npj Biofilms and Microbiomes

Bacteria exhibit two lifestyles: planktonic free-floating individual cells or sessile multicellular aggregates known as biofilms. The biofilm lifecycle is characterised by three distinct stages: attachment, maturation and dispersal. Distinct adaptations occur in each stage, determining cellular behaviours such as surface attachment or synthesis and degradation of extracellular matrix components. Characterising stage-specific bacterial profiles therefore represents a valuable strategy for the development of novel antibiofilm therapies. Here, we used the model biofilm-forming bacterium Pseudomonas aeruginosa PAO1 to characterise the transcriptional profiles of each stage of the biofilm life cycle: attachment, biofilm maturation and spontaneous dispersal in closed cultures. We report that surface attachment was accompanied by the upregulation of genes comprising the Pil-Chp mechanosensory system, whereas biofilm maturation was characterised by the upregulation of genes involved in Pel polysaccharide synthesis, siaD and PA4396 diguanylate cyclases as well as pipA, fimX and PA5442. In contrast, dispersing cells upregulated genes responsible for the biosynthesis of alginate, rhamnolipid, and extracellular nucleases (eddA, eddB), as well as the transcriptional regulator of dispersal amrZ. Additionally, genes encoding the spontaneous dispersal molecule cis-2-decenoic acid (dspS and dspI), canonical phosphodiesterases (nbdA and rbdA), four non-canonical HD-GYP phosphodiesterases and seven other c-di-GMP-related enzymes were also upregulated during dispersal. Our comprehensive analysis of transcriptional changes across biofilm stages therefore provides benchmarking stage-specific transcriptional profiles for P. aeruginosa biofilms in closed culture systems. Furthermore, it allowed the identification of a subset of fourteen genes as transcriptional biomarkers of dispersal, which were used to build reporter plasmids as tools to determine the onset of dispersal. ImportanceBiofilm infections by P. aeruginosa are a major medical challenge due to the increased tolerance to antimicrobials displayed by bacteria living in sessile communities, which is reduced during spontaneous biofilm dispersal. Attachment, biofilm maturation and dispersal represent the main stages of a dynamic process known as the biofilm lifecycle. However, the global regulatory responses governing transitions between these stages remain understudied. Here, we combine live microscopy and biomass quantification to track the progression of P. aeruginosa cultures through the three main stages of the biofilm lifecycle. We show that cells from each stage recapitulate canonical, stage-specific transcriptional responses and identify a set of biomarkers associated with the onset of dispersal. These biomarkers may offer a practical tool for rapidly screening dispersal-inducing compounds, aiding in the discovery of the next generation of antibiofilm therapeutics.

Spatial organization is a defining feature of multispecies biofilms and critically influences microbial interactions and emergent community properties. However, understanding and manipulating how microbes assemble into spatially structured biofilms remains challenging because most experimental frameworks emphasize species composition and pairwise interactions, while often overlooking the spatial constraints on biofilms imposed by the environment. In this study, we focus on how carbon substrate type, distinguishing between diffusible sugars and polymeric substrates, affects biofilm self-organization in a four-member synthetic bacterial community (SynCom). Across all tested conditions, the SynCom consistently formed more biofilm biomass than any of its subsets, indicating a robust synergistic phenotype. Using chemically defined, 3D-printed hydrogel substrates with consistent physical properties, we varied carbon source composition to identify its impact on biofilm assembly. Microscopic imaging showed that carbon substrate type strongly influenced biofilm self-organization with diffusible simple carbon substrates yielding relatively intermixed communities, whereas polymer-rich carbon substrates promoted a highly structured biofilm organization characterized by the dominance and peripheral localization of polymer-degrading species. Bioinformatic analyses of carbohydrate-active enzymes (CAZymes) annotation and genome-scale metabolic modeling suggested that metabolite exchange networks in the SynCom may drive more complex metabolic interactions beyond the commonly observed degrader-exploiter-scavenger relationship within planktonic microbial communities. Together, our findings demonstrate carbon substrate type as an important ecological determinant of biofilm self-organization, highlighting the need to integrate environmental factors alongside species composition and metabolic potential to fully understand and manipulate natural and engineered multispecies biofilms.

1.Fermentable fibres such as inulin can support metabolic health but may exacerbate gastrointestinal symptoms in individuals with irritable bowel syndrome (IBS) due to rapid fermentation and gas production. The gel-forming fibre psyllium improves IBS symptoms, although the underlying mechanisms remain unclear. We hypothesised that fibre gelation alters fermentation by modulating microbial access to substrates. To test this, we compared psyllium with methylcellulose, a chemically modified, gel-forming fibre, to determine the effects of gelation on inulin fermentation. Inulin alone or combined with psyllium or methylcellulose was fermented for 48 hrs in a colonic fermentation model inoculated with healthy human faeces. Gas production, metabolite profiles, microbial community composition and microbial localisation within fibre gels were assessed. Bioactivity of fermentation products was evaluated in STC-1 cells. Psyllium co-fermentation significantly accelerated fermentation and enhanced production of metabolites, while methylcellulose had minimal effects. Psyllium maintained higher diversity and enriched polysaccharide-degrading taxa including Bacteroides and Phoecaeicola species, which were strongly associated with metabolic activity. Bacterial penetration into the psyllium matrix was observed but not into methylcellulose. Fermentation products from psyllium but not methylcellulose stimulated GLP-1 and 5-HT secretion in STC-1 cells. These findings demonstrate that delayed-onset fermentable gel-forming fibres enhance microbial access to entrapped substrates, driving metabolic and hormonal responses.

Foods are spatially structured and heterogeneous matrices in which microbial pathogens predominantly grow as immobilised microcolonies rather than planktonic free cells. However, most predictive microbiology and risk assessment models rely on homogeneous liquid cultures, potentially overlooking spatial effects on stress adaptation. Here, we investigated how growth within food-like semi-solid matrices influences stress adaptation and digestive tolerance of major foodborne pathogens. We compared planktonic and spatialised lifestyles across multiple species exposed to salt and organic acid stresses. Spatial growth profoundly altered growth dynamics in a stress- and species-dependent manner. Notably, spatial growth markedly enhanced tolerance to simulated gastrointestinal stresses in vitro, particularly under acidic conditions. This protective effect was further confirmed in vivo within the acidic midgut of Hermetia illucens larvae. Our findings demonstrate that spatial organisation generates distinct physiological states that increase pathogen resilience, highlighting the need to integrate spatialisation into predictive models and quantitative microbial risk assessment.

Periodontitis is a chronic inflammatory disease associated with dysbiotic microbial communities that leads to destruction of the tooth-supporting tissues. The transition from host-microbial periodontal homeostasis to disease remains poorly understood. The murine ligature-induced periodontitis model was employed to characterize the temporal dynamics of the subgingival microbiome and host tissue features. Ligatures were placed in C57BL/6N mice, and collected on days 0, 1, 3, 5, and 7 post-induction. Bacterial load, alveolar bone loss, immune cells (CD45), cells with osteoclastogenic potential (TRAP) and collagen destruction were analyzed. Additionally, the V4 region of the 16S rRNA gene was sequenced for ecological analyses, including co-occurrence networks and functional prediction. Spatial distribution of the most abundant species was visualized using CLASI-FISH microscopy. Finally, association models were performed to link bacterial abundances with time and tissue parameters. The most substantial microbial shift occurred on day 1, and a dysbiotic community was established by day 3. CD45 cell infiltration increased as early as day 1, preceding the rise in TRAP cells on day 3 and the onset of tissue destruction on day 5. By day 7, predicted bacterial functions included protein export, lipid and galactose metabolism. Health-associated taxa were identified, and their abundance correlated positively with collagen integrity and negatively with immune cell infiltration and bacterial load, highlighting their role in homeostasis. These findings provide a high-resolution temporal map of microbiome-host interactions during experimental periodontitis establishment and identify specific microbial and cellular windows for potential therapeutic intervention.

The cervicovaginal microbiome is pivotal to reproductive health, yet its dynamics in HPV-negative women with gynaecological disorders remain underexplored. We investigated microbial diversity and taxonomic shifts in HPV-negative women from Bangladesh using 16S rRNA gene sequencing and shotgun metagenomics. Of 224 women screened, 136 were HPV-negative; 29 underwent 16S profiling, and three infertility-associated cases were further analyzed by shotgun metagenomics. Healthy controls exhibited low alpha diversity and a Lactobacillus-dominated profile (98.2%), reflecting ecological stability. In contrast, pathological cases displayed significantly elevated richness and evenness, reduced Lactobacillus (28.0%), and enrichment of anaerobic and opportunistic taxa, including Bifidobacterium (23.4%), Achromobacter (12.9%) and Sneathia (7.5%). Distinct microbial signatures emerged across clinical subgroups: pelvic inflammatory disease was enriched in Bifidobacterium, intra-menstrual bleeding retained moderate Lactobacillus, while infertility exhibited prominent dominance of Achromobacter (45.5%). Shotgun metagenomics confirmed Achromobacter spp. (A. ruhlandii, A. dolens, A. xylosoxidans) as the predominant taxa (84.9%) in infertility cases, accompanied by depletion of protective Lactobacillus. Functional inference revealed conserved metabolic backbones but disease-specific enrichment of stress-response and biosynthetic pathways, particularly in infertility and PID. Co-occurrence network analysis identified condition-specific microbial consortia, with Achromobacter forming infertility-associated clusters. This study represents the first integrated application of amplicon and shotgun metagenomic approaches to profile the cervicovaginal microbiota in HPV-negative women. It identifies Achromobacter as a potential microbial biomarker of infertility and highlights the urgent need for microbiome-informed diagnostics and targeted interventions to restore cervicovaginal homeostasis.

Purpose The human extracellular matrix (ECM) provides essential cues for intestinal homeostasis. While most studies focus on ECM degradation by host cells, our prior work suggests that commensal gut microbes may also contribute to these remodeling processes. Here, we continue exploring this novel dimension of host-microbe interactions by profiling the proteolytic diversity and substrate-specific activity of ECM-targeting enzymes across species of Bacteroides, a dominant and metabolically versatile gut genus. MethodsWe curated a custom ECM-specific enzyme database from the BRENDA repository and used it to perform comparative genomic analyses across 11 Bacteroides species, mapping the diversity and abundance of candidate ECM-degrading proteases and carbohydrate active enzymes (CAZymes). Functional activity was evaluated via in vitro degradation assays using purified substrates. Family-specific protease inhibitors were used to confirm the major catalytic classes involved. ResultsECM-targeting CAZymes and proteases were broadly encoded across all 11 genomes, with gene counts positively correlated with genome size and GAG-associated genes comprising the largest substrate category. Experimental degradation assays revealed species- and substrate-specific activity patterns, including elastin degradation restricted to a subset of species, a capacity previously undocumented in intestinal Bacteroides. Genomic predictions showed limited concordance with measured enzymatic activity, suggesting context-dependent regulation of ECM-degrading enzymes. Inhibitor experiments confirmed that collagen degradation is driven primarily by metalloproteases and secondarily by serine proteases across representative species. ConclusionsOur findings position commensal Bacteroides as a rich, yet underappreciated, source of ECM-degrading enzymes. This work underscores the need to consider microbiota as key modulators of host tissue homeostasis and potential targets for therapeutic modulation. BIOGRAPHYDr. Ana Maria Porras is an Assistant Professor of Biomedical Engineering at the University of Florida, where she leads the Tissue-Microbe Interactions lab. Her group leverages cell and tissue engineering, bioinformatics, and statistical modeling to understand how microorganisms regulate human extracellular matrix remodeling. Her work centers primarily on the gut microbiome, cardiovascular health, and tropical infectious diseases. Dr. Porras is also a science artist, and a science communicator, particularly in interested in evidence-based, culturally informed, and multilingual practices to improve public engagement with science. She is the co-founder and Senior Advisor of the Latinx in Biomedical Engineering community, and the recipient of multiple awards, including the UF Excellence Award for Assistant Professors, the NSF Faculty Early Career Development (CAREER) Award, the NIH Maximizing Investigators Research Award (MIRA), the AAAS Early Career Award for Public Engagement with Science, and and the Rising Star Award from the Academy of Science, Engineering, and Medicine of Florida. Prior to arriving in Florida, Dr. Porras was a Presidential Postdoctoral Fellow at Cornell University. She holds a B.S. in biomedical engineering from the University of Texas at Austin, and a Ph.D. from the University of Wisconsin-Madison, where she was an American Heart Association Predoctoral Fellow.

Bacteria use diverse mechanisms to interact with each other and with eukaryotic hosts, thereby shaping microbiome composition and influencing host health. One of these mechanisms is the production of outer membrane vesicles (OMVs), nanoscale structures that bud off from bacterial cells into the extracellular space. OMVs can deliver bioactive cargoes, including enzymes, RNA and DNA, enabling functions such as cell-to-cell communication, nutrient acquisition and immunomodulation. However, the role of OMVs in beneficial host-associated microbiomes remains unclear. Here, we investigated OMV production in the gut bacteria of the western honey bee (Apis mellifera), which forms a highly conserved and stable microbial community. Using electron microscopy, fluorescence labelling, and nanoparticle tracking analysis, we detected OMV production in every gram-negative species of the bee gut microbiota that we investigated. Vesicles were observed in gut contents of wild and laboratory-inoculated bees, but absent in bees lacking a microbiota. OMVs contained nucleic acids, with more RNA than DNA. Bacterial strains varied in OMV properties, including abundance, size, and zeta potential. These findings indicate that OMVs are likely significant mediators of interbacterial and host-microbe interactions in the bee gut.

Colonisation of plastic surfaces by microbial biofilms offers a promising starting point for engineering efficient biodegradation systems. However, most studies to date focus on characterisation or prevention of biofilms on plastics in diverse environments and the potential biotechnological application for these systems has been underexplored. To address this, we report the efficient adhesion of Escherichia coli cells to a range of plastic surfaces through overexpression of two key determinants of bacterial biofilm formation; curli and Antigen 43 (Ag43). A general trend of higher total biomass was observed from curli-mediated adhesion, but more uniform adhesion from Ag43 overexpression. We further demonstrate application of this technology through inducible adhesion of E. coli to polyethylene terephthalate (PET) surfaces and concurrent secretion of the PET depolymerase PHL7. Co-overexpression of curli fibres and secreted PHL7 resulted in 5.6-fold increase in terephthalic acid release in comparison to the non-adherent control. These methods offer a general approach to programmable adhesion of genetically tractable cells to plastic surfaces and concurrent secretion of degradative enzymes, and are anticipated to be broadly applicable across the field of plastic bioremediation technologies.

The human duodenum harbours a complex, dynamic microbial community that is challenging to study due to inaccessibility, particularly postprandially when nutrient-rich chyme and fluctuating metabolites create unique microbial niches. We used naso-duodenal intubation to longitudinally sample duodenal luminal contents following pea-based meals of differing food structure, alongside parallel blood collection. Shotgun metagenomic sequencing, comprehensive metabolomic profiling and gut hormone measurements were combined to explore microbe-metabolite-hormone interactions. Food structure significantly affected postprandial bacterial composition, with saccharolytic oral taxa increasing after meals with intact structure. Alpha diversity was influenced by structure type (P = 0.025), with whole pea seeds promoting greater diversity than pea flour. Network analysis revealed complex interactions between the duodenal microbiome, luminal metabolites and gut hormones, with most microbial associations linked to glucose-dependent insulinotropic polypeptide (GIP) rather than glucagon-like peptide-1 (GLP-1). Metabolic profiling showed meal-dependent changes in amino acid metabolism, including shifts in D/L amino acid ratios over time consistent with microbial metabolism. The duodenal microbiome showed close phylogenetic relationships with the oral microbiome, with composition influenced by food structuring and swallowing. These findings reveal dynamic microbe-metabolite interplay in the human duodenum during digestion and its relationship to gut hormone responses.

Staphylococcus aureus is a leading cause of biofilm-associated infections, in which communities of bacterial cells are encased in an extracellular matrix composed of polysaccharides, proteins, and extracellular DNA (eDNA) that protect bacteria from host immune defense and antibiotics. Despite their importance, the mechanisms by which matrix components are released from bacterial cells and incorporated into the biofilm matrix remain poorly understood. Using a drip-flow biofilm system, we showed that MVs were associated with the biofilm matrix formed by S. aureus clinical isolate MN8. Proteomic analysis of biofilm matrix proteins and purified MVs showed that biofilm-derived MVs carried cytoplasmic, membrane, and extracellular proteins that closely resembled the protein composition of the biofilm matrix but differed significantly from MVs produced by planktonic cultures. Biofilm-derived MVs carried significantly higher levels of DNA than MVs from planktonic cultures, and MV-associated DNA was resistant to DNase treatment. Although strain MN8 is known to form polysaccharide-dependent biofilms, exogenously added DNase or proteinase K significantly impaired biofilm formation and integrity. Notably, these inhibitory effects were reversed by the addition of biofilm-derived MVs, which significantly restored biofilm formation in enzyme-treated cultures. Together, these findings provide evidence that S. aureus MVs are generated within biofilms, and that these MVs serve as an important resource of matrix components and contribute to biofilm formation. ImportanceExtracellular membrane vesicles (MVs) are important mediators of intercellular communication and have been implicated in the physiology and pathogenesis of bacterial infections. While MV production in S. aureus planktonic cultures has been recognized for over one decade, their presence and function in S. aureus biofilm formation have remained unexplored. Here, we report for the first time the purification and characterization of MVs derived from S. aureus biofilms. Our studies demonstrate that S. aureus MVs are important components of the biofilm matrix that contribute to biofilm formation by serving as key carriers of matrix proteins and eDNA. This work advances our limited understanding of MVs in Gram-positive bacteria and reveal a previously unrecognized mechanism underlying S. aureus biofilm formation.

The vaginal microbiome is a critical determinant of womens health. We investigated the genetic basis of common vaginal microbiome species and their biofilm formation. Genomic analysis of Gardnerella vaginalis (Gv) revealed a fundamental phylogenetic split correlating with high- versus low-biofilm phenotypes, driven by clade-specific genomic islands and allelic variants. In a dual-species coculture model of five key vaginal bacteria, Gv achieved numerical dominance, triggering extensive, asymmetric proteomic reprogramming in partner species while showing limited shifts itself. Proteins from biofilm-associated modules showed functional divergence, supported by AI-predicted structural variations in a type II secretion/Tad pilus system, which is first discovered from Gv strains. Integrated metabolomics identified a methyl-{beta}-carboline compound that is elevated in cocultures containing Prevotella bivia (Pb). This compound acts as a potent and selective inhibitor of Gv and Pb biofilms, sparing Lactobacillus crispatus. This work establishes a direct genomic basis for Gv virulence and demonstrates how interspecies interactions govern community dynamics and antimicrobial metabolite production. HighlightsO_LIComprehensive genomic resource comparing with high-quality long-read whole genomes and reference Gardnerella vaginalis and Lactobacillus iners strains. C_LIO_LIIntegrated multi-omics and functional analysis on the most common vaginal microbiome species using 16S rRNA gene sequencing, proteomics, metabolomics, and in vitro assays. C_LIO_LIKey phenotypes quantified, including biofilm formation and polymicrobial interactions. C_LIO_LIConserved Type II Secretion/Tad Pilus System identified across all Gardnerella vaginalis strains, with AI-predicted structural modeling. C_LIO_LIEvaluation of growth inhibition using metabolites against a panel of relevant microbes, including vaginal microbes and opportunistic pathogens. C_LI

Mucosal barriers serve as a multifunctional interface and nutrient-rich habitat for diverse microbes, including bacteria and bacteriophages. Some phages can bind to mucin glycoproteins via carbohydrate-interacting modules and provide an additional layer of mucosal immunity by shielding the underlying epithelium from invading bacteria. However, the role of mucins in shaping phage-bacterium interactions remains poorly understood. We investigated the dynamics between highly pathogenic Yersinia enterocolitica serotype O:8 and its mucus-adherent phage fMtkYen801 under in vitro mucosal environment. We assessed how mucin supplementation, varying phage doses, nutrient and temperature conditions influence phage-bacterium dynamics and biofilm formation. We found that pre-exposure to mucins led to enhanced phage replication in the bacterial host, with a 2-log increase in phage titers, and high abundance of surviving bacteria. Interestingly, mucin glycoproteins also provided Y. enterocolitica a nutrient source and a chemical cue to modulate its growth and biofilm biogenesis. Genomic analysis of phage-resistant bacterial variants revealed mutations in virulence, quorum sensing, and antibiotic resistance genes in both mucin enrichment and control groups, suggesting potential fitness tradeoffs during resistance evolution. Collectively, these findings highlight the importance of mucosal surfaces as an important ecological driver of phage-host interactions in Y. enterocolitica, a significant enteric pathogen, and emphasize the need for investigating these dynamics under complex, physiologically relevant systems to inform better phage therapy strategies against mucosal bacterial infections.

Unicellular microorganisms can make a transition to multicellular states that enhance survival under environmental fluctuations. In bacteria, one of these states is the biofilm, defined by the production of an extracellular matrix. Although biofilm maturation and dispersion have been extensively studied, where and how initial matrix production is induced within a growing population remains largely unknown. Here we show that production of colanic acid, an important matrix component, is initiated around topological defects, where cell orientation mismatches and growth-induced pressure builds up, in bacterial monolayers. Using Escherichia coli reporting mechanically induced production of colanic acid in response to cell contact and deformation, we found matrix production accompanied by out-of-plane growth under agar-pad confinement. Controlling confinement geometry using microfluidic devices dictated the positions of topological defects and thereby localized regions of high matrix production. These findings reveal that the cell orientation patterning spatially organizes mechanical cues to induce matrix production for biofilm initiation of bacteria.

Red, dry and rough (rdar) biofilm formation in Escherichia coli is characterized by the coordinated production of extracellular cellulose and amyloid curli fimbriae. Although rdar biofilm formation has been extensively characterized in laboratory strains, its clinical relevance and implications for antimicrobial treatment remain poorly understood. Here, we systematically investigate rdar biofilm formation of 150 consecutively isolated E. coli strains recovered from patients with urinary tract infections and correlate it to antimicrobial resistance. Genetic analysis of rdar regulation revealed distinct nucleotide signatures within the csgD promoter region that discriminate semi-constitutive rdar expression from temperature-dependent phenotypes, highlighting regulatory plasticity among clinical isolates. Whole-genome sequencing-based phylogenetic analysis further demonstrated that rdar-positive isolates are distributed across diverse E. coli phylogroups and sequence types, indicating that rdar biofilm formation is not restricted to specific clonal lineages. Strikingly, phenotypic assays revealed that the fluoroquinolone antibiotic ciprofloxacin suppresses rdar biofilm formation and associated extracellular matrix architecture in ciprofloxacin-resistant isolates at subinhibitory concentrations, suggesting that ciprofloxacin modulates biofilm-associated pathways beyond its canonical bactericidal targets. Together, our findings establish the rdar morphotype as a clinically relevant biofilm phenotype in uropathogenic E. coli and reveal an antibiofilm activity of ciprofloxacin that is uncoupled from antibiotic resistance. These results underscore the importance of considering antibiotic-mediated modulation of biofilm behavior when interpreting treatment responses and designing strategies to combat persistent urinary tract infections.

Listeria monocytogenes is a foodborne pathogen of utmost interest to food industry stakeholders because it persists in food processing environments. The ability to form biofilms - bacterial communities of autoaggregated cells embedded in a self-produced matrix - contributes to its persistence. While it is known that biofilm cells exhibit different gene expression than their planktonic counterparts, it remains to be elucidated whether those differences persist once cells detach from the biofilm and what their implications might be for food safety. Therefore, this study examines the differential sigB expression in biofilm-derived cells from three L. monocytogenes strains isolated from the environment within a food model subjected to varying osmotic stress over a 15-day storage period. Under our experimental conditions, biofilm-derived L. monocytogenes cells showed higher sigB expression compared to planktonic counterparts. The upregulation was strain-dependent and transient, suggesting that physiological memory may influence stress adaptation during early storage but dissipates over time. Then, the safety implications of sigB upregulation in biofilm-derived cells were assessed by evaluating cell survival under a simulated gastric environment (pH 1-3). The biofilm-derived cells showed a significant increase in survival under severe gastric conditions compared to the planktonic counterparts. Overall, our findings highlight the need to consider biofilm-derived cells in shelf-life studies and predictive models to more accurately reflect real contamination scenarios. Relying exclusively on planktonic cultures introduces a bias that may compromise risk analysis and decision-making.

In a healthy host, the residential microbes help regulate the growth of pathobionts, which are common members of the human gut microbiome, preventing them from causing diseases, including infections, under certain conditions. In cases of dysbiosis, this protection may be compromised. Targeted microbiome modulation offers a promising approach to restore healthy conditions in a disrupted community and consequently prevent infections using the natural colonization resistance of the microbiome. Elucidating the interaction mechanisms between microbial species within a microbiome is crucial for understanding how a microbiome can be modulated precisely and effectively to benefit the hosts well-being. Here, we investigated the interactions between the pathobiont C. perfringens and human gut commensals on physiological and molecular levels. We found that commensal strains affect C. perfringens growth by competing for substrates such as amino acids or a carbon source other than glucose. We further observed that Bacteroidaceae strains altered the levels of C. perfringens proteins, among others, the host-directed {theta}-toxin. Our findings reinforce the notion that modulating the composition of the gut microbiome is an effective strategy to prevent infections.

The incidence of colorectal cancer (CRC) has been increasing in Taiwan and is associated with multiple risk factors, including aging, obesity, and dietary habits. Increasing evidence suggests that gut microbiota dysbiosis contributes to CRC development. This study aimed to characterize microbial and metabolic alterations across premalignant and malignant colorectal lesions and to identify potential microbiome-associated biomarkers. Individuals undergoing colonoscopy for screening or surveillance at Taipei Veterans General Hospital were enrolled. Gut microbial composition was analyzed using full-length 16S rRNA gene sequencing to achieve high-resolution taxonomic profiling. Predicted functional pathways were inferred from microbial communities, and targeted metabolomic profiling was performed to evaluate microbial metabolic outputs. A total of 122 individuals were included, comprising 62 healthy controls, 15 adenoma cases, and 45 CRC cases. Progressive shifts in microbial composition and predicted functional pathways were observed along the adenoma-carcinoma sequence. Several bacterial taxa, including Phocaeicola dorei, Anaerotignum faecicola, Negativibacillus massiliensis, and Dysosmobacter segnis, were enriched in CRC. At the functional level, CRC samples showed enrichment of pathways associated with energy metabolism and bacterial stress responses. Metabolomic analysis further revealed increased levels of tauro-ursocholanic acid in CRC samples, whereas short-chain fatty acids (SCFAs) were reduced compared with controls. Integrative analysis combining full-length 16S sequencing, functional pathway prediction, and metabolomic profiling revealed coordinated microbial and metabolic alterations across the adenoma-carcinoma sequence. These findings provide insight into microbiome-associated processes in colorectal tumorigenesis and suggest potential microbial and metabolic biomarkers for CRC. ImportanceColorectal cancer (CRC) develops through a adenoma-carcinoma sequence, yet the microbial and metabolic alterations accompanying this progression remain incompletely understood. In this study, we integrated full-length 16S rRNA gene sequencing with metabolomic profiling to characterize taxonomic, functional, and metabolic changes across healthy controls, adenoma, and CRC. Our results reveal synchronized shifts in specific microbial taxa, predicted metabolic pathways, and fecal metabolites along the adenoma-carcinoma sequence. Several bacterial species, including Phocaeicola dorei, Anaerotignum faecicola, and Dysosmobacter segnis, increased in CRC, whereas short-chain fatty acids decreased progressively from controls to adenoma and CRC. Functional pathway analysis further indicated alterations in microbial fermentation, amino acid metabolism, and energy-related pathways. Together, these findings highlight the potential role of microbiome-associated metabolic changes in colorectal tumorigenesis and suggest candidate microbial and metabolic markers that may aid in understanding disease development and improving risk stratification.

The surface of fresh vegetable leaves harbors diverse microorganisms with the potential to influence human health through the microbiome-food-gut axis. We investigated the ecology of the bacterial and fungal microbiota on green and red lettuces (n=143) for a 12-month period using high-throughput amplicon sequencing, and assessed the potential transfer of these microbiota to the human gut. Lettuce-associated fungal and bacterial microbiota exhibited substantial temporal variation, converging into two distinct seasonal cycles: early-season (S1) and late-season (S2). Seasonal progression from S1 to S2 increased species richness in season-specific fungal and bacterial taxa, while inducing abundance shifts in persistent fungal taxa and compositional shifts in persistent bacterial taxa. These seasonal dynamics resulted in more complex and stable microbial networks, in which potentially pathogenic fungi were less frequently enriched. Comparative analyses with gut microbiota datasets from 2,831 (fungal) and 3,254 (bacterial) individuals revealed that lettuce-associated fungi and bacteria were widely detected in the human gut, with bacteria detected more frequently than fungi. Season-specific taxa were detected more frequently than persistent taxa, and microbial assembly in the gut was shaped by both neutral and deterministic processes. Notably, lettuce-associated bacteria predominantly co-occurred with non-plant glycan-degrading commensal bacteria in a season-dependent manner, and enrichment of these co-occurring taxa correlated positively with gut microbiota richness and composition. Our findings provide insights into the ecological linkages between fresh vegetable microbiota and the human gut microbiota through the food-gut axis.

Trichomonas vaginalis is an extracellular parasite that inhabits the human genital tract, yet little is known about how it senses and responds to the complex vaginal microbial ecosystem. Here, we show that T. vaginalis exhibits chemotactic behavior on semisolid surfaces, forming multicellular assemblies that coordinate collective migration. Parasite colonies display both positive and negative chemotactic responses, indicating the ability to detect and react to diffusible signals. Different parasite strains display marked mutual avoidance between neighboring colonies, highlighting specific recognition mechanisms. Furthermore, we show that T. vaginalis is strongly attracted to acidic environments, revealing a niche-adapted pH taxis. Given that vaginal bacteria critically shape local pH, we examined parasite responses to representative members of the vaginal microbiota. T. vaginalis exhibited preferential chemotactic migration toward Lactobacillus gasseri, a hallmark species of eubiotic community state types (CSTs), over Gardnerella vaginalis, which is associated with dysbiotic CST-IV communities, while showing no detectable attraction to Escherichia coli. This selective migration correlated with a robust chemotactic response to lactic acid, a major metabolite produced by lactobacilli. Additionally, when the parasite is co-cultured with the equal number of L. gasseri and G. vaginalis, T. vaginalis exhibits a clear preferential binding to L. gasseri, as demonstrated by flow cytometry and fluorescent microscopy. We show that co-culture of T. vaginalis with either L. gasseri or G. vaginalis results in enhanced parasite growth only in the presence of L. gasseri. Collectively, these findings reveal pH taxis; bacteria-directed migration and preferential association with Lactobacillus as previously underappreciated behavioral traits of T. vaginalis. Such behaviors may destabilize protective microbial communities and drive the transition toward a CST-IV-type dysbiotic state which is frequently associated with trichomoniasis.