Human Vaginal Microbiome Research Articles

The In Vivo Effect of Water-Based Lubricants on the Vaginal Microbiome of Women from Varying Age Groups: Exploratory Analysis of a Randomized Controlled Trial.

Vaginal mucosa undergoes physiological changes across the lifespan, such as increased pH and reduced natural lubrication which are known to impact vaginal commensal microorganisms, hence increasing the chances of vaginal infections. An improved understanding of vaginal microbiome composition in different age groups and the effect of social behaviors, such as the use of personal lubricants, could facilitate the development of new strategies to maintain good vaginal health. The objective of this study was to assess the effect of water-based lubricants on the human vaginal microbiome. Fifty females from three age groups (18-29, 30-44, and 45-65 years) with mild-to-moderate vaginal dryness were randomized to one of five lubricants (four of which were formulated to meet expert guidance on osmolality and pH). Subjects entered the study at tolerance or treatment phase (vaginal intercourse minimum once a week using assigned lubricant). Four vaginal swabs per participant were sampled during pre-("baseline"), post-first ("2 h", "24 h") and post-last ("4 weeks") lubricant application to assess bacterial and fungal diversity via amplicon sequencing. Vaginal pH and relative humidity were measured at baseline, 2 h, and 24 h post-lubricant application. Relative bacteriome abundance was statistically compared between timepoints for each lubricant group. Vaginal moisture, age, BMI, and pH were correlated with bacteriome relative abundance. Lactobacilli and Gardnerella sp. Were predominant across participants. Repeated lubricant application did not significantly alter the vaginal bacteriome during 4 weeks of product use (p > 0.05) when measured by relative abundance and alpha-diversity index. Bacteriome diversity and abundance differed significantly between age groups at baseline whereas lactobacilli relative abundance was negatively associated with age and vaginal pH.

Prevotella are major contributors of sialidases in the human vaginal microbiome

Elevated bacterial sialidase activity in the female genital tract is strongly associated with poor health outcomes including preterm birth and bacterial vaginosis (BV). These negative effects may arise from sialidase-mediated degradation of the protective mucus layer in the cervicovaginal environment. Prior biochemical studies of vaginal bacterial sialidases have focused solely on the BV-associated organism Gardnerella vaginalis. Despite their implications for sexual and reproductive health, sialidases from other vaginal bacteria have not been characterized. Here, we show that vaginal Prevotella species produce sialidases that possess variable activity toward mucin substrates. The sequences of sialidase genes and their presence are largely conserved across clades of Prevotella from different geographies, hinting at their importance globally. Finally, we find that Prevotella sialidase genes and transcripts, including those encoding mucin-degrading sialidases from Prevotella timonensis, are highly prevalent and abundant in human vaginal genomes and transcriptomes. Together, our results identify Prevotella as a critical source of sialidases in the vaginal microbiome, improving our understanding of this detrimental bacterial activity.

A multi-kingdom collection of 33,804 reference genomes for the human vaginal microbiome

The human vagina harbours diverse microorganisms—bacteria, viruses and fungi—with profound implications for women’s health. Genome-level analysis of the vaginal microbiome across multiple kingdoms remains limited. Here we utilize metagenomic sequencing data and fungal cultivation to establish the Vaginal Microbial Genome Collection (VMGC), comprising 33,804 microbial genomes spanning 786 prokaryotic species, 11 fungal species and 4,263 viral operational taxonomic units. Notably, over 25% of prokaryotic species and 85% of viral operational taxonomic units remain uncultured. This collection significantly enriches genomic diversity, especially for prevalent vaginal pathogens such as BVAB1 (an uncultured bacterial vaginosis-associated bacterium) and Amygdalobacter spp. (BVAB2 and related species). Leveraging VMGC, we characterize functional traits of prokaryotes, notably Saccharofermentanales (an underexplored yet prevalent order), along with prokaryotic and eukaryotic viruses, offering insights into their niche adaptation and potential roles in the vagina. VMGC serves as a valuable resource for studying vaginal microbiota and its impact on vaginal health.

Characterizing the vaginal microbiome in a sexually fluid primate (Pan paniscus).

While there have been recent breakthroughs in human vaginal microbiome research, very few non-human primate (NHP) vaginal microbiome studies exist due to difficulty in obtaining samples. In this study, we sought to: (1) characterize the bonobo vaginal microbiota for the first time, and (2) determine the relationship between vaginal pH and swelling size. During a 21-day study period, we collected observational data and 71 vaginal swabs from three cohoused adult females at the Ape Cognition and Conservation Initiative. After filtering and classification, a total of 3452 amplicon sequence variants were recruited from 12 vaginal samples. The most dominant phylum represented was Actinobacteria, and the most abundant genera were Gardnerella, Atopobium, and Prevotella. The mean pH score was 6.1 (range: 5.1-7.0), and pH levels varied with relative swelling size. This is the first study to examine the vaginal microbial composition in this species, and it conforms to previous NHP studies in that there was not the same bacterial dominance of Lactobacillus spp. often highlighted in human vaginal microbiota studies. Our findings suggest there may be other factors contributing to the protection of the bonobo vaginal environment, but future analysis of a larger sample is needed to fully understand how sociality and sexuality shape vaginal microbiota and host health.

Effects of variation in sample storage conditions and swab order on 16S vaginal microbiome analyses.

The composition of the human vaginal microbiome has been linked to a variety of medical conditions including yeast infection, bacterial vaginosis, and sexually transmitted infection. The vaginal microbiome is becoming increasingly acknowledged as a key factor in personal health, and it is essential to establish methods to collect and process accurate samples with self-collection techniques to allow large, population-based studies. In this study, we investigate if using AssayAssure Genelock, a nucleic acid preservative, introduces microbial biases in self-collected vaginal samples. To our knowledge, we also contribute some of the first evidence regarding the impacts of multiple swabs taken at one time point. Vaginal samples have relatively low biomass, so the ability to collect multiple swabs from a unique participant at a single time would greatly improve the replicability and data available for future studies. This will hopefully lay the groundwork to gain a more complete and accurate understanding of the vaginal microbiome.

PSI-18 Vaginal Microbiome of Bos Indicus Cattle in Relation to Fertility

Abstract Shifts in commensal bacteria (e.g., Firmicutes) in the human vaginal microbiome are associated with compromised fertility. The objective of this study was to characterize the reproductive microbiome in the vagina of Bos indicus females prior to fixed-timed artificial insemination (FTAI). Bos indicus females on operations within a 20-mile radius (RANCH 1, RANCH 2, RANCH 3, RANCH 4) were subjected to the 7-day CO-Synch + CIDR protocol on day (d)-9 and FTAI on d0. Sterile vaginal swabs were collected on d-9 (CIDR IN), d-2 (CIDR OUT), and d0 (AI). Cattle were body condition scored (BCS) on d 0. Pregnancy status was determined by transrectal ultrasonography (Non-pregnant, n = 44 and Pregnant, n = 34). Bacterial community analyses were conducted targeting the V4 hypervariable region of the 16S rRNA gene. Data were analyzed using PROC GLM in SAS 9.4. Body condition scores did not differ by pregnancy status or ranch. Additionally, there was no difference in bacterial relative abundance between pregnant or non-pregnant (P > 0.10). The vaginal relative abundance of Firmicutes differed between CIDR IN, CIDR OUT, and AI days (63.54% vs. 28.11% vs. 60.66% ± 1.96%; P < 0.0001). Pregnancy rate did differ by ranch (RANCH 1 63.6% ± 14.7%, RANCH 2 60.0% ± 10.9%, RANCH 3 28.0% ± 9.7%, RANCH 4 36.4% ± 10.4%; P = 0.074). There was a difference observed between ranches with RANCH 4 having the greatest relative abundance of Firmicutes and RANCH 1 having the least (58.84% ± 2.12% vs. 45.12% ± 3.17%; P = 0.0001). A tendency for increased relative abundance of Firmicutes was noted in cows compared with heifers (53.03% ± 1.71% vs. 48.51% ± 1.89%; P = 0.099). Under the phylum of Firmicutes, the genera of Ruminococcus, Clostridium, Blautia, Butyrivibrio, and Mogibacterium followed a similar trend with a shift in relative abundance between CIDR IN, CIDR OUT, and AI days (Table 1). RANCH 1 had the lowest relative abundance of Ruminococcus and Clostridium and the greatest relative abundance of Blautia compared with other ranches (P < 0.05). A shift in relative abundance between CIDR IN, CIDR OUT, and AI days was observed for the phylum of Proteobacteria (7.84% vs. 26.44% vs. 9.69% ± 1.82%; P < 0.0001) and Bacteroidetes (12.19% ± vs. 15.62% vs. 12.67% ± 1.07%; P = 0.046). A tendency for differences in the relative abundance of Bacteroidetes between ranch were observed with RANCH 2 having the greatest relative abundance and RANCH 3 having the least (15.36% ± 1.29% vs. 11.73% ± 1.21%, respectively; P = 0.066). These results suggest a distinct difference in the vaginal microbiome before FTAI. In addition, microbial relative abundances within the vagina also differ between ranches of similar genetics and region.

A new hypothesis on BV etiology: dichotomous and crisscrossing categorization of complex versus simple on healthy versus BV vaginal microbiomes.

BV may influence as many as one-third of women, but its etiology remains unclear. A traditional view is that dominance by Lactobacillus is the hallmark of a healthy vaginal microbiome and lack of dominance may make women BV-prone. Recent studies show that the human VMs can be classified into five major types, four of which possess type-specific dominant species of Lactobacillus. The remaining one (type IV) is not dominated by Lactobacillus and contains a handful of strictly anaerobic bacteria. Nevertheless, exceptions to the first hypothesis have been noticed from the very beginning, and there is not a definite relationship, suggested yet, between the five VM types and BV status. Here, we propose and test a novel hypothesis that assumes the existence of four VM types from dichotomous crisscrossing of "complex versus simple (high diversity or low dominance versus low diversity or high dominance)" on "healthy versus BV." Consequently, there are simple BV versus complex BV.

Transport and Utilization of Glycogen Breakdown Products by Gardnerella spp. from the Human Vaginal Microbiome.

Multiple Gardnerella species frequently cooccur in vaginal microbiomes, and several factors, including competition for nutrients such as glycogen could determine their population structure. Although Gardnerella spp. can hydrolyze glycogen to produce glucose, maltose, maltotriose, and maltotetraose, how these sugars are transported and utilized for growth is unknown. We determined the distribution of genes encoding transporter proteins associated with the uptake of glucose, maltose, and malto-oligosaccharides and maltodextrins among Gardnerella species. A total of five different ABC transporters were identified in Gardnerella spp. of which MusEFGK2I and MalXFGK were conserved across all 15 Gardnerella isolates. RafEFGK and TMSP (trehalose, maltose, sucrose, and palatinose) operons were specific to G. vaginalis while the MalEFG transporter was identified in G. leopoldii only. Although no glucose specific sugar-symporters were identified, putative "glucose/galactose porters" and components of a phosphotransferase system were identified. In laboratory experiments, all Gardnerella isolates grew more in the presence of glucose, maltose, maltotriose, and maltotetraose compared to unsupplemented media. In addition, most isolates (10/15) showed significantly more growth on maltotetraose compared to glucose (Kruskal Wallis, P < 0.05) suggesting their preference for longer chain malto-oligosaccharides. Our findings show that although putative MusEFGK2I and MalXFGK transporters are found in all Gardnerella spp., some species-specific transporters are also present. Observed distribution of genes encoding transporter systems was consistent with laboratory observations that Gardnerella spp. grow better on longer chain malto-oligosaccharides. IMPORTANCE Increased abundance of Gardnerella spp. is a diagnostic characteristic of bacterial vaginosis, an imbalance in the human vaginal microbiome associated with troubling symptoms and negative reproductive health outcomes, including increased transmission of sexually transmitted infections and preterm birth. Competition for nutrients is likely an important factor in causing dramatic shifts in the vaginal microbial community. Gardnerella produces enzymes to digest glycogen, an important nutrient source for vaginal bacteria, but little is known about the mechanisms in Gardnerella for uptake of the products of this digestion, or whether Gardnerella use some or all of the products. Our results indicate that Gardnerella may have evolved to preferentially use a subset of the glycogen breakdown products, which would help them reduce direct competition with some other bacteria in the vagina.

The microRNA Cargo of Human Vaginal Extracellular Vesicles Differentiates Parasitic and Pathobiont Infections from Colonization by Homeostatic Bacteria.

The disturbed vaginal microbiome defined as bacterial vaginosis (BV) and the parasitic infection by Trichomonas vaginalis (TV), the most common non-viral sexually transmitted pathogen, have well-established adverse effects on reproductive outcomes and susceptibility to infection and cancer. Molecular mechanisms underlying these associations and the failure of antibiotic therapy to mitigate adverse consequences are not fully elucidated. In an in vitro human vaginal colonization model, we tested the hypothesis that responses to TV and/or BV-bacteria will disrupt the micro(mi)RNA cargo of extracellular vesicles (EV) with the potential to modify pathways associated with reproductive function, cancer, and infection. miRNAs were quantified by HTG EdgeSeq. MiRNA differential expression (DE) was established in response to TV, the BV signature pathobiont Prevotella bivia and a homeostatic Lactobacillus crispatus with adjusted p < 0.05 using R. Validated gene targets, pathways, protein-protein interaction networks, and hub genes were identified by miRWalk, STRING, Cytoscape, and CytoHubba. In contrast to L. crispatus, TV and the BV pathobiont dysregulated a massive number of EV-miRNAs, over 50% shared by both pathogens. Corresponding target pathways, protein interaction clusters and top hub genes were related to cancer, infectious disease, circadian rhythm, steroid hormone signaling, pregnancy, and reproductive tissue terms. These data support the emerging concept that bacteria and parasitic eukaryotes disturbing the human vaginal microbiome may impact reproductive health through EV-miRNA dysregulation.

Glycogen-Degrading Activities of Catalytic Domains of α-Amylase and α-Amylase-Pullulanase Enzymes Conserved in Gardnerella spp. from the Vaginal Microbiome.

Gardnerella spp. are associated with bacterial vaginosis in which normally dominant lactobacilli are replaced with facultative and anaerobic bacteria, including Gardnerella spp. Co-occurrence of multiple species of Gardnerella is common in the vagina, and competition for nutrients such as glycogen likely contributes to the differential abundances of Gardnerella spp. Glycogen must be digested into smaller components for uptake, a process that depends on the combined action of glycogen-degrading enzymes. In this study, the ability of culture supernatants of 15 isolates of Gardnerella spp. to produce glucose, maltose, maltotriose, and maltotetraose from glycogen was demonstrated. Carbohydrate-active enzymes (CAZymes) were identified bioinformatically in Gardnerella proteomes using dbCAN2. Identified proteins included a single-domain α-amylase (EC 3.2.1.1) (encoded by all 15 isolates) and an α-amylase-pullulanase (EC 3.2.1.41) containing amylase, carbohydrate binding modules, and pullulanase domains (14/15 isolates). To verify the sequence-based functional predictions, the amylase and pullulanase domains of the α-amylase-pullulanase and the single-domain α-amylase were each produced in Escherichia coli. The α-amylase domain from the α-amylase-pullulanase released maltose, maltotriose, and maltotetraose from glycogen, and the pullulanase domain released maltotriose from pullulan and maltose from glycogen, demonstrating that the Gardnerella α-amylase-pullulanase is capable of hydrolyzing α-1,4 and α-1,6 glycosidic bonds. Similarly, the single-domain α-amylase protein also produced maltose, maltotriose, and maltotetraose from glycogen. Our findings show that Gardnerella spp. produce extracellular amylase enzymes as "public goods" that can digest glycogen into maltose, maltotriose, and maltotetraose that can be used by the vaginal microbiota. IMPORTANCE Increased abundance of Gardnerella spp. is a diagnostic characteristic of bacterial vaginosis, an imbalance in the human vaginal microbiome associated with troubling symptoms, and negative reproductive health outcomes, including increased transmission of sexually transmitted infections and preterm birth. Competition for nutrients is likely an important factor in causing dramatic shifts in the vaginal microbial community, but little is known about the contribution of bacterial enzymes to the metabolism of glycogen, a major food source available to vaginal bacteria. The significance of our research is characterizing the activity of enzymes conserved in Gardnerella species that contribute to the ability of these bacteria to utilize glycogen.

Host and Microbiome Interplay Shapes the Vaginal Microenvironment.

The female reproductive tract harbors a unique microbiome, especially the vagina. The human vaginal microbiome exhibits a low diversity and is dominated by Lactobacillus species, compared to the microbiome of other organs. The host and vaginal microbiome mutually coexist in the vaginal microenvironment. Host cells provide Lactobacillus glycogen as an energy source, and Lactobacillus produce lactic acid, which lowers vaginal pH thereby preventing growth of other bacteria. Bacterial vaginosis can modulate host immune systems, and is frequently associated with various aspects of disease, including sexually transmitted infection, gynecologic cancer, and poor pregnancy outcomes. Because of this, numerous studies focused on the impact of the vaginal microbiome on women`s health and disease. Furthermore, numerous epidemiologic studies also have demonstrated various host factors regulate the vaginal microbiome. The female reproductive tract undergoes constant fluctuations due to hormonal cycle, pregnancy, and other extrinsic factors. Depending on these fluctuations, the vaginal microbiome composition can shift temporally and dynamically. In this review, we highlight the current knowledge of how host factors modulate vaginal microbiome composition and how the vaginal microbiome contributes to maintaining homeostasis or inducing pathogenesis. A better understanding of relationship between host and vaginal microbiome could identify novel targets for diagnosis, prognosis, or treatment of microbiome-related diseases.

HIV Pre-exposure Prophylaxis and Its Impact on the Gut Microbiome in Men Having Sex With Men.

HIV/AIDS still imposes a high epidemiological and societal burden. Together with antiretroviral therapy, pre-exposure prophylaxis (PrEP) represents a fundamental tool in the fight against HIV/AIDS. PrEP is considered effective and safe, even though it may affect organs like the kidney, bone, and liver, as shown by randomized clinical trials (RCTs). These side effects may be mediated by alterations of the gut microbiome. Whilst the impact of the human rectal and vaginal microbiome on HIV prevention has been highly investigated among women, less is known about its effect among men having sex with men (MSM), a vulnerable population at high risk for HIV and disproportionately affected by HIV/AIDS. In the present paper, we will overview the effects of PrEP on the gut microbiota in MSM. Mining PubMed/MEDLINE, we identified three studies that have found significant changes affecting the gut microbiota. However, these shifts in the gut microbiome composition are variable, probably due to methodological differences, even though all studies reviewed in the present overview consistently report aberrations at the level of the gut microbiota. More data are needed, especially concerning the long-term side effects of PrEP: despite the studies included being a high-quality RCT, and two well-designed cross-sectional studies, evidence related to the impact of HIV PrEP on the gut microbiome in MSM is scarce and based on small populations. A better understanding of the interactions between the gut microbiota, sexual orientation/identity, and HIV prevention is expected to improve PrEP adherence and devise strategies to counteract PrEP-related side effects.

Models of Murine Vaginal Colonization by Anaerobically Grown Bacteria.

The mammalian vagina can be colonized by many bacterial taxa. The human vaginal microbiome is often dominated by Lactobacillus species, but one-in-four women experience bacterial vaginosis, in which a low level of lactobacilli is accompanied by an overgrowth of diverse anaerobic bacteria. This condition has been associated with many health complications, including risks to reproductive and sexual health. While there is growing evidence showing the complex nature of microbial interactions in human vaginal health, the individual roles of these different anaerobic bacteria are not fully understood. This is complicated by the lack of adequate models to study anaerobically grown vaginal bacteria. Mouse models allow us to investigate the biology and virulence of these organisms in vivo. Other mouse models of vaginal bacterial inoculation have previously been described. Here, we describe methods for the inoculation of anaerobically grown bacteria and their viable recovery in conventionally raised C57Bl/6 mice. A new, less stressful procedural method for vaginal inoculation and washing is also described. Inoculation and viable recovery of Gardnerella are outlined in detail, and strategies for additional anaerobes such as Prevotella bivia and Fusobacterium nucleatum are discussed.

Models of Murine Vaginal Colonization by Anaerobically Grown Bacteria

The mammalian vagina can be colonized by many bacterial taxa. The human vaginal microbiome is often dominated by Lactobacillus species, but one-in-four women experience bacterial vaginosis, in which a low level of lactobacilli is accompanied by an overgrowth of diverse anaerobic bacteria. This condition has been associated with many health complications, including risks to reproductive and sexual health. While there is growing evidence showing the complex nature of microbial interactions in human vaginal health, the individual roles of these different anaerobic bacteria are not fully understood. This is complicated by the lack of adequate models to study anaerobically grown vaginal bacteria. Mouse models allow us to investigate the biology and virulence of these organisms in vivo. Other mouse models of vaginal bacterial inoculation have previously been described. Here, we describe methods for the inoculation of anaerobically grown bacteria and their viable recovery in conventionally raised C57Bl/6 mice. A new, less stressful procedural method for vaginal inoculation and washing is also described. Inoculation and viable recovery of Gardnerella are outlined in detail, and strategies for additional anaerobes such as Prevotella bivia and Fusobacterium nucleatum are discussed.

Unique roles of vaginal Megasphaera phylotypes in reproductive health.

The composition of the human vaginal microbiome has been extensively studied and is known to influence reproductive health. However, the functional roles of individual taxa and their contributions to negative health outcomes have yet to be well characterized. Here, we examine two vaginal bacterial taxa grouped within the genus Megasphaera that have been previously associated with bacterial vaginosis (BV) and pregnancy complications. Phylogenetic analyses support the classification of these taxa as two distinct species. These two phylotypes, Megasphaera phylotype 1 (MP1) and Megasphaera phylotype 2 (MP2), differ in genomic structure and metabolic potential, suggestive of differential roles within the vaginal environment. Further, these vaginal taxa show evidence of genome reduction and changes in DNA base composition, which may be common features of host dependence and/or adaptation to the vaginal environment. In a cohort of 3870 women, we observed that MP1 has a stronger positive association with bacterial vaginosis whereas MP2 was positively associated with trichomoniasis. MP1, in contrast to MP2 and other common BV-associated organisms, was not significantly excluded in pregnancy. In a cohort of 52 pregnant women, MP1 was both present and transcriptionally active in 75.4 % of vaginal samples. Conversely, MP2 was largely absent in the pregnant cohort. This study provides insight into the evolutionary history, genomic potential and predicted functional role of two clinically relevant vaginal microbial taxa.

Associations of urinary microbiome profiles with gestational diabetes mellitus in an Oklahoma case-control study

BACKGROUND AND AIM: Previous research has demonstrated associations between the human placental, gut, and vaginal microbiome and gestational diabetes mellitus (GDM). Recent findings suggest urine is a biomarker for integrated profiling of the genitourinary and amniotic microbiome. However, little is known about how urinary microbiome disturbances may relate to GDM. The present study aims to characterize and compare the urinary microbial profiles among pregnant women with and without GDM. METHODS: Bacterial DNA was extracted from mid-pregnancy urine obtained from a prevalence case-control study of 59 GDM cases and 206 controls from the University of Oklahoma Medical Center (August 2009 to May 2010). The taxonomic profile of the urinary microbiome was characterized by high-throughput sequencing of the V4 region of the microbial 16S rRNA gene. Associations between the microbial composition of taxa relative abundance and GDM were evaluated using multivariable logistic regression while controlling for maternal characteristics. Relative abundance (%) was categorized as absent, ≤median or median values. Alpha diversity (richness and evenness) and beta diversity (community structure) were also compared between cases and controls. RESULTS:A total of 27 microbial genera were identified in the cases and controls, which were predominated by the genera Lactobacillus and Gardnerella. The odds of a relative abundance median was decreased for the genus Aerococcus while it was increased for the genus Veillonella among the cases compared to the controls in the crude model. After adjusting for age and race, GDM cases had a decreased odds of higher relative abundance (median vs. absence) of Aerococcus compared to the controls, with the upper bound of the confidence interval (CI) marginally crossing 1.0 (adjusted odds ratio: 0.45, 95% CI 0.18, 1.10). No difference was observed in alpha and beta diversity metrics between cases and controls. CONCLUSIONS:Our hypothesis-generating results suggest the urinary microbiome composition may differ by GDM status. KEYWORDS: Microbiome, Pregnancy outcomes, Molecular epidemiology

Evaluating the Assembly Dynamics in the Human Vaginal Microbiomes With Niche-Neutral Hybrid Modeling.

Using 2,733 longitudinal vaginal microbiome samples (representing local microbial communities) from 79 individuals (representing meta-communities) in the states of healthy, BV (bacterial vaginosis) and pregnancy, we assess and interpret the relative importance of stochastic forces (e.g., stochastic drifts in bacteria demography, and stochastic dispersal) vs. deterministic selection (e.g., host genome, and host physiology) in shaping the dynamics of human vaginal microbiome (HVM) diversity by an integrated analysis with multi-site neutral (MSN) and niche-neutral hybrid (NNH) modeling. It was found that, when the traditional “default” P-value = 0.05 was specified, the neutral drifts were predominant (≥50% metacommunities indistinguishable from the MSN prediction), while the niche differentiations were moderate (<20% from the NNH prediction). The study also analyzed two challenging uncertainties in testing the neutral and/or niche-neutral hybrid models, i.e., lack of full model specificity – non-unique fittings of same datasets to multiple models with potentially different mechanistic assumptions – and lack of definite rules for setting the P-value thresholds (also noted as Pt-value when referring to the threshold of P-value in this article) in testing null hypothesis (model). Indeed, the two uncertainties can be interdependent, which further complicates the statistical inferences. To deal with the uncertainties, the MSN/NNH test results under a series of P-values ranged from 0.05 to 0.95 were presented. Furthermore, the influence of P-value threshold-setting on the model specificity, and the effects of woman’s health status on the neutrality level of HVM were examined. It was found that with the increase of P-value threshold from 0.05 to 0.95, the overlap (non-unique) fitting of MSN and NNH decreased from 29.1 to 1.3%, whereas the specificity (uniquely fitted to data) of MSN model was kept between 55.7 and 82.3%. Also with the rising P-value threshold, the difference between healthy and BV groups become significant. These findings suggested that traditional single P-value threshold (such as the de facto standard P-value = 0.05) might be insufficient for testing the neutral and/or niche neutral hybrid models.

Human beta defensin levels and vaginal microbiome composition in post-menopausal women diagnosed with lichen sclerosus

Human beta defensins (hBDs) may play an important role in the progression of lichen sclerosus (LS), due to their ability to induce excessive stimulation of extracellular matrix synthesis and fibroblast activation. The genetic ability of the individual to produce defensins, the presence of microbes influencing defensin production, and the sensitivity of microbes to defensins together regulate the formation of an ever-changing balance between defensin levels and microbiome composition. We investigated the potential differences in postmenopausal vaginal microbiome composition and vaginal hBD levels in LS patients compared to non-LS controls. LS patients exhibited significantly lower levels of hBD1 (p = 0.0003), and significantly higher levels of hBD2 (p = 0.0359) and hBD3 (p = 0.0002), compared to the control group. The microbiome of the LS patients was dominated by possibly harmful bacteria including Lactobacillus iners, Streptococcus anginosus or Gardnerella vaginalis known to initiate direct or indirect damage by increasing defensin level production. Our observations highlight that correcting the composition of the microbiome may be applicable in supplementary LS therapy by targeting the restoration of the beneficial flora that does not increase hBD2-3 production.

Characterization of an α-Glucosidase Enzyme Conserved in Gardnerella spp. Isolated from the Human Vaginal Microbiome.

Gardnerella spp. in the vaginal microbiome are associated with bacterial vaginosis, in which a lactobacillus-dominated community is replaced with mixed bacteria, including Gardnerella species. Co-occurrence of multiple Gardnerella species in the vaginal environment is common, but different species are dominant in different women. Competition for nutrients, including glycogen, could play an important role in determining the microbial community structure. Digestion of glycogen into products that can be taken up and further processed by bacteria requires the combined activities of several enzymes collectively known as amylases, which belong to glycoside hydrolase family 13 (GH13) within the CAZy classification system. GH13 is a large and diverse family of proteins, making prediction of their activities challenging. SACCHARIS annotation of the GH13 family in Gardnerella resulted in identification of protein domains belonging to eight subfamilies. Phylogenetic analysis of predicted amylase sequences from 26 genomes demonstrated that a putative α-glucosidase-encoding sequence, CG400_06090, was conserved in all Gardnerella spp. The predicted α-glucosidase enzyme was expressed, purified, and functionally characterized. The enzyme was active on a variety of maltooligosaccharides with maximum activity at pH 7. Km, kcat, and kcat/Km values for the substrate 4-nitrophenyl α-d-glucopyranoside were 8.3 μM, 0.96 min-1, and 0.11 μM-1 min-1, respectively. Glucose was released from maltose, maltotriose, maltotetraose, and maltopentaose, but no products were detected when the enzyme was incubated with glycogen. Our findings show that Gardnerella spp. produce an α-glucosidase enzyme that may contribute to the multistep process of glycogen metabolism by releasing glucose from maltooligosaccharides. IMPORTANCE Increased abundance of Gardnerella spp. is a diagnostic characteristic of bacterial vaginosis, an imbalance in the human vaginal microbiome associated with troubling symptoms, and negative reproductive health outcomes, including increased transmission of sexually transmitted infections and preterm birth. Competition for nutrients is likely an important factor in causing dramatic shifts in the vaginal microbial community but little is known about the contribution of bacterial enzymes to the metabolism of glycogen, a major carbon source available to vaginal bacteria. The significance of our research is characterizing the activity of an enzyme conserved in Gardnerella species that likely contributes to the ability of these bacteria to utilize glycogen.

Comparative metagenomic analysis of the vaginal microbiome in healthy women

The composition of these vaginal microbiome has a significant impact on women's health. However, few studies have characterized the vaginal microbiome of healthy Chinese women using metagenomic sequencing. Here, we carried out a comparative metagenomic analysis to survey taxonomic, functional levels, and microbial communities' genome content in healthy women's vaginal microbiome. Overall, we observed a total of 111 species, including all dominant vaginal Lactobacillus species, such as L. iners, L. crispatus, L. gasseri, and L. jensenii. Unlike microbial taxa, several pathways were ubiquitous and prevalent across individuals, including adenosine ribonucleotides de novo biosynthesis and pyruvate fermentation to acetate and lactate II. Notably, our diversity analysis confirmed a significant difference in healthy women from different ethnic groups. Moreover, we binned vaginal assemblies into 62 high-quality genomes, including 9 L. iners, 7 A. vaginae, 5 L. jensenii, and 5 L. crispatus. We identified the pan and core genomes of L. iners and A. vaginae and revealed the genetic diversity. Primary differences between strains were the hypothetical genes and mobile element-like genes. Our results provide a framework for understanding the implications of the female reproductive tract's composition and functional potential and highlight the importance of genome-resolved metagenomic analysis to further understand the human vaginal microbiome.