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At least 19 recordsLinked to original sources
PubMed1979

Microbial ecological basis of infant botulism as studied with germfree mice.

The possible role of the indigenous intestinal microflora in the toxicoinfection of human infant botulism was studied with adult germfree mice. Intraintestinal botulinum monoassociation was consistently produced when mice were fed 10 C. botulinum type A spores. Control germfree mice became enterically infected when placed in the same isolator with, but separated from, animals that had been fed spores. When transferred into a room holding a colony of normal mice, the highly susceptible gnotobiotes became resistant to challenge of 10(5) spores after about 3 days of the conventionalizing exposure. The findings are interpreted as evidence that enteric botulinum infection occurs in human infants whose intestinal tract has not yet been colonized by bacteria which are indigenous to adults and prevent growth of C. botulinum. Intestinal monoassociation could not be developed in germfree infant mice younger than 7 days.

Age Factors↗
PubMed2026

Metagenomic Insights Into Microbial Diversity of Tea Rhizosphere of the Kangra Valley.

This study provides the first metagenomic assessment of microbial diversity from the tea rhizosphere of the Kangra valley. Tea rhizosphere soil samples were collected from 4 locations (Dharamshala, Baijnath, Palampur, and Joginder Nagar) of the Kangra valley. DNA extracts of rhizosphere samples were analysed for bacterial and Archaeal diversity using amplicon sequencing (V3-V4) region of the 16S rRNA gene and Fungal diversity using ITS1 and ITS2 regions. Baijnath and Palampur samples showed the highest bacterial richness, while Dharamshala and Palampur had the highest fungal richness. Proteobacteria was a dominant phylum in all the rhizosphere samples, followed by Firmicutes, Actinobacteria, Acidobacteria, and Bacteroidetes. A total of 11 fungal phyla were identified among all the locations, with abundance of Ascomycota and Basidiomycota. For the Archaea domain, uncultured archaeon and Aeropyrum camini were the most common found among all the locations. A small fraction (<&#x2009;0.5%) of Bacillus and Pseudomonas species were observed among all the locations. Alpha and beta diversity indices displayed notable differences within and between microbial diversities. Soil factors were variably associated with microbial diversity, with nitrogen positively aligned with fungal diversity, while EC and K were associated with Archaeal diversity. Soil pH and OM% showed moderate associations with bacterial diversity. These findings provided valuable and comprehensive insights into tea rhizosphere microbial ecology and could be used to better understand microbial functions and their role in plant health.

Rhizosphere↗
PubMed1979

Updated in vivo methods for evaluating topical antimicrobial agents on human skin.

Updated and expanded in vivo quantitative testing procedures to determine the efficacy of topical antimicrobial agents are presented. The occlusion test measures the ability of an agent to prevent the expansion of the resident microflora which occurs when an impermeable dressing is applied to the forearm. Measurements are made at 24 and 48 hr. The expanded flora test measures the ability of an agent to suppress a dense population of micro-organisms produced by expansion of the resident flora of the forearm by prior application of an impermeable occlusive dressing. Measurements are made at 6, 24 and 48 hr or after 10 min in the case for agents designed for immediate degerming. The persistence test measures the ability of an agent to establish a reservoir in skin and exert an antimicrobial effect up to 3 days after the last application of the test material. The ecological shift test determines any major alteration in cutaneous microbial ecology following several applications of the material under occlusive dressings. The serum inactivation test determines whether the presence of serum proteins interferes with antimicrobial activity.

Adult↗
PubMed2025

The ecology and evolution of microbial immune systems: a look on the wild vibrio side.

Natural populations of vibrio beyond the well-studied pandemic strains of Vibrio cholerae, provide a powerful model for investigating the eco-evolutionary dynamics of microbial immune systems. Their genetic diversity, ecological versatility, ease of culturability and the availability of time-series data enable detailed studies of phage-host interactions in natural contexts. This review synthesizes recent advances in vibriophage research, highlighting key findings and emerging tools. High-throughput assays and genomic tools have offered new perspectives on phage specificity, host range and the evolutionary pressures shaping these interactions. Theoretical frameworks, such as arms race and fluctuating selection dynamics, are informed by empirical data from vibrio-phage systems, with time-series sampling providing crucial insights into their temporal and spatial dynamics. A major finding is the role of mobile genetic elements (MGEs) in encoding bacterial defence systems, which shape phage-host coevolution. Discoveries like the phage satellite PICMI illustrate how MGEs facilitate the transfer of antiviral systems, influencing ecological and evolutionary dynamics. The paradox of generalist vibriophages, rare despite their broad host ranges, is also explored. By integrating experimental approaches with field observations, vibriophage research advances microbial ecology and informs sustainable applications in aquaculture and phage therapy, reinforcing vibrios as a versatile model system.This article is part of the discussion meeting issue 'The ecology and evolution of bacterial immune systems'.

Bacteriophages↗
PubMed2026

microntology: a lightweight, data-driven controlled vocabulary to describe earth's microbial habitats.

MOTIVATION: Data-enabled studies of microbial ecology and evolution depend on high-quality descriptions of microbial habitats, based on curated and consolidated vocabularies. RESULTS: We introduce microntology v1.0, a pragmatic controlled vocabulary of 148 terms to describe microbial habitats and lifestyles, and provide manually curated microntology annotations for >300k metagenomic samples from public repositories. AVAILABILITY: microntology controlled vocabulary terms and term hierarchies (doi: 10.5281/zenodo.19730167), and curated annotations for 305 626 metagenomic samples (doi: 10.5281/zenodo.18164252) are available via Zenodo and spire.embl.de/downloads. Underlying code is available via github.com/grp-schmidt/microntology and Zenodo (doi: 10.5281/zenodo.20323497). User feedback, suggestions and bug reports are welcome at github.com/grp-schmidt/microntology/issues.

Ecosystem↗
PubMed2026

Environmental Release of Genetically Intervened Microorganisms: Towards a New Narrative.

The deliberate release of genetically engineered microorganisms for environmental applications has remained largely blocked since the early days of recombinant DNA technology, when limited ecological knowledge, lack of success stories and public apprehension shaped a culture of caution and restrictive regulation. Despite profound advances in microbial ecology, synthetic biology and genetic design, current frameworks still rely on outdated assumptions and legacy regulations that equate engineered microbes with inherent danger and demand unrealistic forms of absolute containment. This review examines how laboratory-trained microorganisms exist on a continuum with naturally evolved life, and that their risks are neither categorically different nor greater. Rather than pursuing unachievable containment, governance should shift towards traceability, stewardship and long-term monitoring through genomic barcodes, digital twins and transparent oversight. The vision moves from domination and control to care and partnership recognizing engineered microbes as live amendments capable of restoring degraded ecosystems. Achieving this transformation requires new terminology, phased field-trial frameworks, improved scaling methods, and the integration of epistemological perspectives that emphasize reciprocity and coexistence with nature. Reframing biotechnology in this way could finally unlock the capacity of engineered microorganisms to contribute responsibly and effectively to planetary repair in an era of escalating environmental crises.

Microorganisms, Genetically-Modified↗
PubMed2026

Global gut microbiome atlas identifies epidemiologic-stage-specific signatures in inflammatory bowel disease.

The global rise of inflammatory bowel disease (IBD) reflects environmental shifts, yet how these changes are embedded in the gut microbial ecology remains unclear. We construct a microbiome atlas comprising 245,627 profiles. By classifying countries into three epidemiologic stages, we establish a framework. As the IBD burden increases, the gut microbial alpha diversity declines, and community structures form distinct clusters. This transition is characterized by a gradient of core genera. Integrating six shotgun metagenomic cohorts, we identify the depletion of anabolic pathways in IBD patients. Strain-level analysis reveals that epidemiologic staging shapes genetic architecture within species, identifying an IBD-enriched subclade of Eisenbergiella associated with elevated fecal cholic acid. We develop a microbial inflammatory risk score (MIRS), based on 19 genera, that discriminates IBD from controls (area under the curve [AUC] = 0.92). MIRS correlates with IBD prevalence. Our study provides an atlas linking epidemiology to microbiome ecology and strain evolution, offering a foundation for population-level surveillance and interventions in IBD.

Humans↗
PubMed2026

Effect of Saccharomyces cerevisiae fermentation postbiotic supplementation on metagenomics of digital dermatitis lesions in lactating Holstein cows.

Digital dermatitis (DD) is the leading cause of lameness in cattle, posing major animal welfare and economic concerns. Effective prevention strategies are increasingly important given emerging antimicrobial resistance associated with common DD treatments. Supplementation with Saccharomyces cerevisiae fermentation postbiotics (SCFP) has been shown to enhance innate immunity and reduce DD lesion development. This study evaluated the effect of a commercial SCFP supplement on the microbial composition of DD lesions using shotgun metagenomic sequencing to characterize microbial communities and associated antimicrobial resistance genes. Beta diversity analysis revealed that stage M4 DD lesions from SCFP-supplemented cows had a trend for different microbial compositions compared with controls (P = 0.051). At the genus level, M2 lesions were found to have statistically significant lower abundance of the genera Desulfovibrio, Pseudomonas, Staphylococcus, Anaerotignum, Caproicibacterium, and Bacteroides in the SCFP treatment group compared with the control (P < 0.05). M2 lesions from the SCFP treatment group were also found to have statistically significant higher abundance of the genera Fusobacterium, Citricoccus, Listeria, and Fundicoccus as compared with the control (P < 0.05). M4 lesions were found to have statistically significant lower abundance of the genera Blautia and Petrimonas in the SCFP treatment group compared with the control (P < 0.05). At the species level, M2 lesions were found to have statistically significant lower abundance of the species Desulfovibrio sp. G11, Anaerotignum sp. MB30-C6, Caproicibacterium argilliputei, and Prevotella intermedia in the SCFP treatment group compared with the control (P < 0.05). M2 lesions from the SCFP treatment group were also found to have statistically significant higher abundance of the species Fundicoccus culcitae and Helcococcus ovis as compared with the control (P < 0.05). Metagenomic analysis identified antimicrobial resistance genes associated with multiple antibiotics commonly used for DD treatment, including tetracyclines, lincosamides, and pleuromutilins. These findings demonstrate the potential for SCFP supplementation to alter the microbial composition of DD lesions while highlighting the ongoing concerns regarding antimicrobial resistance in DD management.IMPORTANCEDigital dermatitis (DD) causes substantial economic loss and welfare concerns in cattle production systems worldwide. Our findings show that dietary supplementation with Saccharomyces cerevisiae fermentation postbiotics (SCFP) has the potential to alter the microbial ecology of DD lesions. Importantly, this work identifies antimicrobial resistance genes within DD lesions, underscoring the limitations of antibiotic-based control strategies. By linking nutritional supplementation to changes in microbial communities and resistance gene profiles, this study advances understanding of non-antibiotic approaches to disease mitigation and supports the development of sustainable, microbiome-informed management practices in food animal production.

Animals↗
PubMed2025

Depth-dependent multi-kingdom microbial interactions and biogeochemical cycling genes in eutrophic shallow lake sediments.

Microorganisms are pivotal to lake ecosystem biogeochemical cycles, yet existing research often focuses on single microbial kingdoms or surface sediments, neglecting multi-kingdom interactions and depth-resolved dynamics. To address these gaps, we used metagenomic sequencing to characterize microbial communities and their functional associations across overlying water and 0-45 cm sediments in four shallow lakes of the middle Yangtze River basin, China. Despite increasing bacterial and fungal diversity with depth, the 0-9 cm surface sediments exhibited the strongest multi-kingdom network connectivity and the greatest microbial stability. Functional genes exhibited clear depth-dependent patterns: nitrogen cycling genes, including those involved in dissimilatory nitrate reduction to ammonium, were most enriched in the upper 0-9 cm of sediment; methane cycling genes were positively correlated with depth; phosphorus cycling genes and some sulfur cycling genes, such as assimilatory sulphate reduction, declined with depth. Sediment microbial assembly was dominated by deterministic processes, in which the vertical distribution of functional genes was primarily dictated by heavy metals and conventional environmental indicators. These findings highlight depth-specific multi-kingdom microbial interactions and their associations with biogeochemical cycling, advancing lacustrine microbial ecology understanding and providing references for lake conservation under environmental change.

Lakes↗
PubMed2026

Detection of opportunistic bacterial pathogens with intrinsic amoxicillin- and cephalosporin-resistance in wild koala faecal microbiomes.

Opportunistic bacterial pathogens frequently associated with human clinical infections, including antimicrobial-resistant strains, are infiltrating the microbiomes of wild animals, where they have the potential to negatively impact wildlife health. Bacterial genes conferring resistance to amoxicillin have previously been reported in koala (Phascolarctos cinereus) faecal DNA. Koalas are facing several key threats, including wildfires, and affected individuals may receive amoxicillin therapy to treat burn wounds. This study aimed to identify the species of amoxicillin-resistant bacteria in koala gut microbiomes and determine if they are opportunistic pathogens. Faecal samples collected from 98 wild-caught koalas were cultured using amoxicillin-supplemented media to isolate amoxicillin-resistant Gram-negative enteric bacteria. Isolates were screened using 16S rRNA PCR and Sanger sequencing to identify opportunistic pathogenic species, which then underwent whole-genome sequencing and antimicrobial susceptibility testing. Intrinsically amoxicillin-resistant opportunistic pathogens were obtained from 9.2% (9/98) of koala faecal samples and comprised Klebsiella oxytoca (6/98, 6.1%), Klebsiella pneumoniae (1/98, 1.0%) and Citrobacter spp. (2/98, 2.0%). Seven of nine amoxicillin-resistant opportunistic pathogens also exhibited cephalosporin resistance. Four K. oxytoca isolates belonged to lineages associated with human clinical infections, which also have the potential to cause disease in koalas, including fatal systemic infections in pouch young. The presence of amoxicillin- and cephalosporin-resistant strains may also increase the risk of gut dysbiosis and opportunistic infections when penicillins or cephalosporins are required to treat bacterial infections in koalas, highlighting the importance of good antimicrobial stewardship. The study findings demonstrate the One Health perspective of microbial pathogens and the intertwined microbial ecology between humans and wildlife.

Animals↗
PubMed2026

Plasmids as persistent genetic reservoirs of bacterial defense systems in wastewater treatment.

BACKGROUND: Bacterial antiphage defense systems play essential roles in microbial ecology, yet their dynamics within urban wastewater systems (UWS) remain poorly characterized. RESULTS: In this study, we performed comprehensive metagenomic and plasmidome analyses on 78 wastewater samples collected during two seasons and four sampling points across UWS from three European countries. We observed a significant reduction in the abundance, diversity, and mobility potential of defense systems during biological treatment. However, these reductions were not directly correlated with changes in microbial abundance. Defense systems were significantly enriched on plasmids, particularly conjugative plasmids, where their gene density was approximately twice as high as on chromosomes and remained relatively stable across compartments. In contrast to chromosomal defense systems, plasmid-borne systems exhibited more frequent co-localization with a wide range of mobile genetic elements (MGEs)-associated genes, thereby facilitating multilayered dissemination networks. Furthermore, we detected a strong correlation between phage abundance and host defense system profiles, indicating ongoing phage-host co-evolutionary dynamics in these environments. CONCLUSIONS: In summary, our results demonstrate that UWS reduce the abundance and diversity of bacterial defense system genes. However, plasmid-associated defense systems can persist through shared mobile genetic reservoirs. These findings underscore the critical role of plasmids in bacterial immunity and provide new insights into defense system dynamics within urban wastewater environments.

Plasmids↗
PubMed2026

Minimizing decompression and warming during deep seawater collection increases abundance and activity of autochthonous bacteria and archaea.

The deep ocean hosts autochthonous pressure-adapted microorganisms that are unique to this environment, as well as allochthonous pressure-sensitive members transported from shallow depths by vertical advection and particle-sinking. However, conventional sampling instruments decompress and warm deep-sea samples during retrieval, potentially altering microbial properties when studied ex situ. Here, we assess this potential sampling bias by comparing seawater microbial communities collected with or without measures aimed at minimizing pressure and temperature effects. When compared to samples collected under pressurized conditions, conventional sampling (using Niskin bottles) was found to affect prokaryotic cells retrieved by reducing their total numbers, diminishing protein synthesis activity (>10%), and also causing overall shifts in the community composition. The most significant compositional change was a >20% decrease in metagenomic archaeal representation (TACK-group/Thaumarchaeota/Nitrososphaerota). Deep-sea bacterial groups had mixed responses to preserving pressure during retrieval, with some groups exhibiting higher representation when samples were maintained pressurized (e.g. members of the family Pelagibacteraceae, unclassified Thiotricales, Thioglobaceae, and Chitinophagaceae), whereas others increased their representation when decompressed (e.g. Burkholderiaceae, Comamonadaceae, and Oxalobacteraceae). This study reveals the existence of bias introduced by the complete decompression of samples retrieved with traditional instrumentation, as well as a decrease in overall bacterial activity when samples are completely decompressed during retrieval. Additionally, incubations lasting for >24&#xa0;h were shown to transform the original prokaryotic community composition. Precautions addressing these effects are necessary to enhance the reliability of ex situ measurements and improve our understanding of deep-sea microbial ecology and biogeochemistry.

Seawater↗
PubMed1979

Evidence by electron micrographs for a high incidence of bacteriophage particles in the waters of Yaquina Bay, oregon: ecological and taxonomical implications.

A variety of viral particles, the majority of them clearly identifiable as bacteriophages, were found in the seawater of Yaquina Bay, Oregon. These phages were obtained as free particles from the seawater without employing specific hosts for enrichments or further purification in the laboratory. A variety of electron micrographs showing different morphologies of phages as well as phage-bacterium interactions found in the seawater are presented. In the area where the bay received organic enrichment from seafood processing plants, a minimum of 10(4) phage particles per ml was estimated. Since the technique used was designed to concentrate particles 0.2 micrometer in diameter or larger it is assumed that the actual number of phage particles is higher than 10(4) particles per ml. The implications of the presence of such phage concentrations in bays and estuaries with a certain level of eutrophication are of obvious importance in considering the microbial ecology of these environments.

Bacteriophages↗
PubMed2026

Field strains of the unicellular alga Chlamydomonas reinhardtii exhibit multicellular characteristics that shape their interactions.

Chlamydomonas reinhardtii is a unicellular green alga long studied as a biological model system but rarely considered from the perspective of its own ecology, thus epitomizing the disconnection between reductionist biology in the laboratory and life in nature. Here, we present insights into its ecology, understood from field strains. We examined bacterial communities that coenriched with C. reinhardtii from the field, revealing specific associations. We then compared the biology of C. reinhardtii field strains to laboratory strains, illuminating strain-level heterogeneity and adaptations to life in the field vs. the laboratory. Field strains exhibited more robust photosynthesis, higher abundances of pherophorin proteins, a propensity for palmelloid formation, and high cell wall permeability. Finally, we phenotyped cocultures of C. reinhardtii with a coenriched bacterial partner, demonstrating how differences between field and laboratory strains manifest in biotic interactions. Although the organisms in question are classically understood as unicellular, our observations of field strains highlighted their participation in multicellular units, challenging the utility of unicellular frameworks in extending our knowledge of model organism biology in the laboratory towards understanding microbial ecology.

Chlamydomonas reinhardtii↗
PubMed2024

A novel Alteromonas phage with tail fiber containing six potential iron-binding domains.

Viruses play a vital role in regulating microbial communities, contributing to biogeochemical cycles of carbon, nitrogen, and essential metals. Alteromonas is widespread and plays an essential role in marine microbial ecology. However, there is limited knowledge about the interactions of Alteromonas and its viruses (alterophages). This study isolated a novel podovirus, vB_AmeP-R22Y (R22Y), which infects Alteromonas marina SW-47 (T). Phylogenetic analysis suggested that R22Y represented a novel viral genus within the Schitoviridae family. R22Y exhibited a broad host range and a relatively large burst size, exerting an important impact on the adaptability and dynamics of host populations. Two auxiliary metabolic genes, encoding Acyl carrier protein and AAA domain-containing protein, were predicted in R22Y, which may potentially assist in host fatty acid metabolism and VB12 biosynthesis, respectively. Remarkably, the prediction of the R22Y tail fiber structure revealed six conserved histidine residues (HxH motifs) that could potentially bind iron ions, suggesting that alterophages may function as organic iron-binding ligands in the marine environment. Our isolation and characterization of R22Y complements the Trojan Horse hypothesis, proposes the possible role of alterophages for marine iron biogeochemical cycling, and provides new insights into phage-host interactions in the iron-limited ocean.IMPORTANCEIron (Fe), as an essential micronutrient, is often a limiting factor for microbial growth in marine ecosystems. The Trojan Horse hypothesis suggests that iron in the phage tail fibers is recognized by the host's siderophore-bound iron receptor, enabling the phage to attach and initiate infection. The potential role of phages as iron-binding ligands has significant implications for oceanic trace metal biogeochemistry. In this study, we isolated a new phage R22Y with the potential to bind iron ions, using Alteromonas, a major siderophore producer, as the host. The tail fiber structure of R22Y exhibits six conserved HxH motifs, suggesting that each phage could potentially bind up to 36 iron ions. R22Y may contribute to colloidal organically complexed dissolved iron in the marine environment. This finding provides further insights into the Trojan Horse hypothesis, suggesting that alterophages may act as natural iron-binding ligands in the marine environment.

Bacteriophages↗