The early life gut microbiota in the developmental origins of health & disease, with Dr. Anne Salonen PhD

The early life gut microbiota in the developmental origins of health & disease, with Dr. Anne Salonen PhD

This episode features Dr. Anne Salonen PhD from University of Helsinki (Finland) speaking about her studies on the gut microbiota in early life and how it relates to health and disease. She noted that while mode of delivery (C-section or vaginal birth) is the largest factor affecting microbiota composition for the first weeks and months of life, the immunological and functional microbiota consequences of this are still unknown. However, there appear to be ‘windows of opportunity’ in which microorganisms can influence the development of the immune system, which have lasting consequences for health. Dr. Salonen describes her Finnish HELMi birth cohort, a longitudinal, prospective general population birth cohort, set up to identify factors that modify the gut microbiota and how they relate to child health and wellbeing. Children from 1055 families were sampled frequently in the first 2 years of life and followed as they grew older. The findings confirmed that early-life microbiota composition was a risk factor (among others) for certain diseases as the children developed. Prof. Salonen also described her study on inoculating the infant gut with maternal gut microbiota via milk feeding after C-section birth. They found, in an initial small study, that the gut microbiota of the infants became similar to vaginally born infants. She sees this type of inoculation as a research tool, and says the field will progress toward standardized, reproducible interventions in this area. EPISODE ABBREVIATIONS AND LINKS: * Nature Communications paper showing gut microbiota wellbeing index: Gut microbiota wellbeing index predicts overall health in a cohort of 1000 infants [https://www.nature.com/articles/s41467-024-52561-6] * Paper on HELMi birth cohort showing factors affecting gut microbiota in early life: Sources of gut microbiota variation in a large longitudinal Finnish infant cohort [https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(23)00260-8/fulltext] * Study of maternal fecal microbiota transplantation in infants born by C-section: Maternal Fecal Microbiota Transplantation in Cesarean-Born Infants Rapidly Restores Normal Gut Microbial Development: A Proof-of-Concept Study. [https://pubmed.ncbi.nlm.nih.gov/33007265/] * Microbes inside [https://www.helsinki.fi/en/researchgroups/microbes-inside] (Salonen lab website) ABOUT DR. ANNE SALONEN: Dr. Anne Salonen is a principal investigator and director of the Human Microbiome Research Program at the Medical Faculty, University of Helsinki. Her research is focused on the intestinal microbiota in health and disease, especially in early life and in relation to diet. Dr. Salonen is a PI of the Finnish Health and Early Life Microbiota (HELMI) birth cohort and involved in maternal fecal microbiota transplantation studies in C-section infants. She is the coordinator of the European Innovation Council Pathfinder project on gut microbiota in precision nutrition (fibrematch.eu). Dr. Salonen’s research also entails female reproductive tract microbiota in relation to reproductive outcomes and Human Papilloma Virus (HPV) infection. Research methodology in Salonen laboratory ranges from NGS and other omics technologies to culture-based microbiology of anaerobes, including application and development of bioinformatic tools for microbiome research. More on our research at https://www.helsinki.fi/en/researchgroups/microbes-inside [https://www.helsinki.fi/en/researchgroups/microbes-inside].

Factors affecting infant gut microbiota development, with Prof. Christopher Stewart PhD

This episode features Prof. Christopher Stewart PhD from Newcastle University (UK), speaking about the factors affecting gut microbiota development in both non-preterm and preterm infants. Prof. Stewart started in the field of environmental microbial ecology and then came to work in human microbiome research. He was involved in the landmark TEDDY study, which aimed to find gut microbial markers of type 1 diabetes (T1D). Although no microbial triggers of T1D were identified, the study found a number of factors that impact gut microbiome development: for example, sex, geographical location, and living with furry animals. Still, most of the variation seen in the infant gut microbiota remains unaccounted for. He noted that infants are exposed to both vaginal and gastrointestinal microorganisms during vaginal birth. In C-section-born infants, seeding of the maternal vaginal and gut microbiota may be promising, but current methods are imprecise and safety has not been established. Furthermore, diet takes over as a primary driver of gut microbiota a few weeks after birth. Prof. Stewart talked about human milk oligosaccharides (HMOs), well known to be utilized by bifidobacteria in the infant gut. His lab recently published the surprising finding that Clostridium species can also utilize HMOs – and while at first this was thought to be detrimental for the infant, further investigation showed that the HMO-utilizing Clostridium may lack the genes for producing specific toxins and end up being protective for the infant gut. Together, the microbial community in the gut may use the full suite of HMO substrates reaching the infant gut. Preterm infants are a population that needs more attention. Antibiotics affect their gut microbiomes – often in a negative way, but for the overall benefit of the baby. His lab is currently funded to study how probiotics affect the preterm infant gut microbiota, and to find strategies for more personalized approaches to administering probiotics in this population. EPISODE ABBREVIATIONS AND LINKS: * TEDDY study, revealing factors affecting gut microbiota development between 3 and 46 months of age: Temporal development of the gut microbiome in early childhood from the TEDDY study [https://www.nature.com/articles/s41586-018-0617-x] * Study on how Clostridium species utilize HMOs: Clostridia from preterm infants metabolize human milk oligosaccharides to suppress pathobionts and modulate intestinal function in organoids [https://www.nature.com/articles/s41564-026-02297-4] * Study on how NEC risk is linked with HMOs: Human milk oligosaccharide DSLNT and gut microbiome in preterm infants predicts necrotising enterocolitis [https://gut.bmj.com/content/70/12/2273]  * Publication on how probiotics impact the gut microbiota in preterm infants: Strain-specific impacts of probiotics are a significant driver of gut microbiome development in very preterm infants [https://www.nature.com/articles/s41564-022-01213-w] * Some similar results have come from the CHILD Cohort Study, described here [https://isappscience.org/resource/episode-80-gut-microbiota-development-in-preterm-and-non-preterm-infants/] * Find Prof. Stewart on LinkedIn [https://www.linkedin.com/in/christopher-stewart-329b5a42/], and learn more about his research on this website [https://www.neonatalresearch.net/] ABOUT PROF. CHRISTOPHER STEWART: Professor Christopher Stewart is an internationally recognised leader in human microbiome research. He earned his PhD in Microbial Ecology from Northumbria University (UK), followed by postdoctoral training at Baylor College of Medicine (Houston, Texas), before establishing his research group at Newcastle University in 2018. His pioneering work focuses on microbial-host interactions in the gut, particularly in infants born extremely premature (<32 weeks gestation). His lab integrates multi-omic analyses of clinical samples with experimental microbiology and organoid co-culture systems to uncover mechanisms of microbial influence on early-life development. More recently, he has expanded his research to support a UK-wide initiative investigating microbiome-based predictors of therapeutic response in adult inflammatory bowel disease. Professor Stewart has published over 140 peer-reviewed articles in leading journals, contributing to the discovery of novel biomarkers and targeted microbiome-based interventions. He has received numerous prestigious awards, including the Blavatnik Award for Life Sciences Laureate, the Lister Institute Research Prize, the Microbiology Society Fleming Prize, the NOSTER & Science Microbiome Finalist Prize, the Applied Microbiology International WH Pierce Prize, and the Neonatal Society Rising Star Award.  His research has broad implications for understanding diet–microbe–host interactions and improving health across the life course, miology, maternal and child health, and microbiome science, with a particular emphasis on the effects of vaginal microbiota transfer (VMT) on the microbiota composition and health outcomes of cesarean-delivered infants.

A mechanism linking the newborn skin microbiota to neurodevelopment, with Prof. Rihua Xie and Dr. Yuhang Zhang

This episode features Prof. Rihua Xie from Guangdong Medical University (China) and Dr. Yuhang Zhang from Peking University First Hospital (China), speaking about vaginal microbiota transfer (VMT) and how it may affect neurodevelopment in newborn infants born by Cesarean section. Compared with vaginally delivered infants, C-section delivered infants have altered microbial exposures. VMT has been proposed as a way to ‘restore’ the microbiota of these infants to more closely resemble that of vaginally-born infants. A recent study by Prof. Xie and Dr. Zhang showed that the order and timing of early microbial colonization of the infant is important. They found that VMT could establish a vaginal-like skin microbiota in infants born by C-section, with two particular bacterial species that were higher after VMT. These two species led to the production of metabolites that combined on the newborn’s skin to synthesize an important lipid, which was positively correlated with neurodevelopment scores at three and six months. Subsequent mouse model work showed how this lipid could reach the brain. In the future, safety and standardization of VMT will be important priorities in this research area. Prof. Xie and Dr. Zhang emphasized that their work needs to be replicated in larger cohorts, with the eventual goal of engineering bacteria to create a probiotic intervention that delivers neurodevelopmental benefits to C-section born infants. EPISODE ABBREVIATIONS AND LINKS: * The research by Prof. Xie and Dr. Zhang demonstrating how a VMT intervention alters the skin microbiota of newborns, with a mechanistic link to neurodevelopment: Vaginal microbiota transfer ameliorates cesarean-associated neurodevelopmental deficits in mice via N-bc2S1P synthesis on neonatal skin [https://www.sciencedirect.com/science/article/abs/pii/S1931312826001319] ABOUT PROF. RIHUA XIE: Dr. Ri-hua Xie (RN, PhD, FAAN) is Professor, Principal Investigator, and Chief Nurse at the School of Nursing, Southern Medical University, and the Affiliated Foshan Women and Children Hospital, Guangdong Medical University, China. Dr. Xie is widely recognized for her expertise in maternal and infant health as a clinician, researcher, and supervisor. She has published more than 90 peer-reviewed papers and 11 nursing textbooks and has received 12 competitive research grants from institutions in China and Canada. In addition to her academic work, Dr. Xie is actively engaged in community and public health service, including breastfeeding promotion and frontline support during the COVID-19 pandemic. Her research focuses on perinatal epidemiology, maternal and child health, and microbiome science, with a particular emphasis on the effects of vaginal microbiota transfer (VMT) on the microbiota composition and health outcomes of cesarean-delivered infants. ABOUT DR. YUHANG ZHANG: Yuhang Zhang, PhD in Pharmacology, is an Associate Professor and Principal Investigator at Peking University First Hospital. He received his MD-PhD from Capital Medical University and was a visiting scholar at McGill University, Canada. Dr. Zhang’s research focuses on gut microbiome, probiotics, and microbial metabolism in metabolic diseases, who has published over 20 peer‑reviewed papers as first or corresponding author in journals including Gastroenterology, Journal of Hepatology, and Nature Communications, cited >1,000 times. He has led 9 grants, including the National Natural Science Foundation of China, who was selected for the Beijing Association for Science and Technology Young Talent Program (2022) and the China Association for Science and Technology Young Talent Program (2025). The research of Dr. Zhang focuses on the integrated systems pharmacology, multiomics and microbiome‑host interactions to develop precision medicine.

Gut microbiota development in preterm and non-preterm infants, with Dr. Marie-Claire Arrieta PhD

This episode features Dr. Marie-Claire Arrieta PhD from the University of Calgary (Canada), speaking about development of the early life gut microbiome, both in preterm and non-preterm infants. Across the field, it has been established that the early days and months of an infant’s life are very determinant of immune system development as well as chronic disease later in life. In this period, environmental cues are important, with some of these cues coming from the gut microbiome – both bacteria and fungi. Preterm infants show a very different gut microbiome than non-preterm infants. Ample evidence shows probiotics given to preterm infants can bring clinical benefits such as a reduced risk of necrotizing enterocolitis, but this is separate from investigations into the infants’ gut microbiomes. Dr. Arrieta’s work has shown that probiotics can guide the gut ecosystem of preterm infants toward approximating the non-preterm gut microbiome. One gap in the research is to know more about the effects of specific strains; their work found that although bifidobacteria were more effective at colonizing in the gut, lactobacilli drove some aspects of microbiota maturation. Dr. Arrieta speculates that the case for probiotic use for preterm infants will become stronger as trials increasingly focus on health outcomes not just during the neonatal intensive care unit stay, but also later in life. The CHILD Cohort Study has found that overall in healthy infants, different patterns of gut microbiome and immune development can lead to the appearance of diseases later in life. The latest insight is that disease is linked not to specific microbes or metabolites, but to the pace of gut microbiome development. Misalignment of gut microbiome development (too early or too late) with stages of immune development is associated with later emergence of allergic disease. Several factors such as C-section birth and antibiotics may contribute to this misalignment, but breastfeeding seems to mitigate it. Dr. Arrieta has an ongoing longitudinal study on the early life microbiota and disease associations in preterm and non-preterm infants that is likely to reveal more details. EPISODE ABBREVIATIONS AND LINKS: * Study from Arrieta lab showing effects of a probiotic on the gut microbiome of preterm infants: Supplementation with a probiotic mixture accelerates gut microbiome maturation and reduces intestinal inflammation in extremely preterm infants [https://www.cell.com/cell-host-microbe/fulltext/S1931-3128%2822%2900211-6] * Study combining preterm infant data from several countries, showing links between gut microbiota, immune system development, and late-onset sepsis: Gut microbiota immaturity with DL-endopeptidase deficiency links antibiotic use to preterm late-onset sepsis [https://www.cell.com/cell-host-microbe/fulltext/S1931-3128(26)00049-1] * Arrieta lab website: https://www.arrietalab.com/ [https://www.arrietalab.com/] * Let Them Eat Dirt website with resources for the general public: https://letthemeatdirt.com/ [https://letthemeatdirt.com/] ABOUT DR. MARIE-CLAIRE ARRIETA PHD: Dr. Marie-Claire Arrieta is a Professor and Research Excellence Chair at the Cumming School of Medicine, University of Calgary. Her research examines interactions between the early-life gut microbiome and infant development. Her program integrates clinical and experimental approaches to uncover mechanisms of host–microbiome communication. Her work, published in leading journals, has accumulated over 12,000 citations. She has presented her research internationally through more than 120 invited talks to scientific, medical and public audiences. A dedicated mentor, she has supervised over 45 undergraduate, medical, PhD, and postdoctoral trainees. Her contributions have been recognized with the CIHR-SickKids New Investigator Award, the Killam Emerging Research Leader Award, and election to the College of New Scholars of the Royal Society of Canada. Dr. Arrieta is co-author of the best-selling public book, Let Them Eat Dirt, and is involved in several science communication initiatives.

Toward skin microbiome interventions for anti-aging and wound healing, with Prof. Hariom Yadav PhD

This episode features Prof. Hariom Yadav PhD, from the University of South Florida (USA), speaking about the skin microbiome and potential interventions for anti-aging and wound healing. Prof. Yadav noted that humans have a stable (core) microbiome on the surface of skin cells, plus a transient microbiome that depends on recent exposures. The skin microbiome constantly changes through the lifespan, and in aging, many skin conditions are correlated with the microbiome. Animal studies show a causal component of the microbiome in some of these conditions. However, because of the large skin microbiome differences from person to person and in narrow age groups, technologies or products may have to be designed in a personalized way. Prof. Yadav’s lab conducted experiments with lactobacilli and found strain-dependent effects of probiotics on anti-aging, and for some strains these effects persisted when the inactivated bacteria (postbiotics) were used. The postbiotics have commercial advantages over probiotics in this area of health. Prof. Yadav described an application in wound healing, building on the idea that microbial stimulation promotes natural skin cell growth and more fibroblasts. A standard treatment for wound healing is effective but may lead to scarring; the postbiotic treatment leaves less scarring. The efficacy of the postbiotic occurs because inactivated bacteria still give growth-promoting signals to the skin cells. Applying metabolites directly may not be as effective because bacterial cells or extracts work on host cells, which changes the skin environment and further supports positive skin microbiome changes. Episode abbreviations and links: * Jeffrey Gordon’s landmark paper in 2006: An obesity-associated gut microbiome with increased capacity for energy harvest [https://www.nature.com/articles/nature05414] * Review on the skin microbiome and aging by Prof. Yadav and colleagues: Microbiome-Aging-Wrinkles Axis of Skin: Molecular Insights and Microbial Interventions [https://www.mdpi.com/1422-0067/26/20/10022] * Review on postbiotic skin interventions by Prof. Yadav and colleagues: Microbiome and Postbiotics in Skin Health [https://pmc.ncbi.nlm.nih.gov/articles/PMC12025169/] About Prof. Hariom Yadav PhD: Dr. Hariom Yadav is a Professor at the University of South Florida and Director of the USF Center for Microbiome Research, and co-founder of Postbiotics Inc (www.postbioticsinc.com [http://www.postbioticsinc.com]) and MusB Research (www.musbhealth.com [http://www.musbhealth.com]). With over 25 years of experience, he specializes in microbiome science, biotics, nutrition, longevity, and natural products for optimal wellness. He has authored 200+ peer-reviewed publications, holds/filed 7 patents, mentored over 80 scientists, and has successfully translated multiple innovations into commercially viable products. Dr. Yadav works closely with industry partners to accelerate product development—from discovery and mechanistic validation to clinical trials and regulatory readiness. He leads global collaborative efforts, including the MELLOW (Multi-continental Evidence of Longevity and Lifestyle for Optimal Wellness) consortium, a unique platform for scalable, multi-region clinical validation. His integrated approach enables companies to build scientifically robust, market-ready products with strong differentiation and credibility. He is committed to moving science from bench to market, delivering measurable health impact and commercial success.