So much more to mucus: Mammals accommodate a dense community of metabolically active microorganisms in their gut. This is not a passive relationship, and host and microbe have antagonistic as well as mutualistic responses to each other. Using a whole-colon imaging method in mice, Bergstrom et al. looked at the role of colonic mucus in segregating the microbiota from host cells during elimination of feces (see the Perspective by Birchenough and Johansson). Host goblet cells synthesize two forms of mucin that differ in branched chain O-glycosylation and the site of production in the colon. A “thick” mucus in the proximal, ascending colon wraps the microbiota to form fecal pellets. Transit along the distal, descending colon is lubricated by “thin” mucus that transiently links with the thick mucus. Normal mucus encapsulation prevents inflammation and hyperplasia and thus is important for maintenance of a healthy gut. Science , this issue p. 467 ; see also p. 402

COVID-19 is a major pandemic facing the world today, which has implications on current microbiome-based treatments such as fecal microbiota transplantation (FMT) used for recurrent Clostridioides difficile infections. The bidirectional relationship between the inhabitants of our gut, the gut microbiota, and COVID-19 pathogenesis, as well as the underlying mechanism involved, must be elucidated in order to increase FMT safety and efficacy. In this perspective, we discuss the crucial cross-talk between the gut microbiota and the lungs, known as the gut–lung axis, during COVID-19 infection, as well as the putative effect of these microorganisms and their functional activity (i.e., short chain fatty acids and bile acids) on FMT treatment. In addition, we highlight the urgent need to investigate the possible impact of COVID-19 on FMT safety and efficacy, as well as instilling stringent screening protocols of donors and recipients during COVID-19 and post-COVID-19 pandemic to produce a cohesive and optimized FMT treatment plan across all centers and in all countries across the globe.

The new era in the design of modern healthy buildings necessitates multidisciplinary research efforts that link principles of engineering and material sciences with those of building biology, in order to better comprehend and apply underlying interactions among design criteria. As part of this effort, there have been an array of studies in relation to the effects of building characteristics on indoor microbiota and their propensity to cause health issues. Despite the abundance of scientific inquiries, limited studies have been dedicated to concomitantly link these effects to the deterioration of ‘structural integrity’ in the building materials. This study focuses on the observed biodeteriorative capabilities of indoor fungi upon the ubiquitous gypsum board material as a function of building age and room functionality within a university campus. We observed that the fungal growth significantly affected the physical (weight loss) and mechanical (tensile strength) properties of moisture-exposed gypsum board samples; in some cases, tensile strength and weight decreased by more than 80%. Such intertwined associations between the biodeterioration of building material properties due to viable indoor fungi, and as a function of building characteristics, would suggest a critical need towards multi-criteria design and optimization of next-generation healthy buildings. Next to structural integrity measures, with a better understanding of what factors and environmental conditions trigger fungal growth in built environment materials, we can also optimize the design of indoor living spaces, cleaning strategies, as well as emergency management measures during probable events such as flooding or water damage.

Adverse childhood experiences (ACEs) encompass negative, stressful, and potentially traumatic events during childhood, impacting physical and mental health outcomes in adulthood. Limited studies suggest ACEs can have short-term effects on children’s gut microbiomes and adult cognitive performance under stress. Nevertheless, the long-term effects of ACEs experienced during adulthood remain unexplored. Thus, this study aimed to assess the long-term effects of ACEs on the gut microbiota of adult nursing students. We employed a multidimensional approach, combining 16S rRNA sequencing, bioinformatics tools, and machine learning to predict functional capabilities. High-ACE individuals had an increased abundance of Butyricimonas spp. and Prevotella spp. and decreased levels of Clostridiales, and Lachnospira spp. Prevotella abundance correlated negatively with L-glutamate and L-glutamine biosynthesis, potentially impacting intestinal tissue integrity. While nursing students with high ACE reported increased depression, evidence for a direct gut microbiota–depression relationship was inconclusive. High-ACE individuals also experienced a higher prevalence of diarrhea. These findings highlight the long-lasting impact of ACEs on the gut microbiota and its functions in adulthood, particularly among nursing students. Further research is warranted to develop targeted interventions and strategies for healthcare professionals, optimizing overall health outcomes.

The intestinal mucus network, primarily composed of O -glycosylated MUC2 mucin polymers, is essential for protecting the gastrointestinal tract from microbial threats. Sialic acid (Sia), a terminal monosaccharide on complex O -glycans, plays a key role in maintaining mucus integrity and is frequently modified by Casd1-dependent O -acetylation ( O Ac). Despite its prevalence, the biological significance of sialic acid O Ac ( O Ac-Sia) modifications in human and murine mucus remains unclear. We hypothesized that O Ac-Sia variants on mucus interact with the microbiota and are required for optimal mucus barrier function and host-microbe homeostasis in the colon. To test this, we profiled O Ac-Sia on human and mouse MUC2 in situ using viral-derived probes with bacterial FISH and confocal microscopy; generated intestinal epithelial cell (IEC)-specific Casd1 null mice (IEC Casd1 ^-/- ); performed sialylomic and O -glycomic HPLC-MS analyses; assessed microbial communities by 16S rRNA sequencing with quantitative microbial profiling (QMP); and evaluated disease susceptibility using DSS colitis and Citrobacter rodentium infection models. Results revealed that both human and murine mucins are extensively O -acetylated and interact with the microbiota, suggesting biological relevance. IEC Casd1 ^-/- mice were viable and displayed a complete loss of mucin O Ac-Sia, indicating Casd1 is the sole contributor to O Ac-status. Unexpectedly, mucus function was intact in IEC Casd1 ^-/- mice, with no difference in structure or quality vs. WT co-housed littermates.16S rRNA analysis showed a modest but significant sex-specific reduction of microbial loads in male IEC Casd1 ^-/- mice, and a clear trend toward reduced Turicibacter spp. vs. WT mice in both male and females, without impacting overall short-chain fatty acid (SCFA) production. DSS treatment led to more severe and extensive tissue damage in IEC Casd1 ^-/- mice. C. rodentium infection led to increased damage in the cecum and distal colon of IEC Casd1 ^-/- mice without affecting pathogen load, suggesting that O Ac-Sia status has a role in tolerance defense. These findings establish intestinal epithelial Sia O -acetylation as a component dispensable for mucus and host-microbe homeostasis at baseline, but important in limiting damage to mucosal inflammatory insults.

Fundamental restoration ecology and community ecology theories can help us better understand the underlying mechanisms of fecal microbiota transplantation (FMT) and to better design future microbial therapeutics for recurrent Clostridium difficile infections (rCDI) and other dysbiosis-related conditions. In a single cohort study, stool samples were collected from donors and rCDI patients one week prior to FMT (pre-FMT) as well as from patients one week following FMT (post-FMT). Using metagenomic sequencing and machine learning methods, our results suggested that the FMT outcome is not only dependent on the ecological structure of the recipients, but also the interactions between the donor and recipient microbiomes, both at the taxonomical and functional levels. Importantly, we observed that the presence of specific bacteria in donors ( Clostridiodes spp., Desulfovibrio spp., Odoribacter spp. and Oscillibacter spp.) and the absence of specific fungi ( Yarrowia spp.) and bacteria ( Wigglesworthia spp.) in recipients prior to FMT could accurately predict FMT success. Our results also suggested a series of interlocked mechanisms for FMT success, including the repair of the disturbed gut microbial ecosystem by transient colonization of nexus species followed by secondary succession of bile acid metabolizers, sporulators, and short chain fatty acid producers. Therefore, a better understanding of such mechanisms can be fundamental key elements to develop adaptive, personalized microbial-based strategies for the restoration of the gut ecosystem. Importance: There have been a number of studies focusing on understanding the underlying mechanisms in FMT treatment, which can accordingly be used for the optimization of future treatments. However, the current scientific lens has mainly had a uni-kingdom major focus on bacteria, leading to the proposition of the existence of FMT “super-donors”. On the contrary, our preliminary study here suggests that FMT is not necessarily a ‘one stool fits all’ approach and that donor-recipient cross-kingdom microbiota interactions, along with their short-term fluctuations in the gut, bring profound implications in FMT success. The results also conceptualize a series of interlocked mechanisms for FMT success, including first repairing the disturbed gut microbial ecosystem by transient species, followed by secondary succession of indigenous or exogenous bile acid metabolizers, sporulators, and short chain fatty acid producers.