcomes. BV often recurs after standard antibiotic therapy in part because antibiotics promote microbiota dominance by Lactobacillus iners instead of Lactobacillus crispatus, which has more beneficial health associations. Strategies to promote L. crispatus and inhibit L. iners are thus needed. We show that oleic acid (OA) and similar long-chain fatty acids simultaneously inhibit L. iners and enhance L. crispatus growth. These phenotypes require OA-inducible genes conserved in L. crispatus and related species, including an oleate hydratase (ohyA) and putative fatty acid efflux pump (farE). FarE mediates OA resistance, while OhyA is robustly active in the human vaginal microbiota and sequesters OA in a derivative form that only ohyA-harboring organisms can exploit. Finally, OA promotes L. crispatus dominance more effectively than antibiotics in an in vitro model of BV, suggesting a novel approach for treatment.

Vaginal microbiome-host interactions modeled in a human vagina-on-a-chip.

BACKGROUND: A dominance of non-iners Lactobacillus species in the vaginal microbiome is optimal and strongly associated with gynecological and obstetric health, while the presence of diverse obligate or facultative anaerobic bacteria and a paucity in Lactobacillus species, similar to communities found in bacterial vaginosis (BV), is considered non-optimal and associated with adverse health outcomes. Various therapeutic strategies are being explored to modulate the composition of the vaginal microbiome; however, there is no human model that faithfully reproduces the vaginal epithelial microenvironment for preclinical validation of potential therapeutics or testing hypotheses about vaginal epithelium-microbiome interactions. RESULTS: Here, we describe an organ-on-a-chip (organ chip) microfluidic culture model of the human vaginal mucosa (vagina chip) that is lined by hormone-sensitive, primary vaginal epithelium interfaced with underlying stromal fibroblasts, which sustains a low physiological oxygen concentration in the epithelial lumen. We show that the Vagina Chip can be used to assess colonization by optimal L. crispatus consortia as well as non-optimal Gardnerella vaginalis-containing consortia, and to measure associated host innate immune responses. Co-culture and growth of the L. crispatus consortia on-chip was accompanied by maintenance of epithelial cell viability, accumulation of D- and L-lactic acid, maintenance of a physiologically relevant low pH, and down regulation of proinflammatory cytokines. In contrast, co-culture of G. vaginalis-containing consortia in the vagina chip resulted in epithelial cell injury, a rise in pH, and upregulation of proinflammatory cytokines. CONCLUSION: This study demonstrates the potential of applying human organ chip technology to create a preclinical model of the human vaginal mucosa that can be used to better understand interactions between the vaginal microbiome and host tissues, as well as to evaluate the safety and efficacy of live biotherapeutics products. Video Abstract.

Screening and characterization of vaginal fluid donations for vaginal microbiota transplantation.

Bacterial vaginosis (BV), the overgrowth of diverse anaerobic bacteria in the vagina, is the most common cause of vaginal symptoms worldwide. BV frequently recurs after antibiotic therapy, and the best probiotic treatments only result in transient changes from BV-associated states to "optimal" communities dominated by a single species of Lactobacillus. Therefore, additional treatment strategies are needed to durably alter vaginal microbiota composition for patients with BV. Vaginal microbiota transplantation (VMT), the transfer of vaginal fluid from a healthy person with an optimal vaginal microbiota to a recipient with BV, has been proposed as one such alternative. However, VMT carries potential risks, necessitating strict safety precautions. Here, we present an FDA-approved donor screening protocol and detailed methodology for donation collection, storage, screening, and analysis of VMT material. We find that Lactobacillus viability is maintained for over six months in donated material stored at - 80 °C without glycerol or other cryoprotectants. We further show that species-specific quantitative PCR for L. crispatus and L. iners can be used as a rapid initial screening strategy to identify potential donors with optimal vaginal microbiomes. Together, this work lays the foundation for designing safe, reproducible trials of VMT as a treatment for BV.

Vaginal microbial shifts are unaffected by oral pre-exposure prophylaxis in South African women.

Vaginal microbiota have been shown to be a modifier of protection offered by topical tenofovir in preventing HIV infection in women, an effect not observed with oral tenofovir-based pre-exposure prophylaxis (PrEP). It remains unclear whether PrEP can influence the vaginal microbiota composition. This study investigated the impact of daily oral tenofovir disoproxil fumarate in combination with emtricitabine for PrEP on the vaginal microbiota in South African women. At baseline, Lactobacillus iners or Gardnerella vaginalis dominant vaginal communities were observed in the majority of participants. In cross sectional analysis, vaginal microbiota were not affected by the initiation and use of PrEP. Longitudinal analysis revealed that Lactobacillus crispatus-dominant "cervicotypes 1 (CT1)" communities had high probability of remaining stable in PrEP group, but had a higher probability of transitioning to L. iners-dominant CT2 communities in non-PrEP group. L. iners-dominant communities were more likely to transition to communities associated with bacterial vaginosis (BV), irrespective of PrEP or antibiotic use. As expected, BV-linked CTs had a higher probability of transitioning to L. iners than L. crispatus dominant CTs and this shift was not associated with PrEP use.

Preserved Mucosal-Associated Invariant T Cells in the Cervical Mucosa of HIV-Infected Women with Dominant Expression of the TRAV1-2-TRAJ20 T Cell Receptor α-Chain.

BACKGROUND: Mucosa-associated invariant T (MAIT) cells are innate-like T cells with specialized antimicrobial functions. Circulating MAIT cells are depleted in chronic human immunodeficiency virus (HIV) infection, but studies examining this effect in peripheral tissues, such as the female genital tract, are lacking. METHODS: Flow cytometry was used to investigate circulating MAIT cells in a cohort of HIV-seropositive (HIV+) and HIV-seronegative (HIV-) female sex workers (FSWs), and HIV- lower-risk women (LRW). In situ staining and quantitative polymerase chain reaction were performed to explore the phenotype of MAIT cells residing in paired cervicovaginal tissue. The cervicovaginal microbiome was assessed by means of 16S ribosomal RNA gene sequencing. RESULTS: MAIT cells in the HIV+ FSW group were low in frequency in the circulation but preserved in the ectocervix. MAIT cell T-cell receptor gene segment usage differed between the HIV+ and HIV- FSW groups. The TRAV1-2-TRAJ20 transcript was the most highly expressed MAIT TRAJ gene detected in the ectocervix in the HIV+ FSW group. MAIT TRAVJ usage was not associated with specific genera in the vaginal microbiome. CONCLUSIONS: MAIT cells residing in the ectocervix are numerically preserved irrespective of HIV infection status and displayed dominant expression of TRAV1-2-TRAJ20. These findings have implications for understanding the role of cervical MAIT cells in health and disease.

Cysteine dependence of Lactobacillus iners is a potential therapeutic target for vaginal microbiota modulation.

Vaginal microbiota composition affects many facets of reproductive health. Lactobacillus iners-dominated microbial communities are associated with poorer outcomes, including higher risk of bacterial vaginosis (BV), compared with vaginal microbiota rich in L. crispatus. Unfortunately, standard-of-care metronidazole therapy for BV typically results in dominance of L. iners, probably contributing to post-treatment relapse. Here we generate an L. iners isolate collection comprising 34 previously unreported isolates from 14 South African women with and without BV and 4 previously unreported isolates from 3 US women. We also report an associated genome catalogue comprising 1,218 vaginal Lactobacillus isolate genomes and metagenome-assembled genomes from >300 women across 4 continents. We show that, unlike L. crispatus, L. iners growth is dependent on L-cysteine in vitro and we trace this phenotype to the absence of canonical cysteine biosynthesis pathways and a restricted repertoire of cysteine-related transport mechanisms. We further show that cysteine concentrations in cervicovaginal lavage samples correlate with Lactobacillus abundance in vivo and that cystine uptake inhibitors selectively inhibit L. iners growth in vitro. Combining an inhibitor with metronidazole promotes L. crispatus dominance of defined BV-like communities in vitro by suppressing L. iners growth. Our findings enable a better understanding of L. iners biology and suggest candidate treatments to modulate the vaginal microbiota to improve reproductive health for women globally.

Multimodal Investigation of Neuroinflammation in Aviremic Patients With HIV on Antiretroviral Therapy and HIV Elite Controllers.

BACKGROUND AND OBJECTIVES: The presence of HIV in the CNS has been related to chronic immune activation and cognitive dysfunction. The aim of this work was to investigate (1) the presence of neuroinflammation in aviremic people with HIV (PWH) on therapy and in nontreated aviremic PWH (elite controllers [ECs]) using a translocator protein 18 kDa radioligand; (2) the relationship between neuroinflammation and cognitive function in aviremic PWH; and (3) the relationship between [11C]-PBR28 signal and quantitative MRI (qMRI) measures of brain tissue integrity such as T1 and T2 relaxation times (rts). METHODS: [11C]-PBR28 (standard uptake value ratio, SUVR) images were generated in 36 participants (14 PWH, 6 ECs, and 16 healthy controls) using a statistically defined pseudoreference region. Group comparisons of [11C]-PBR28 SUVR were performed using region of interest-based and voxelwise analyses. The relationship between inflammation, qMRI measures, and cognitive function was studied. RESULTS: In region of interest analyses, ECs exhibited significantly lower [11C]-PBR28 signal in the thalamus, putamen, superior temporal gyrus, prefrontal cortex, and cerebellum compared with the PWH. In voxelwise analyses, differences were observed in the thalamus, precuneus cortex, inferior temporal gyrus, occipital cortex, cerebellum, and white matter (WM). [11C]-PBR28 signal in the WM and superior temporal gyrus was related to processing speed and selective attention in PWH. In a subset of PWH (n = 12), [11C]-PBR28 signal in the thalamus and WM regions was related to a decrease in T2 rt and to an increase in T1 rt suggesting a colocalization of increased glial metabolism, decrease in microstructural integrity, and iron accumulation. DISCUSSION: This study casts a new light onto the role of neuroinflammation and related microstructural alterations of HIV infection in the CNS and shows that ECs suppress neuroinflammation more effectively than PWH on therapy.

SARS-CoV-2 RNA Detected in Vitreous Samples Obtained at Autopsy.

Purpose: This work aims to examine the vitreous of autopsy patients with COVID-19 for the presence of SARS-CoV-2 RNA. Methods: Four deceased patients with COVID-19 had an autopsy at Massachusetts General Hospital. Two control specimens were obtained from patients undergoing retinal detachment repair with negative preoperative polymerase chain reaction (PCR) testing for SARS-CoV-2 RNA. Vitreous specimens were obtained from autopsy patients with COVID-19 after povidone was placed on the ocular surface to decrease the risk of contamination of the vitreous specimen. SARS-CoV-2 RNA for gene N (nucleocapsid) was tested using reverse transcription-PCR. Results: SARS-CoV-2 RNA was detected in the vitreous of 2 of 4 autopsy patients who died from complications of COVID-19. Conclusions: SARS-CoV-2 RNA can penetrate into the vitreous of systemically infected patients, which might present risks to operating room personnel during ophthalmic surgical procedures.

Prediction of Antimicrobial Resistance in Clinical Enterococcus faecium Isolates Using a Rules-Based Analysis of Whole-Genome Sequences.

Enterococcus faecium is a major cause of clinical infections, often due to multidrug-resistant (MDR) strains. Whole-genome sequencing (WGS) is a powerful tool to study MDR bacteria and their antimicrobial resistance (AMR) mechanisms. In this study, we used WGS to characterize E. faecium clinical isolates and test the feasibility of rules-based genotypic prediction of AMR. Clinical isolates were divided into derivation and validation sets. Phenotypic susceptibility testing for ampicillin, vancomycin, high-level gentamicin, ciprofloxacin, levofloxacin, doxycycline, tetracycline, and linezolid was performed using the Vitek 2 automated system, with confirmation and discrepancy resolution by broth microdilution, disk diffusion, or gradient diffusion when needed. WGS was performed to identify isolate lineage and AMR genotype. AMR prediction rules were derived by analyzing the genotypic-phenotypic relationship in the derivation set. Phylogenetic analysis demonstrated that 88% of isolates in the collection belonged to hospital-associated clonal complex 17. Additionally, 12% of isolates had novel sequence types. When applied to the validation set, the derived prediction rules demonstrated an overall positive predictive value of 98% and negative predictive value of 99% compared to standard phenotypic methods. Most errors were falsely resistant predictions for tetracycline and doxycycline. Further analysis of genotypic-phenotypic discrepancies revealed potentially novel pbp5 and tet(M) alleles that provide insight into ampicillin and tetracycline class resistance mechanisms. The prediction rules demonstrated generalizability when tested on an external data set. In conclusion, known AMR genes and mutations can predict E. faecium phenotypic susceptibility with high accuracy for most routinely tested antibiotics, providing opportunities for advancing molecular diagnostics.

Fecal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-Cov-2) RNA Is Associated With Decreased Coronavirus Disease 2019 (COVID-19) Survival.

The clinical significance of severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) RNA in stool remains uncertain. We found that extrapulmonary dissemination of infection to the gastrointestinal tract, assessed by the presence of SARS-CoV-2 RNA in stool, is associated with decreased coronavirus disease 2019 (COVID-19) survival. Measurement of SARS-CoV-2 RNA in stool may have utility for clinical risk assessment.

Compartmentalized T cell profile in the lungs of patients with HIV-1-associated pulmonary Kaposi sarcoma.

ABSTRACT: Pulmonary Kaposi sarcoma (pKS) caused by Human herpesvirus 8 (HHV-8) is a devastating form of KS in patients with advanced acquired immunodeficiency syndrome (AIDS) and is associated with increased morbidity and mortality. Blood T cells play a central role in the response of HIV-1 and HHV-8. However, little information is available on T cells in the alveolar space of HIV-1-associated pKS patients.Therefore, we examined CD8+ and CD4+ T cells in the alveolar space in comparison with the blood of patients with pKS. We recruited 26 HIV-1 positive patients with KS, including 15 patients with pKS. Bronchoalveolar lavage (BAL) cells and blood mononuclear cells were analyzed for T cell memory phenotypes, surface markers associated with exhaustion, and intracellular cytokine staining (ICS) using flow cytometry. HIV-1 and HHV-8 viral loads were measured in plasma by quantitative PCR.BAL T cells showed reduced inflammatory capacities and significantly diminished polyfunctionality compared to blood T cells from patients with pKS. This was not accompanied by increased expression of exhaustion markers, such as TIM-3 and PD-1.More importantly, we found a negative correlation between the production of MIP1-ß and TNF-α in T cells in BAL and blood, indicating compartmentalised immune responses to pKS and accentuated chronic HIV-1/HHV-8 pathogenesis via T cells in the lungs of people with pKS.

Reporting guidelines for human microbiome research: the STORMS checklist.

The particularly interdisciplinary nature of human microbiome research makes the organization and reporting of results spanning epidemiology, biology, bioinformatics, translational medicine and statistics a challenge. Commonly used reporting guidelines for observational or genetic epidemiology studies lack key features specific to microbiome studies. Therefore, a multidisciplinary group of microbiome epidemiology researchers adapted guidelines for observational and genetic studies to culture-independent human microbiome studies, and also developed new reporting elements for laboratory, bioinformatics and statistical analyses tailored to microbiome studies. The resulting tool, called 'Strengthening The Organization and Reporting of Microbiome Studies' (STORMS), is composed of a 17-item checklist organized into six sections that correspond to the typical sections of a scientific publication, presented as an editable table for inclusion in supplementary materials. The STORMS checklist provides guidance for concise and complete reporting of microbiome studies that will facilitate manuscript preparation, peer review, and reader comprehension of publications and comparative analysis of published results.