Questioning the fetal microbiome illustrates pitfalls of low-biomass microbial studies

Approaching the sterile womb theory in dogs and cats: A multi-technique investigation

The study investigated whether bacterial seeding occurs in utero in dogs and cats using a multi-technique approach, including 16S rRNA gene sequencing, culture, and fluorescence in situ hybridization (FISH). Healthy pregnant bitches and queens (n = 8) undergoing ovariohysterectomy between 30 and 45 days of gestation were included. Placenta and amniotic fluid samples from two foetuses per dam, along with multiple controls (uterine serosa, sampling table, and surgeon's gloves), were collected and analysed. Bacterial sequences were detected in all foetal samples, with no significant differences in intra- and inter-sample diversity (i.e., alpha and beta diversities, respectively) based on sample type or species. However, the surgeon's gloves showed species-specific differences in bacterial composition. After removing control sequences, significant differences based on foeto-maternal units emerged. Moraxella spp. was cultured from the canine placenta with the highest bacterial load, and Burkholderia cepacia was isolated from two feline placentae. FISH showed low bacterial presence in 50 % of placentae without histological signs of inflammation. No bacterial growth was observed in amniotic fluid or control samples. A multi-technique approach, including multiple controls, is essential in studies involving low-biomass samples, as the results of the present study indicated that contamination could mask real bacterial composition of foetal samples. After decontamination, differences were observed based on the foeto-maternal unit. This study confirmed the presence of bacterial DNA in placental and amniotic fluid samples during mid-term, healthy pregnancies in dogs and cats. Bacterial DNA is not equivalent to living bacteria, hence bacterial DNA fragments in the uterus probably originate from the dam but are unlikely to indicate the presence of a resident foetal microbiome.

C-section and systemic inflammation synergize to disrupt the neonatal gut microbiota and brain development in a model of prematurity

Infants born very preterm (below 28 weeks of gestation) are at high risk of developing neurodevelopmental disorders, such as intellectual deficiency, autism spectrum disorders, and attention deficit. Preterm birth often occurs in the context of perinatal systemic inflammation due to chorioamnionitis and postnatal sepsis. In addition, C-section is often performed for very preterm neonates to avoid hypoxia during a vaginal delivery. We have developed and characterized a mouse model based on intraperitoneal injections of IL-1β between postnatal days one and five to reproduce perinatal systemic inflammation. This model replicates several neuropathological, brain imaging, and behavioral deficits observed in preterm infants. We hypothesized that C-sections could synergize with systemic inflammation to induce more severe brain abnormalities. We observed that C-sections significantly exacerbated the deleterious effects of IL-1β on reduced gut microbial diversity, increased levels of circulating peptidoglycans, abnormal microglia/macrophage reactivity, impaired myelination, and reduced functional connectivity in the brain relative to vaginal delivery plus intraperitoneal saline. These data demonstrate the deleterious synergistic effects of C-section and neonatal systemic inflammation on brain maldevelopment and malfunction, two conditions frequently observed in very preterm infants, who are at high risk of developing neurodevelopmental disorders.

Delving the depths of 'terra incognita' in the human intestine - the small intestinal microbiota

The small intestinal microbiota has a crucial role in gastrointestinal health, affecting digestion, immune function, bile acid homeostasis and nutrient metabolism. The challenges of accessibility at this site mean that our knowledge of the small intestinal microbiota is less developed than of the colonic or faecal microbiota. Here, we summarize the features and fluctuations of the microbiota along the small intestinal tract, focusing on humans, and discuss physicochemical factors and assessment methods, including the technical challenges of investigating the low microbial biomass of the proximal small bowel. We highlight the essential protective mechanisms of the small intestine, including motility, the paracellular barrier and mucus, and secretory immunity, to show their roles in limiting excessive exposure of host tissues to microbial metabolites. We address current knowledge gaps, particularly the variability among individuals, the effects of dysbiosis of the small intestinal microbiota on health and how different taxa in small intestinal microbiota could compensate for each other functionally.

Gut feeling: Exploring the intertwined trilateral nexus of gut microbiota, sex hormones, and mental health

The complex interplay between the gut microbiota, sex hormones, and mental health is emerging as a pivotal factor in understanding and managing psychiatric disorders. Beyond their traditional roles, sex hormones exert profound effects on various physiological systems including the gut microbiota. Fluctuations in sex hormone levels, notably during the menstrual cycle, influence gut physiology and barrier function, shaping gut microbiota composition and immune responses. Conversely, the gut microbiota actively modulates sex hormone levels via enzymatic processes. This bidirectional relationship underscores the significance of the gut-brain axis in maintaining mental well-being. This review explores the multifaceted interactions between sex hormones, the gut microbiota, and mental health outcomes. We highlight the potential of personalized interventions in treating psychiatric disorders, particularly in vulnerable populations such as premenopausal women and individuals with depressive disorders. By elucidating these complex interactions, we aim to provide insights for future research into targeted interventions, enhancing mental health outcomes.

Peritoneal fluid microbiota profile of patients with deep endometriosis

Endometriosis is a chronic gynecological disease that affects 10 % of reproductive-aged women and characterized by the presence of endometrial tissue outside the uterus. The disease is linked to a pro-inflammatory environment in the peritoneal fluid of patients, with high levels of cytokines, growth factors, and reactive oxygen species. Changes in the peritoneal fluid, such as altered immune cells and cytokines, can be linked to the immune balance in endometriosis. Immunological changes may be related to the presence of microorganisms in the peritoneal fluid that can activate Toll-like receptor (TLR) signaling and trigger an inflammatory response. A high diversity of TLRs has been found in women with endometriosis, and the presence of specific microorganisms in the fluid is suggested to be responsible for the activation of inflammasomes and inflammatory cytokines involved in the development of endometriosis. The present study was conducted at a hospital in southeastern Brazil to test this hypothesis, using a case-control design. Peritoneal fluid from 50 patients was used in this study. The case group consisted of 27 patients with endometriosis and the control group consisted of 23 patients without endometriosis. The samples were stored in a microbiome transport solution, and DNA was extracted and sent for genetic sequencing to identify the microorganisms present. The obtained sequencing reads were processed using a bioinformatics pipeline involving demultiplexing with the Illumina proprietary software, primer detection and removal, error evaluation, quality filtering, error removal using the Deblur software, amplicon sequence variants grouping, and chimera detection using the VSEARCH software. The sheer abundance of the microbiome made it challenging to discern any notable differences between the two groups. Nevertheless, we highlighted the prevalence of three primary bacteria in the peritoneal fluid from patients with endometriosis: Flavobacterium, Pseudomonas, and Bacillus. The results were established after a rigorous experimental design to eliminate potential contamination from extraction kits and handling. Our findings provide valuable insight into the pathogenesis of this disease and can be useful to understand how microbiota and immune system works in endometriosis.

The Hygienic Significance of Microbiota and Probiotics for Human Wellbeing

The human body can be viewed as a combination of ecological niches inhabited by trillions of bacteria, viruses, fungi, and parasites, all united by the microbiota concept. Human health largely depends on the nature of these relationships and how they are built and maintained. However, personal hygiene practices have historically been focused on the wholesale elimination of pathogens and "hygiene-challenging microorganisms" without considering the collateral damage to beneficial and commensal species. The microbiota can vary significantly in terms of the qualitative and quantitative composition both between different people and within one person during life, and the influence of various environmental factors, including age, nutrition, bad habits, genetic factors, physical activity, medication, and hygienic practices, facilitates these changes. Disturbance of the microbiota is a predisposing factor for the development of diseases and also greatly influences the course and severity of potential complications. Therefore, studying the composition of the microbiota of the different body systems and its appropriate correction is an urgent problem in the modern world. The application of personal hygiene products or probiotics must not compromise health through disruption of the healthy microbiota. Where changes in the composition or metabolic functions of the microbiome may occur, they must be carefully evaluated to ensure that essential biological functions are unaffected. As such, the purpose of this review is to consider the microbiota of each of the "ecological niches" of the human body and highlight the importance of the microbiota in maintaining a healthy body as well as the possibility of its modulation through the use of probiotics for the prevention and treatment of certain human diseases.

MaAsLin 3: Refining and extending generalized multivariable linear models for meta-omic association discovery

A key question in microbial community analysis is determining which microbial features are associated with community properties such as environmental or health phenotypes. This statistical task is impeded by characteristics of typical microbial community profiling technologies, including sparsity (which can be either technical or biological) and the compositionality imposed by most nucleotide sequencing approaches. Many models have been proposed that focus on how the relative abundance of a feature (e.g. taxon or pathway) relates to one or more covariates. Few of these, however, simultaneously control false discovery rates, achieve reasonable power, incorporate complex modeling terms such as random effects, and also permit assessment of prevalence (presence/absence) associations and absolute abundance associations (when appropriate measurements are available, e.g. qPCR or spike-ins). Here, we introduce MaAsLin 3 (Microbiome Multivariable Associations with Linear Models), a modeling framework that simultaneously identifies both abundance and prevalence relationships in microbiome studies with modern, potentially complex designs. MaAsLin 3 also newly accounts for compositionality with experimental (spike-ins and total microbial load estimation) or computational techniques, and it expands the space of biological hypotheses that can be tested with inference for new covariate types. On a variety of synthetic and real datasets, MaAsLin 3 outperformed current state-of-the-art differential abundance methods in testing and inferring associations from compositional data. When applied to the Inflammatory Bowel Disease Multi-omics Database, MaAsLin 3 corroborated many previously reported microbial associations with the inflammatory bowel diseases, but notably 77% of associations were with feature prevalence rather than abundance. In summary, MaAsLin 3 enables researchers to identify microbiome associations with higher accuracy and more specific association types, especially in complex datasets with multiple covariates and repeated measures.

Antibiotic-perturbed microbiota and the role of probiotics

The disruptive effect of antibiotics on the composition and function of the human microbiota is well established. However, the hypothesis that probiotics can help restore the antibiotic-disrupted microbiota has been advanced, with little consideration of the strength of evidence supporting it. Some clinical data suggest that probiotics can reduce antibiotic-related side effects, including Clostridioides difficile-associated diarrhoea, but there are no data that causally link these clinical effects to microbiota protection or recovery. Substantial challenges hinder attempts to address this hypothesis, including the absence of consensus on the composition of a 'normal' microbiota, non-standardized and evolving microbiome measurement methods, and substantial inter-individual microbiota variation. In this Review, we explore these complexities. First, we review the known benefits and risks of antibiotics, the effect of antibiotics on the human microbiota, the resilience and adaptability of the microbiota, and how microbiota restoration might be defined and measured. Subsequently, we explore the evidence for the efficacy of probiotics in preventing disruption or aiding microbiota recovery post-antibiotic treatment. Finally, we offer insights into the current state of research and suggest directions for future research.

Butyrate as a Potential Modulator in Gynecological Disease Progression

This review investigates the therapeutic potential of butyrate, a short-chain fatty acid (SCFA) produced by gut microbiota, in the prevention and treatment of various gynecological diseases, including polycystic ovary syndrome (PCOS), endometriosis, and gynecologic cancers like cervical and ovarian cancer. These conditions often pose treatment challenges, with conventional therapies offering limited and temporary relief, significant side effects, and a risk of recurrence. Emerging evidence highlights butyrate's unique biological activities, particularly its role as a histone deacetylase (HDAC) inhibitor, which allows it to modulate gene expression, immune responses, and inflammation. In PCOS, butyrate aids in restoring hormonal balance, enhancing insulin sensitivity, and reducing chronic inflammation. For endometriosis, butyrate appears to suppress immune dysregulation and minimize lesion proliferation. Additionally, in cervical and ovarian cancers, butyrate demonstrates anticancer effects through mechanisms such as cell cycle arrest, apoptosis induction, and suppression of tumor progression. Dietary interventions, particularly high-fiber and Mediterranean diets, that increase butyrate production are proposed as complementary approaches, supporting natural microbiota modulation to enhance therapeutic outcomes. However, butyrate's short half-life limits its clinical application, spurring interest in butyrate analogs and probiotics to maintain stable levels and extend its benefits. This review consolidates current findings on butyrate's multifaceted impact across gynecological health, highlighting the potential for microbiota-centered therapies in advancing treatment strategies and improving women's reproductive health.

Has the two decades of research on the gut microbiome resulted in making healthier choices?

The gut microbiome is widely recognized for its significant contribution to maintaining human health across all life stages, from infancy to adulthood and beyond. This perspective article focuses on the impacts of well-supported microbiome research on global caesarean delivery rates, breastfeeding practices, and antimicrobial use. The article also explores the impact of dietary choices, particularly those involving ultra-processed foods, on the gut microbiota and their potential contribution to conditions like obesity, metabolic syndrome, and inflammatory diseases. This perspective aims to emphasize the need for updated guidelines and policy interventions to address the increasing global trends of caesarean deliveries, reduced breastfeeding, overuse of antibiotics, and consumption of highly processed foods to counter their adverse effects on gut health.

Unveiling the neonatal gut microbiota: exploring the influence of delivery mode on early microbial colonization and intervention strategies

Recent research has emphasized the critical importance of establishing the neonatal gut microbiota for overall health and immune system development, prompting deeper studies about the early formation of neonatal gut microbiota and its influencing factors. Various factors, including maternal and environmental factors, affect the early formation of neonatal gut microbiota, in which delivery mode has been considered as one of the most crucial influencing factors. In recent years, the increasing trend of cesarean section during childbirth has become a serious challenge for global public health. This review thoroughly analyzes the effects of vaginal delivery and cesarean section on the establishment of neonatal gut microbiota and the potential long-term impacts. In addition, we analyze and discuss interventions such as probiotics, prebiotics, vaginal seeding, fecal microbiota transplantation, and breastfeeding to address the colonization defects of the neonatal gut microbiota caused by cesarean section, aiming to provide theoretical basis for the prevention and treatment of colonization defects and related diseases in infants caused by cesarean section in clinical practice and to provide a theoretical foundation for optimizing the development of neonatal gut microbiota.

Making waves: From tap to gut- exploring the impact of drinking water on gut microbiota

Drinking water (DW) harbours diverse microbial species and chemical attributes. Water comprises the greatest portion of our daily diet, ingested both on its own and used in the preparation of food. DW is our major source of liquids, which is vital to maintaining homeostasis, and can also supply essential minerals. Limited evidence suggests that DW plays a role in shaping the gut microbiome, which implies that it may impact human health. Despite its significant contribution to diet, DW is often overlooked in studies examining dietary influences on the gut microbiota. This perspective explores our current understanding of the link between DW and the gut microbiota - an area of human microbiome science that has been surprisingly understudied. Existing studies reveal links between DW source, microbiota composition, and gut health, emphasizing the need for comprehensive investigations. Understanding the interplay between DW and gut microbiota holds potential for tailored interventions to enhance human health.

Alterations in maternal-fetal gut and amniotic fluid microbiota associated with fetal growth restriction

BACKGROUND

Fetal growth restriction (FGR) is typically characterised as the fetus' inability to reach its inherent growth potential. A growing body of evidence points to the important role of the maternal gut microbiota in FGR development. However, comprehensive research on changes in maternal-fetal gut and intrauterine microbiota related to FGR is lacking.

METHODS

In this case-control study, we sequenced bacterial 16S rRNA from 35 maternal faecal, 35 meconium, and 31 amniotic fluid samples collected from 19 pregnant women diagnosed with FGR and 16 healthy controls. We identified putative bacterial taxonomic and functional characteristics associated with FGR by comparing these to control samples.

RESULTS

We identified 34 differential operational taxonomic units (OTUs) in amniotic fluid, seven differential OTUs in maternal faecal matter, and two differential OTUs in meconium. Compared to controls, FGR subjects exhibited enriched bacterial OTUs of the genus Bacteroides in the maternal gut. They also had depleted OTUs of the order Enterobacterales and genus Pseudomonas in the amniotic fluid and genus Stenotrophomonas in the fetal gut. These altered bacterial OTUs showed a significant correlation with neonatal weight and fetal ultrasonographic indexes. Additionally, we identified differential microbial functional pathways related to glycan and lipid metabolism in the maternal gut. We developed diagnostic biomarkers for FGR based on the maternal-fetal gut and amniotic fluid microbiota.

CONCLUSIONS

This study offers a comprehensive overview of the shifts in microbial composition and functional pathways in the maternal-fetal gut and amniotic fluid microbiota related to FGR, and present novel insights into the development and screening of FGR. However, the assessment of contamination's impact on meconium and amniotic fluid remains inconclusive, necessitating further rigorous experimentation to address this scientific inquiry in future studies.

Gut dysbiosis mediates the association between antibiotic exposure and chronic disease

Antibiotics are safe, effective drugs and continue to save millions of lives and prevent long-term illness worldwide. A large body of epidemiological, interventional and experimental evidence shows that exposure to antibiotics has long-term negative effects on human health. We reviewed the literature data on the links between antibiotic exposure, gut dysbiosis, and chronic disease (notably with regard to the "developmental origins of health and disease" ("DOHaD") approach). Molecular biology studies show that the systemic administration of antibiotic to infants has a rapid onset but also often a long-lasting impact on the microbial composition of the gut. Along with other environmental factors (e.g., an unhealthy "Western" diet and sedentary behavior), antibiotics induce gut dysbiosis, which can be defined as the disruption of a previously stable, functionally complete microbiota. Gut dysbiosis many harmful long-term effects on health. Associations between early-life exposure to antibiotics have been reported for chronic diseases, including inflammatory bowel disease, celiac disease, some cancers, metabolic diseases (obesity and type 2 diabetes), allergic diseases, autoimmune disorders, atherosclerosis, arthritis, and neurodevelopmental, neurodegenerative and other neurological diseases. In mechanistic terms, gut dysbiosis influences chronic disease through direct effects on mucosal immune and inflammatory pathways, plus a wide array of direct or indirect effects of short-chain fatty acids, the enteric nervous system, peristaltic motility, the production of hormones and neurotransmitters, and the loss of intestinal barrier integrity (notably with leakage of the pro-inflammatory endotoxin lipopolysaccharide into the circulation). To mitigate dysbiosis, the administration of probiotics in patients with chronic disease is often (but not always) associated with positive effects on clinical markers (e.g., disease scores) and biomarkers of inflammation and immune activation. Meta-analyses are complicated by differences in probiotic composition, dose level, and treatment duration, and large, randomized, controlled clinical trials are lacking in many disease areas. In view of the critical importance of deciding whether or not to prescribe antibiotics (especially to children), we suggest that the DOHaD concept can be logically extended to "gastrointestinal origins of health and disease" ("GOHaD") or even "microbiotic origins of health and disease" ("MOHaD").

A prenatal skin atlas reveals immune regulation of human skin morphogenesis

Human prenatal skin is populated by innate immune cells, including macrophages, but whether they act solely in immunity or have additional functions in morphogenesis is unclear. Here we assembled a comprehensive multi-omics reference atlas of prenatal human skin (7-17 post-conception weeks), combining single-cell and spatial transcriptomics data, to characterize the microanatomical tissue niches of the skin. This atlas revealed that crosstalk between non-immune and immune cells underpins the formation of hair follicles, is implicated in scarless wound healing and is crucial for skin angiogenesis. We systematically compared a hair-bearing skin organoid (SkO) model derived from human embryonic stem cells and induced pluripotent stem cells to prenatal and adult skin1. The SkO model closely recapitulated in vivo skin epidermal and dermal cell types during hair follicle development and expression of genes implicated in the pathogenesis of genetic hair and skin disorders. However, the SkO model lacked immune cells and had markedly reduced endothelial cell heterogeneity and quantity. Our in vivo prenatal skin cell atlas indicated that macrophages and macrophage-derived growth factors have a role in driving endothelial development. Indeed, vascular network remodelling was enhanced following transfer of autologous macrophages derived from induced pluripotent stem cells into SkO cultures. Innate immune cells are therefore key players in skin morphogenesis beyond their conventional role in immunity, a function they achieve through crosstalk with non-immune cells.

Diagnosing and engineering gut microbiomes

The microbes, nutrients and toxins that we are exposed to can have a profound effect on the composition and function of the gut microbiome. Thousands of peer-reviewed publications link microbiome composition and function to health from the moment of birth, right through to centenarians, generating a tantalizing glimpse of what might be possible if we could intervene rationally. Nevertheless, there remain relatively few real-world examples where successful microbiome engineering leads to beneficial health effects. Here we aim to provide a framework for the progress needed to turn gut microbiome engineering from a trial-and-error approach to a rational medical intervention. The workflow starts with truly understanding and accurately diagnosing the problems that we are trying to fix, before moving on to developing technologies that can achieve the desired changes.

The Existence of an Intra-Amniotic Microbiome: Assessing a Controversy

The existence of intra-amniotic and placental microbiomes during pregnancy has been the source of considerable debate, with research yielding conflicting evidence. This study evaluated investigations into the putative presence of these microbiomes in healthy pregnancies by identifying design and data interpretation issues, particularly concerning contamination in samples with low-density bacterial DNA. Positive findings from diverse populations suggest a consistent presence of microbiota in the intra-amniotic space. Negative conclusions regarding the existence of these prenatal microbiomes emphasise the impact of contamination in the analysis of samples with low-density bacterial DNA. This study concluded that there is no definitive evidence to refute the existence of intra-amniotic microbiomes in healthy pregnancies. Also, it provides suggestions for controlling potential contamination factors in future research on intra-amniotic and placental microbial populations.

Maternal dysbiosis produces long-lasting behavioral changes in offspring

Advanced maternal age (AMA) is defined as a pregnancy in a woman older than 35 years of age. AMA increases the risk for both maternal and neonatal complications, including miscarriage and stillbirth. AMA has also been linked to neurodevelopmental and neuropsychiatric disorders in the offspring. Recent studies have found that age-associated compositional shifts in the gut microbiota contribute to altered microbial metabolism and enhanced inflammation in the host. We investigated the specific contribution of the maternal microbiome on pregnancy outcomes and offspring behavior by recolonizing young female mice with aged female microbiome prior to pregnancy. We discovered that pre-pregnancy colonization of young dams with microbiome from aged female donors significantly increased fetal loss. There were significant differences in the composition of the gut microbiome in pups born from dams recolonized with aged female biome that persisted through middle age. Offspring born from dams colonized with aged microbiome also had significant changes in levels of neurotransmitters and metabolites in the blood and the brain. Adult offspring from dams colonized with an aged microbiome displayed persistent depressive- and anxiety-like phenotypes. Collectively, these results demonstrate that age-related changes in the composition of the maternal gut microbiome contribute to chronic alterations in the behavior and physiology of offspring. This work highlights the potential of microbiome-targeted approaches, even prior to birth, may reduce the risk of neuropsychiatric disorders.

Examining the healthy human microbiome concept

Human microbiomes are essential to health throughout the lifespan and are increasingly recognized and studied for their roles in metabolic, immunological and neurological processes. Although the full complexity of these microbial communities is not fully understood, their clinical and industrial exploitation is well advanced and expanding, needing greater oversight guided by a consensus from the research community. One of the most controversial issues in microbiome research is the definition of a 'healthy' human microbiome. This concept is complicated by the microbial variability over different spatial and temporal scales along with the challenge of applying a unified definition to the spectrum of healthy microbiome configurations. In this Perspective, we examine the progress made and the key gaps that remain to be addressed to fully harness the benefits of the human microbiome. We propose a road map to expand our knowledge of the microbiome-health relationship, incorporating epidemiological approaches informed by the unique ecological characteristics of these communities.

Reduce, reinforce, and replenish: safeguarding the early-life microbiota to reduce intergenerational health disparities

Socioeconomic (SE) disparity and health inequity are closely intertwined and associated with cross-generational increases in the rates of multiple chronic non-communicable diseases (NCDs) in North America and beyond. Coinciding with this social trend is an observed loss of biodiversity within the community of colonizing microbes that live in and on our bodies. Researchers have rightfully pointed to the microbiota as a key modifiable factor with the potential to ease existing health inequities. Although a number of studies have connected the adult microbiome to socioeconomic determinants and health outcomes, few studies have investigated the role of the infant microbiome in perpetuating these outcomes across generations. It is an essential and important question as the infant microbiota is highly sensitive to external forces, and observed shifts during this critical window often portend long-term outcomes of health and disease. While this is often studied in the context of direct modulators, such as delivery mode, family size, antibiotic exposure, and breastfeeding, many of these factors are tied to underlying socioeconomic and/or cross-generational factors. Exploring cross-generational socioeconomic and health inequities through the lens of the infant microbiome may provide valuable avenues to break these intergenerational cycles. In this review, we will focus on the impact of social inequality in infant microbiome development and discuss the benefits of prioritizing and restoring early-life microbiota maturation for reducing intergenerational health disparities.

Clearing the plate: a strategic approach to mitigate well-to-well contamination in large-scale microbiome studies

Large-scale studies are essential to answer questions about complex microbial communities that can be extremely dynamic across hosts, environments, and time points. However, managing acquisition, processing, and analysis of large numbers of samples poses many challenges, with cross-contamination being the biggest obstacle. Contamination complicates analysis and results in sample loss, leading to higher costs and constraints on mixed sample type study designs. While many researchers opt for 96-well plates for their workflows, these plates present a significant issue: the shared seal and weak separation between wells leads to well-to-well contamination. To address this concern, we propose an innovative high-throughput approach, termed as the Matrix method, which employs barcoded Matrix Tubes for sample acquisition. This method is complemented by a paired nucleic acid and metabolite extraction, utilizing 95% (vol/vol) ethanol to stabilize microbial communities and as a solvent for extracting metabolites. Comparative analysis between conventional 96-well plate extractions and the Matrix method, measuring 16S rRNA gene levels via quantitative polymerase chain reaction, demonstrates a notable decrease in well-to-well contamination with the Matrix method. Metagenomics, 16S rRNA gene amplicon sequencing (16S), and untargeted metabolomics analysis via liquid chromatography-tandem mass spectrometry (LC-MS/MS) confirmed that the Matrix method recovers reproducible microbial and metabolite compositions that can distinguish between subjects. This advancement is critical for large-scale study design as it minimizes well-to-well contamination and technical variation, shortens processing times, and integrates with automated infrastructure for enhancing sample randomization and metadata generation.

IMPORTANCE

Understanding dynamic microbial communities typically requires large-scale studies. However, handling large numbers of samples introduces many challenges, with cross-contamination being a major issue. It not only complicates analysis but also leads to sample loss and increased costs and restricts diverse study designs. The prevalent use of 96-well plates for nucleic acid and metabolite extractions exacerbates this problem due to their wells having little separation and being connected by a single plate seal. To address this, we propose a new strategy using barcoded Matrix Tubes, showing a significant reduction in cross-contamination compared to conventional plate-based approaches. Additionally, this method facilitates the extraction of both nucleic acids and metabolites from a single tubed sample, eliminating the need to collect separate aliquots for each extraction. This innovation improves large-scale study design by shortening processing times, simplifying analysis, facilitating metadata curation, and producing more reliable results.

Gestational diabetes exacerbates intrauterine microbial exposure induced intestinal microbiota change in offspring contributing to increased immune response

BACKGROUND

maternal health during pregnancy can affect the intestinal microbial community of offspring, but currently the impact of intrauterine environmental changes resulting from gestational diabetes mellitus (GDM) on the microbiota of offspring as well as its interaction with the immune system remains unclear.

AIMS

to explore the impact of intrauterine microbial exposure during pregnancy of gestational diabetes mellitus on the development of neonate's intestinal microbiota and activation of immune responses.

METHODS

Levels of lipopolysaccharides in cord blood from GDM and expression of microbial recognition-related proteins in the placenta were measured. To evaluate embryonic intestinal colonization, pregnant mice with GDM were administered with labeled Escherichia coli or Lactobacillus. The intestinal colonization of pups was analyzed through 16S rRNA gene sequencing and labeled microbial culture. Additionally, memory T lymphocyte and dendritic cell co-culture experiments were conducted to elucidate the immune memory of intestinal microbes during the embryonic stages.

RESULT

Gestational diabetes mellitus led to elevated umbilical cord blood LPS level and increased GFP labeled Escherichia coli in the offspring's intestine after gestational microbial exposure. The mouse model of GDM exhibited increased immune markers including TLR4, TLR5, IL-22 and IL-23 in the placenta and a recall response from memory T cells in offspring's intestines, with similar observations found in human experiments. Furthermore, reduced intestinal microbiome diversity and an increased ratio of Firmicutes/Bacteroidetes was found in GDM progeny, with the stability of bacterial colonization been interfered.

CONCLUSIONS

Our investigation has revealed a noteworthy correlation between gestational diabetes and intrauterine microbial exposure, as well as alterations in the neonatal microbiota and activation of immune responses. These findings highlight the gestational diabetes's role on offspring's gut microbiota and immune system interactions with early-life pathogen exposure.

Intestinal newborn regulatory B cell antibodies modulate microbiota communities

The role of immunoglobulins produced by IL-10-producing regulatory B cells remains unknown. We found that a particular newborn regulatory B cell population (nBreg) negatively regulates the production of immunoglobulin M (IgM) via IL-10 in an autocrine manner, limiting the intensity of the polyreactive antibody response following innate activation. Based on nBreg scRNA-seq signature, we identify these cells and their repertoire in fetal and neonatal intestinal tissues. By characterizing 205 monoclonal antibodies cloned from intestinal nBreg, we show that newborn germline-encoded antibodies display reactivity against bacteria representing six different phyla of the early microbiota. nBreg-derived antibodies can influence the diversity and the cooperation between members of early microbial communities, at least in part by modulating energy metabolism. These results collectively suggest that nBreg populations help facilitate early-life microbiome establishment and shed light on the paradoxical activities of regulatory B cells in early life.

Intestinal fungal-host interactions in promoting and maintaining health

The resident microbiota are a key component of a healthy organism. The vast majority of microbiome studies have focused on bacterial members, which constitute a significant portion of resident microbial biomass. Recent studies have demonstrated how the fungal component of the microbiota, or the mycobiome, influences mammalian biology despite its low abundance compared to other microbes. Fungi are known for their pathogenic potential, yet fungi are also prominent colonizers in healthy states, highlighting their duality. We summarize the characteristics that define the gut mycobiome across life, the factors that can impact its composition, and studies that identify mechanisms of how fungi confer health benefits. The goal of this review is to synthesize our knowledge regarding the composition and function of a healthy mycobiome with a view to inspiring future therapeutic advances.

What defines a healthy gut microbiome?

The understanding that changes in microbiome composition can influence chronic human diseases and the efficiency of therapies has driven efforts to develop microbiota-centred therapies such as first and next generation probiotics, prebiotics and postbiotics, microbiota editing and faecal microbiota transplantation. Central to microbiome research is understanding how disease impacts microbiome composition and vice versa, yet there is a problematic issue with the term 'dysbiosis', which broadly links microbial imbalances to various chronic illnesses without precision or definition. Another significant issue in microbiome discussions is defining 'healthy individuals' to ascertain what characterises a healthy microbiome. This involves questioning who represents the healthiest segment of our population-whether it is those free from illnesses, athletes at peak performance, individuals living healthily through regular exercise and good nutrition or even elderly adults or centenarians who have been tested by time and achieved remarkable healthy longevity.This review advocates for delineating 'what defines a healthy microbiome?' by considering a broader range of factors related to human health and environmental influences on the microbiota. A healthy microbiome is undoubtedly linked to gut health. Nevertheless, it is very difficult to pinpoint a universally accepted definition of 'gut health' due to the complexities of measuring gut functionality besides the microbiota composition. We must take into account individual variabilities, the influence of diet, lifestyle, host and environmental factors. Moreover, the challenge in distinguishing causation from correlation between gut microbiome and overall health is presented.The review also highlights the resource-heavy nature of comprehensive gut health assessments, which hinders their practicality and broad application. Finally, we call for continued research and a nuanced approach to better understand the intricate and evolving concept of gut health, emphasising the need for more precise and inclusive definitions and methodologies in studying the microbiome.

Cytological evaluation, culture and genomics to evaluate the microbiome in healthy rabbit external ear canals

BACKGROUND

Lop-eared rabbits may be predisposed to otitis externa (OE) as a consequence of their ear conformation. Although otoscopy, otic cytological evaluation and culture are valuable tools in dogs and cats, published data on rabbits remain lacking.

HYPOTHESIS/OBJECTIVES

This study aimed to assess the utility of otoscopy and cytological results in evaluating healthy rabbit external ear canals (EECs) and to characterise ear cytological and microbiological findings through culture techniques and metagenomic sequencing.

ANIMALS

Sixty-three otitis-free client-owned rabbits.

MATERIALS AND METHODS

All rabbits underwent otoscopy and ear cytological evaluation. In a subset of 12 rabbits, further bacterial and fungal culture, fungal DNA assessment and metagenomic sequencing were performed.

RESULTS

Otic cytological results revealed yeast in 73%, cocci in 42.9% and rods in 28.6% of healthy rabbit EECs. Compared to upright-eared rabbits, lop-eared rabbits had more discharge and more bacteria per oil immersion field. Culture isolated eight different species yet metagenomic sequencing identified 36, belonging to the Bacillota (Firmicutes), Pseudomonadota and Actinomycetota phyla. Staphylococcus were the most commonly observed species with both methods. Ten of 12 rabbits were yeast-positive on cytological evaluation with only three yielding fungal growth identified as Yarrowia (Candida) lipolytica, Eurotium echinulatum and Cystofilobasidium infirmominiatum.

CONCLUSIONS AND CLINICAL RELEVANCE

Healthy rabbit EECs lack inflammatory cells yet can host yeast and bacteria, emphasising the need to evaluate cytological results alongside the clinical signs. Lop-ear anatomy may predispose to bacterial overgrowth and OE. Notably, yeasts may be present despite a negative culture.

Female reproductive tract microbiota varies with MHC profile

Numerous studies have shown that a healthy reproductive tract microbiota is crucial for successful reproduction and that its composition is influenced by various environmental and host factors. However, it is not known whether the reproductive microbiota is also shaped by the major histocompatibility complex (MHC), a family of genes essential to differentiate 'self' from 'non-self' peptides to initiate an adaptive immune response. We tested the association between the follicular fluid microbiome and MHC genes in 27 women. Women with higher MHC diversity had a higher microbiome diversity, characterized by bacteria commonly associated with vaginal dysbiosis. Women with similar MHC genes were also similar in their microbiome composition, indicating that MHC composition may be a key factor in determining the bacterial assemblage in the reproductive tract. Finally, the composition of the follicular fluid microbiome was similar to the vaginal microbiome, suggesting that numerous bacteria of the vagina are true inhabitants of the follicular fluid or that vaginal microbiota contaminated the follicular fluid microbiota during transvaginal collection. Collectively, our results demonstrate the importance of host genetic factors in shaping women's reproductive microbiota and they open the door for further research on the role of microbiota in mediating MHC-related variation in reproductive success.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

The influence of pre- and postnatal exposure to air pollution and green spaces on infant's gut microbiota: Results from the MAMI birth cohort study

BACKGROUND

Animal and human studies indicate that exposure to air pollution and natural environments might modulate the gut microbiota, but epidemiological evidence is very scarce.

OBJECTIVES

To assess the potential impact of pre- and postnatal exposure to air pollution and green spaces on infant gut microbiota assembly and trajectories during the first year of life.

METHODS

MAMI ("MAternal MIcrobes") birth cohort (Valencia, Spain, N = 162) was used to study the impact of environmental exposure (acute and chronic) on infant gut microbiota during the first year of life (amplicon-based 16S rRNA sequencing). At 7 days and at 1, 6 and 12 months, residential pre- and postnatal exposure to air pollutants (NO2, black carbon -BC-, PM2.5 and O3) and green spaces indicators (NDVI and area of green spaces at 300, 500 and 1000 m buffers) were obtained. For the association between exposures and alpha diversity indicators linear regression models (cross-sectional analyses) and mixed models, including individual as a random effect (longitudinal analyses), were applied. For the differential taxon analysis, the ANCOM-BC package with a log count transformation and multiple-testing corrections were used.

RESULTS

Acute exposure in the first week of life and chronic postnatal exposure to NO2 were associated with a reduction in microbial alpha diversity, while the effects of green space exposure were not evident. Acute and chronic (prenatal or postnatal) exposure to NO2 resulted in increased abundance of Haemophilus, Akkermansia, Alistipes, Eggerthella, and Tyzerella populations, while increasing green space exposure associated with increased Negativicoccus, Senegalimassilia and Anaerococcus and decreased Tyzzerella and Lachnoclostridium populations.

DISCUSSION

We observed a decrease in the diversity of the gut microbiota and signs of alteration in its composition among infants exposed to higher levels of NO2. Increasing green space exposure was also associated with changes in gut microbial composition. Further research is needed to confirm these findings.

The Role of Metal Nanoparticles in the Pathogenesis of Stone Formation

The process of stone formation in the human body remains incompletely understood, which requires clinical and laboratory studies and the formulation of a new endogenous, nanotechnological concept of the mechanism of origin and formation of crystallization centers. Previously, the mechanism of sialolithiasis was considered a congenital disease associated with the pathology of the ducts in the structure of the glands themselves. To date, such morphological changes of congenital nature can be considered from the position of the intrauterine formation of endogenous bacterial infections complicated by the migration of antigenic structures initiating the formation of crystallization centers. The present work is devoted to the study of the morphology and composition of stones obtained as a result of surgical interventions for sialolithiasis. Presumably, nanoparticles of metals and other chemical compounds can be structural components of crystallization centers or incorporated into the conditions of chronic endogenous inflammation and the composition of antigenic structures, in complexes with protein and bacterial components. X-ray microtomography, X-ray fluorescence analysis, scanning transmission electron microscopy and microanalysis, mass spectrometry, and Raman spectroscopy were used to study the pathogenesis of stone formation. Immunoglobulins (Igs) of classes A and G, as well as nanoparticles of metals Pb, Fe, Cr, and Mo, were found in the internal structure of the stones. The complex of antigenic structures was an ovoid calcified layered matrix of polyvid microbial biofilms, with the inclusion of metal nanoparticles and chemical elements, as well as immunoglobulins. The obtained results of clinical and laboratory studies allow us to broaden the view on the pathogenesis of stone formation and suggest that the occurrence of the calcification of antigenic structures may be associated with the formation of IgG4-associated disease.

Prenatal stress impacts foetal neurodevelopment: Temporal windows of gestational vulnerability

Prenatal maternal stressors ranging in severity from everyday occurrences/hassles to the experience of traumatic events negatively impact neurodevelopment, increasing the risk for the onset of psychopathology in the offspring. Notably, the timing of prenatal stress exposure plays a critical role in determining the nature and severity of subsequent neurodevelopmental outcomes. In this review, we evaluate the empirical evidence regarding temporal windows of heightened vulnerability to prenatal stress with respect to motor, cognitive, language, and behavioural development in both human and animal studies. We also explore potential temporal windows whereby several mechanisms may mediate prenatal stress-induced neurodevelopmental effects, namely, excessive hypothalamic-pituitary-adrenal axis activity, altered serotonin signalling and sympathetic-adrenal-medullary system, changes in placental function, immune system dysregulation, and alterations of the gut microbiota. While broadly defined developmental windows are apparent for specific psychopathological outcomes, inconsistencies arise when more complex cognitive and behavioural outcomes are considered. Novel approaches to track molecular markers reflective of the underlying aetiologies throughout gestation to identify tractable biomolecular signatures corresponding to critical vulnerability periods are urgently required.

Regulation of immune responses to food by commensal microbes

The increasing prevalence of immune-mediated non-communicable chronic diseases, such as food allergies, has prompted a deeper investigation into the role of the gut microbiome in modulating immune responses. Here, we explore the complex interactions between commensal microbes and the host immune system, highlighting the critical role of gut bacteria in maintaining immune homeostasis. We examine how modern lifestyle practices and environmental factors have disrupted co-evolved host-microbe interactions and discuss how changes in microbiome composition impact epithelial barrier function, responses to food allergens, and susceptibility to allergic diseases. Finally, we examine the potential of bioengineered microbiome-based therapies, and live biotherapeutic products, for reestablishing immune homeostasis to prevent or treat food allergies.

Field and laboratory guidelines for reliable bioinformatic and statistical analysis of bacterial shotgun metagenomic data

Shotgun metagenomics is an increasingly cost-effective approach for profiling environmental and host-associated microbial communities. However, due to the complexity of both microbiomes and the molecular techniques required to analyze them, the reliability and representativeness of the results are contingent upon the field, laboratory, and bioinformatic procedures employed. Here, we consider 15 field and laboratory issues that critically impact downstream bioinformatic and statistical data processing, as well as result interpretation, in bacterial shotgun metagenomic studies. The issues we consider encompass intrinsic properties of samples, study design, and laboratory-processing strategies. We identify the links of field and laboratory steps with downstream analytical procedures, explain the means for detecting potential pitfalls, and propose mitigation measures to overcome or minimize their impact in metagenomic studies. We anticipate that our guidelines will assist data scientists in appropriately processing and interpreting their data, while aiding field and laboratory researchers to implement strategies for improving the quality of the generated results.

Delivery mode and maternal gestational diabetes are important factors in shaping the neonatal initial gut microbiota

Background

The infant gut microbiome's establishment is pivotal for health and immune development. Understanding it unveils insights into growth, development, and maternal microbial interactions. Research often emphasizes gut bacteria, neglecting the phageome.

Methods

To investigate the influence of geographic or maternal factors (mode of delivery, mode of breastfeeding, gestational diabetes mellitus) on the gut microbiota and phages of newborns, we collected fecal samples from 34 pairs of mothers and their infants within 24 hours of delivery from three regions (9 pairs from Enshi, 7 pairs from Hohhot, and 18 pairs from Hulunbuir) using sterile containers. Gut microbiota analysis by Shotgun sequencing was subsequently performed.

Results

Our results showed that geographic location affects maternal gut microbiology (P < 0.05), while the effect on infant gut microbiology was not significant (P = 0.184). Among the maternal factors, mode of delivery had a significant (P < 0.05) effect on the newborn. Specific bacteria (e.g., Bacteroides, Escherichia spp., Phocaeicola vulgatus, Escherichia coli, Staphylococcus hominis, Veillonella spp.), predicted active metabolites, and bacteriophage vOTUs varied with delivery mode. Phocaeicola vulgatus significantly correlated with some metabolites and bacteriophages in the early infant gut (P < 0.05). In the GD group, a strong negative correlation of phage diversity between mother and infants was observed (R = -0.58, P=0.04).

Conclusion

In conclusion, neonatal early gut microbiome (including bacteria and bacteriophages) colonization is profoundly affected by the mode of delivery, and maternal gestational diabetes mellitus. The key bacteria may interact with bacteriophages to influence the levels of specific metabolites. Our study provides new evidence for the study of the infant microbiome, fills a gap in the analysis of the infant gut microbiota regarding the virome, and emphasizes the importance of maternal health for the infant initial gut virome.

Planning and Analyzing a Low-Biomass Microbiome Study: A Data Analysis Perspective

As investigations of low-biomass microbial communities have become more common, so too has the recognition of major challenges affecting these analyses. These challenges have been shown to compromise biological conclusions and have contributed to several controversies. Here, we review some of the most common and influential challenges in low-biomass microbiome research. We highlight key approaches to alleviate these potential pitfalls, combining experimental planning strategies and data analysis methods.

In utero human intestine contains maternally derived bacterial metabolites

Understanding when host-microbiome interactions are first established is crucial for comprehending normal development and identifying disease prevention strategies. Furthermore, bacterially derived metabolites play critical roles in shaping the intestinal immune system. Recent studies have demonstrated that memory T cells infiltrate human intestinal tissue early in the second trimester, suggesting that intestinal immune education begins in utero. Our previous study reported a unique fetal intestinal metabolomic profile with an abundance of several bacterially derived metabolites and aryl hydrocarbon receptor (AHR) ligands implicated in mucosal immune regulation. To follow up on this work, in the current study, we demonstrate that a number of microbial byproducts present in fetal intestines in utero are maternally derived and vertically transmitted to the fetus. Notably, these bacterially derived metabolites, particularly short chain fatty acids and secondary bile acids, are likely biologically active and functional in regulating the fetal immune system and preparing the gastrointestinal tract for postnatal microbial encounters, as the transcripts for their various receptors and carrier proteins are present in second trimester intestinal tissue through single-cell transcriptomic data.

Meconium microbiota in naturally delivered canine puppies

BACKGROUND

Microbial colonization during early life has a pivotal impact on the host health, shaping immune and metabolic functions, but little is known about timing and features of this process in dogs. The objectives of this study were to characterize the first step of intestinal microbiota development in naturally delivered canine puppies and to investigate its relationship with the maternal bacterial flora, using traditional culture and molecular analyses. Sixty puppies of two breeds, Appenzeller Cattle Dog (n = 3 dams) and Lagotto Romagnolo (n = 6), housed in the same breeding kennel, were included in the study. Swabs were collected in duplicate (for culture and for molecular analysis) from the dams' vagina and rectum at the end of parturition, from puppies' rectum, before maternal care, and from the environment (floor of the nursery and parturition box).

RESULTS

93.3% meconium samples showed bacterial growth, limited to a few colonies in 57.0% of cases. High growth was detected for Enterococcus faecalis, which was the most frequently isolated bacterium. The genus Enterococcus was one of the most represented in the dams' rectum and vagina (88.9% and 55.6%, respectively). The genera Staphylococcus, Enterococcus, Escherichia and Proteus were also often isolated in meconium but were usually present in maternal samples as well, together with ubiquitous bacteria (Acinetobacter, Psychrobacter). In the environmental samples, just a few bacterial species were found, all with low microbial load. Additionally, bacteria of the phyla Proteobacteria, Firmicutes, and Actinobacteria were identified in meconium through molecular analysis, confirming the culture results and the early colonization of the newborn gut. Maternal, meconium and environmental samples had similar alpha diversity, while beta-diversity showed differences among families (i.e. a dam and her litter), and association indexes revealed a significant correlation between family members and between sample origin, suggesting a strong contribution of the maternal flora to the initial seeding of the canine neonatal gut and a strong individual dam imprint.

CONCLUSION

This study showed that the meconium of vaginally delivered puppies has its own microbiota immediately after birth, and that it is shaped by the dam, which gives a specific imprint to her litter.

The gut microbiota-brain axis in neurological disorders

Previous studies have shown a bidirectional communication between human gut microbiota and the brain, known as the microbiota-gut-brain axis (MGBA). The MGBA influences the host's nervous system development, emotional regulation, and cognitive function through neurotransmitters, immune modulation, and metabolic pathways. Factors like diet, lifestyle, genetics, and environment shape the gut microbiota composition together. Most research have explored how gut microbiota regulates host physiology and its potential in preventing and treating neurological disorders. However, the individual heterogeneity of gut microbiota, strains playing a dominant role in neurological diseases, and the interactions of these microbial metabolites with the central/peripheral nervous systems still need exploration. This review summarizes the potential role of gut microbiota in driving neurodevelopmental disorders (autism spectrum disorder and attention deficit/hyperactivity disorder), neurodegenerative diseases (Alzheimer's and Parkinson's disease), and mood disorders (anxiety and depression) in recent years and discusses the current clinical and preclinical gut microbe-based interventions, including dietary intervention, probiotics, prebiotics, and fecal microbiota transplantation. It also puts forward the current insufficient research on gut microbiota in neurological disorders and provides a framework for further research on neurological disorders.

Arthropods to Eutherians: A Historical and Contemporary Comparison of Sparse Prenatal Microbial Communities Among Animalia Species

Since the advent of next-generation sequencing, investigators worldwide have sought to discern whether a functional and biologically or clinically relevant prenatal microbiome exists. One line of research has led to the hypothesis that microbial DNA detected in utero/in ovo or prior to birth/hatching is a result of contamination and does not belong to viable and functional microbes. Many of these preliminary evaluations have been conducted in humans, mice, and nonhuman primates due to sample and specimen availability. However, a comprehensive review of the literature across animal species suggests organisms that maintain an obligate relationship with microbes may act as better models for interrogating the selective pressures placed on vertical microbial transfer over traditional laboratory species. To date, studies in humans and viviparous laboratory species have failed to illustrate the clear presence and transfer of functional microbes in utero. Until a ground truth regarding the status and relevance of prenatal microbes can be ascertained, it is salient to conduct parallel investigations into the prevalence of a functional prenatal microbiome across the developmental lifespan of multiple organisms in the kingdom Animalia. This comprehensive understanding is necessary not only to determine the role of vertically transmitted microbes and their products in early human health but also to understand their full One Health impact. This review is among the first to compile such comprehensive primary conclusions from the original investigator's conclusions, and hence collectively illustrates that prenatal microbial transfer is supported by experimental evidence arising from over a long and rigorous scientific history encompassing a breadth of species from kingdom Animalia.

The Impact of Gestational Diabetes Mellitus (GDM) on the Development and Composition of the Neonatal Gut Microbiota: A Systematic Review

Gestational diabetes mellitus (GDM) is an important health issue, as it is connected with adverse effects to the mother as well as the fetus. A factor of essence for the pathology of this disorder is the gut microbiota, which seems to have an impact on the development and course of GDM. The role of the gut microbiota on maternal reproductive health and all the changes that happen during pregnancy as well as during the neonatal period is of high interest. The correct establishment and maturation of the gut microbiota is of high importance for the development of basic biological systems. The aim of this study is to provide a systematic review of the literature on the effect of GDM on the gut microbiota of neonates, as well as possible links to morbidity and mortality of neonates born to mothers with GDM. Systematic research took place in databases including PubMed and Scopus until June 2024. Data that involved demographics, methodology, and changes to the microbiota were derived and divided based on patients with exposure to or with GDM. The research conducted on online databases revealed 316 studies, of which only 16 met all the criteria and were included in this review. Research from the studies showed great heterogeneity and varying findings at the level of changes in α and β diversity and enrichment or depletion in phylum, gene, species, and operational taxonomic units in the neonatal gut microbiota of infants born to mothers with GDM. The ways in which the microbiota of neonates and infants are altered due to GDM remain largely unclear and require further investigation. Future studies are needed to explore and clarify these mechanisms.

Development of systemic and mucosal immune responses against gut microbiota in early life and implications for the onset of allergies

The early microbial colonization of human mucosal surfaces is essential for the development of the host immune system. Already during pregnancy, the unborn child is prepared for the postnatal influx of commensals and pathogens via maternal antibodies, and after birth this protection is continued with antibodies in breast milk. During this critical window of time, which extends from pregnancy to the first year of life, each encounter with a microorganism can influence children's immune response and can have a lifelong impact on their life. For example, there are numerous links between the development of allergies and an altered gut microbiome. However, the exact mechanisms behind microbial influences, also extending to how viruses influence host-microbe interactions, are incompletely understood. In this review, we address the impact of infants' first microbial encounters, how the immune system develops to interact with gut microbiota, and summarize how an altered immune response could be implied in allergies.

Inter-kingdom communication and the sympoietic way of life

Organisms are now seen as holobionts, consortia of several species that interact metabolically such that they sustain and scaffold each other's existence and propagation. Sympoiesis, the development of the symbiotic relationships that form holobionts, is critical for our understanding the origins and maintenance of biodiversity. Rather than being the read-out of a single genome, development has been found to be sympoietic, based on multigenomic interactions between zygote-derived cells and symbiotic microbes. These symbiotic and sympoietic interactions are predicated on the ability of cells from different kingdoms of life (e.g., bacteria and animals) to communicate with one another and to have their chemical signals interpreted in a manner that facilitates development. Sympoiesis, the creation of an entity by the interactions of other entities, is commonly seen in embryogenesis (e.g., the creation of lenses and retinas through the interaction of brain and epidermal compartments). In holobiont sympoiesis, interactions between partners of different domains of life interact to form organs and biofilms, wherein each of these domains acts as the environment for the other. If evolution is forged by changes in development, and if symbionts are routinely involved in our development, then changes in sympoiesis can constitute an important factor in evolution.

Bacteria in metastatic sites: Unveiling hidden players in cancer progression

Bacteria exhibit key features of cancer metastasis, such as motility, invasion, and modulation of the tumor microenvironment. They migrate through lymphatic and blood systems, invade metastatic tissues, and alter local microenvironments to support metastatic growth. Bacteria also shape the tumor microenvironment, affecting immune responses and inflammation, which influence tumor progression and therapy response. While they hold therapeutic potential, challenges like contamination and complex characterization persist, necessitating advanced sequencing and research for clinical application.

Tissue-resident bacteria in metabolic diseases: emerging evidence and challenges

Although the impact of the gut microbiome on health and disease is well established, there is controversy regarding the presence of microorganisms such as bacteria and their products in organs and tissues. However, recent contamination-aware findings of tissue-resident microbial signatures provide accumulating evidence in support of bacterial translocation in cardiometabolic disease. The latter provides a distinct paradigm for the link between microbial colonizers of mucosal surfaces and host metabolism. In this Perspective, we re-evaluate the concept of tissue-resident bacteria including their role in metabolic low-grade tissue and systemic inflammation. We examine the limitations and challenges associated with studying low bacterial biomass samples and propose experimental and analytical strategies to overcome these issues. Our Perspective aims to encourage further investigation of the mechanisms linking tissue-resident bacteria to host metabolism and their potentially actionable health implications for prevention and treatment.

Delivery mode is a larger determinant of infant gut microbiome composition at 6 weeks than exposure to peripartum antibiotics

Background. Previous research has shown that delivery mode can shape infant gut microbiome composition. However, mothers delivering by caesarean section routinely receive prophylactic antibiotics prior to delivery, resulting in antibiotic exposure to the infant via the placenta. Previously, only a small number of studies have examined the effect of delivery mode versus antibiotic exposure on the infant gut microbiome with mixed findings.Objective. We aimed to determine the effect of delivery mode compared to antibiotic use during labour and delivery on the infant and maternal gut microbiome at 6 weeks post-partum.Methodology. Twenty-five mother-infant dyads were selected from the longitudinal Queensland Family Cohort Study. The selected dyads comprised nine vaginally delivered infants without antibiotics, seven vaginally delivered infants exposed to antibiotics and nine infants born by caesarean section with routine maternal prophylactic antibiotics. Shotgun-metagenomic sequencing of DNA from stool samples collected at 6 weeks post-partum from mother and infant was used to assess microbiome composition.Results. Caesarean section infants exhibited decreases in Bacteroidetes (ANCOM-BC q<0.0001, MaAsLin 2 q=0.041), changes to several functional pathways and altered beta diversity (R 2=0.056, P=0.029), while minimal differences due to antibiotic exposure were detected. For mothers, caesarean delivery (P=0.0007) and antibiotic use (P=0.016) decreased the evenness of the gut microbiome at 6 weeks post-partum without changing beta diversity. Several taxa in the maternal microbiome were altered in association with antibiotic use, with few differentially abundant taxa associated with delivery mode.Conclusion. For infants, delivery mode appears to have a larger effect on gut microbiome composition at 6 weeks post-partum than intrapartum antibiotic exposure. For mothers, both delivery mode and intrapartum antibiotic use have a small effect on gut microbiome composition at 6 weeks post-partum.

Association between gut microbiota development and allergy in infants born during pandemic-related social distancing restrictions

BACKGROUND

Several hypotheses link reduced microbial exposure to increased prevalence of allergies. Here we capitalize on the opportunity to study a cohort of infants (CORAL), raised during COVID-19 associated social distancing measures, to identify the environmental exposures and dietary factors that contribute to early life microbiota development and to examine their associations with allergic outcomes.

METHODS

Fecal samples were sequenced from infants at 6 (n = 351) and repeated at 12 (n = 343) months, using 16S sequencing. Published 16S data from pre-pandemic cohorts were included for microbiota comparisons. Online questionnaires collected epidemiological information on home environment, healthcare utilization, infant health, allergic diseases, and diet. Skin prick testing (SPT) was performed at 12 (n = 343) and 24 (n = 320) months of age, accompanied by atopic dermatitis and food allergy assessments.

RESULTS

The relative abundance of bifidobacteria was higher, while environmentally transmitted bacteria such as Clostridia was lower in CORAL infants compared to previous cohorts. The abundance of multiple Clostridia taxa correlated with a microbial exposure index. Plant based foods during weaning positively impacted microbiota development. Bifidobacteria levels at 6 months of age, and relative abundance of butyrate producers at 12 months of age, were negatively associated with AD and SPT positivity. The prevalence of allergen sensitization, food allergy, and AD did not increase over pre-pandemic levels.

CONCLUSIONS

Environmental exposures and dietary components significantly impact microbiota community assembly. Our results also suggest that vertically transmitted bacteria and appropriate dietary supports may be more important than exposure to environmental microbes alone for protection against allergic diseases in infancy.

Alterations of the bile microbiome is associated with progression-free survival in pancreatic ductal adenocarcinoma patients

BACKGROUND

Patients with pancreatic ductal adenocarcinoma (PDAC) display an altered oral, gastrointestinal, and intra-pancreatic microbiome compared to healthy individuals. However, knowledge regarding the bile microbiome and its potential impact on progression-free survival in PDACs remains limited.

METHODS

Patients with PDAC (n = 45), including 20 matched pairs before and after surgery, and benign controls (n = 16) were included prospectively. The characteristics of the microbiomes of the total 81 bile were revealed by 16  S-rRNA gene sequencing. PDAC patients were divided into distinct groups based on tumor marker levels, disease staging, before and after surgery, as well as progression free survival (PFS) for further analysis. Disease diagnostic model was formulated utilizing the random forest algorithm.

RESULTS

PDAC patients harbor a unique and diverse bile microbiome (PCoA, weighted Unifrac, p = 0.038), and the increasing microbial diversity is correlated with dysbiosis according to key microbes and microbial functions. Aliihoeflea emerged as the genus displaying the most significant alteration among two groups (p < 0.01). Significant differences were found in beta diversity of the bile microbiome between long-term PFS and short-term PFS groups (PCoA, weighted Unifrac, p = 0.005). Bacillota and Actinomycetota were identified as altered phylum between two groups associated with progression-free survival in all PDAC patients. Additionally, we identified three biomarkers as the most suitable set for the random forest model, which indicated a significantly elevated likelihood of disease occurrence in the PDAC group (p < 0.0001). The area under the receiver operating characteristic (ROC) curve reached 80.8% with a 95% confidence interval ranging from 55.0 to 100%. Due to the scarcity of bile samples, we were unable to conduct further external verification.

CONCLUSION

PDAC is characterized by an altered microbiome of bile ducts. Biliary dysbiosis is linked with progression-free survival in all PDACs. This study revealed the alteration of the bile microbiome in PDACs and successfully developed a diagnostic model for PDAC.

Unveiling the intratumoral microbiota within cancer landscapes

Recent advances in cancer research have unveiled a significant yet previously underappreciated aspect of oncology: the presence and role of intratumoral microbiota. These microbial residents, encompassing bacteria, fungi, and viruses within tumor tissues, have been found to exert considerable influence on tumor development, progression, and the efficacy of therapeutic interventions. This review aims to synthesize these groundbreaking discoveries, providing an integrated overview of the identification, characterization, and functional roles of intratumoral microbiota in cancer biology. We focus on elucidating the complex interactions between these microorganisms and the tumor microenvironment, highlighting their potential as novel biomarkers and therapeutic targets. The purpose of this review is to offer a comprehensive understanding of the microbial dimension in cancer, paving the way for innovative approaches in cancer diagnosis and treatment.

Antimicrobial Peptides (AMPs) and the Microbiome in Preterm Infants: Consequences and Opportunities for Future Therapeutics

Antimicrobial peptides (AMPs) are crucial components of the innate immune system in various organisms, including humans. Beyond their direct antimicrobial effects, AMPs play essential roles in various physiological processes. They induce angiogenesis, promote wound healing, modulate immune responses, and serve as chemoattractants for immune cells. AMPs regulate the microbiome and combat microbial infections on the skin, lungs, and gastrointestinal tract. Produced in response to microbial signals, AMPs help maintain a balanced microbial community and provide a first line of defense against infection. In preterm infants, alterations in microbiome composition have been linked to various health outcomes, including sepsis, necrotizing enterocolitis, atopic dermatitis, and respiratory infections. Dysbiosis, or an imbalance in the microbiome, can alter AMP profiles and potentially lead to inflammation-mediated diseases such as chronic lung disease and obesity. In the following review, we summarize what is known about the vital role of AMPs as multifunctional peptides in protecting newborn infants against infections and modulating the microbiome and immune response. Understanding their roles in preterm infants and high-risk populations offers the potential for innovative approaches to disease prevention and treatment.