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FEMS Microbiology Ecology

Oxford University Press (OUP)

Preprints posted in the last 7 days, ranked by how well they match FEMS Microbiology Ecology's content profile, based on 54 papers previously published here. The average preprint has a 0.04% match score for this journal, so anything above that is already an above-average fit.

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Genome-resolved insights into microbial diversity and elemental cycling in Winogradsky columns

Anthopoulos, S. P.; Boutwell, K. P.; Deans, G. T.; Glinski, M. J.; Zhong, Z.; Byambasuren, K.; Miskelly, A. J.; Shrestha, P.; Braden, B.; Faivre-Nigro, R.; Feliu, K.; Garlock, E.; Hotaling, A. G.; Kanaovicz, M. G.; Manning, B. E.; McGill, K.; Phoenix, S.; Ryu, D.; Solfrian, J. L.; Rodriguez-Bornot, C. A.; Yang, J.; Goff, J. L.

2026-08-30 microbiology 10.64898/2026.08.29.748020 medRxiv
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Winogradsky columns are a classic model ecosystem for studying microbial biogeochemistry across steep gradients of oxygen and sulfide. They also remain widely used in microbiology education, introducing generations of students to microbial diversity. Yet, the genomic potential of their microbial communities remains uncharacterized. Here, we applied shotgun metagenomic sequencing to a Winogradsky column community at multiple depths, yielding 20 metagenome-assembled genomes (MAGs) representing diverse, largely uncultivated taxa. Genome-resolved analyses revealed metabolically diverse oxygenic and anoxygenic phototrophs that could potentially contribute to carbon and nitrogen fixation across all layers of the column. Most of these phototrophs also encoded one or more pathways for sulfur oxidation, which we speculated may support both energy conservation and/or sulfide detoxification by these populations. Complex carbon degradation capacity was also widespread across the MAGs, suggestive of the potential for the transformation of the column's amended organic matter (shredded coffee filters) into smaller depolymerization products and, through fermentation, organic acids. Together, these findings reveal how distinct microbial guilds might partition interconnected carbon, sulfur, and nitrogen transformations within redox-stratified systems.

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Osmotic adaptation rather than stress response: A time-resolved proteomic analysis of PEG-induced water limitation in Phytophthora cinnamomi

Vinson, L. S.; Loo, T.; Kulshreshtha, S.; Dobson, R. C. J.; Meisrimler, C.

2026-08-31 microbiology 10.64898/2026.08.30.747438 medRxiv
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Water availability is critical for plants and their microbial communities, including pathogens. The plant pathogen Phytophthora cinnamomi persists in soils with fluctuating moisture, yet cellular responses to water limitation remain poorly understood in Phytophthora and oomycetes more broadly. Although we recently characterized the proteomic response of P. cinnamomi to NaCl-induced osmotic and ionic stress, its response to PEG-mediated water limitation remains poorly understood, leaving a critical gap in our understanding of drought-relevant stress adaptation. Here, we quantified mycelial growth and profiled time-resolved proteome dynamics of P. cinnamomi during polyethylene glycol (PEG-3350)-treatment, simulating moderate water limiting conditions. Treatment with 5% PEG-3350 enhanced radial mycelial growth relative to controls, with no early growth inhibition observed. Label-free proteomics identified 1,097 protein groups, with 880 proteins shared between conditions and an asymmetric abundance profile dominated by decreasing protein abundance over time. Only a small subset of proteins increased, mainly enzymes involved in redox buffering (e.g., thioredoxin and glutaredoxin-like proteins) and mitochondrial/metabolic regulation (e.g., alternative oxidase) and mitochondrial/metabolic regulation. Hierarchical clustering revealed a potential three-phase temporal program: early translational and regulatory remodeling (1-6 HPT), sustained metabolic adjustment (6-12 HPT), and delayed engagement of redox and proteostasis functions (12-24 HPT). Network analysis demonstrated that redox-associated function was integrated throughout this adaptation, with individual clusters further specialized by cofactor preference (NADP- versus NAD-dependent enzymes) and distinct metabolic roles (malate dehydrogenase, CoA-ligase activity). This coordinated, multi-phase reorganization sustained mycelial growth despite moderate osmotic stress, indicating that P. cinnamomi employs active proteomic adaptation rather than passive stress tolerance. These findings reveal the cellular mechanisms underlying drought persistence in this invasive pathogen and suggest molecular targets for disease management under water-limited conditions.

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Red and blue light cues drive contrasting remodeling of lipophilic metabolites and photophysiology in natural benthic diatom biofilms

Desparmet, A.; Lavaud, J.; Jesus, B.; Medico, A.; Hubas, C.

2026-09-01 cell biology 10.64898/2026.08.30.748109 medRxiv
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Intertidal mudflats are low hydrodynamic energy environments hosting microphytobenthic communities that experience strong spatiotemporal variability in light regimes, including changes in spectral quality and light intensity that can lead to cellular photooxidative stress. To cope with these fluctuations, autotrophs exhibit diverse and highly plastic adaptations that are often species-dependent and shaped by their ecological niches. This study investigates photophysiological responses and metabolic remodeling in a diatom assemblage originating from a natural winter microphytobenthic biofilm under contrasting red and blue light intensities. To this end, photosynthetic parameters were monitored alongside changes in lipophilic metabolites, including untargeted lipids and lipophilic pigments. While few metabolites showed temporal remodeling, rapid and contrasting changes were observed within 30 minutes in response to both spectral quality and light intensity. Red light treatments induced broader remodeling of lipophilic metabolites than blue light, whereas blue light appeared to have a greater impact on photosynthetic parameters. Moreover, red light induced xanthophyll-cycle responses comparable to those observed under blue light at equivalent incident intensity. We discuss these metabolic responses in relation to diatom photoadaptive strategies, placing these findings within the intertidal environmental framework. This work further underlines the importance of understanding rapid metabolic plasticity in coping with light fluctuations, providing new insights into the photoregulatory strategies of natural microphytobenthic communities.

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Soil Microbial and Biochemical Properties under Conservation Agriculture in rice-based cropping systems in lower Indo-Gangetic Plain of West Bengal

Singh, P.; Jaison, M.; Saha, N.; Dutta, S.; Sen, A.; Biswas, T.; Mandal, B.; Mukherjee, S.; Dash, B.; Sahu, B.; Patel, R.; Dasgupta, A.

2026-08-31 microbiology 10.64898/2026.08.31.748290 medRxiv
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Microbial and biochemical properties of soil respond quickly with management practices, than chemical and physical properties. Moreover, impact of conservation agriculture (CA) on soil microbial properties is limited to microbial enumeration, but its effect on soil enzyme and microbial activity is little documented. To address these problems soil enzyme activities [dehydrogenase (DHA), {beta}-glucosidase (BGA), acid phosphatase (AcP) and alkaline phosphatase (AlP) and fluoresceine diacetate (FDA)], microbial activites ((Nitrogen fixation (NFBAct), Phosphate solubilization (PSBAct) & Cellulolytic activities (CDBAct)), microbial biomass ((Soil microbial biomass carbon (SMBC) & soil microbial biomass nitrogen (SMBN)) and available nutrient were studied to evaluate biological soil health in alluvial soil of lower Indo-Gangetic plain (IGP) under CA. Field experiment was conducted in split plot design (SPD), under 3 cropping systems (RMCp: rice-maize-cowpea; RWGg: rice-wheat- green gram; RCfBr; rice-cauliflower- bororice/summer rice). Tillage operations (CT: conventional; MT: minimum and ZT: zero tillage) was main plot and residue application as sub plot treatments [(R0 (no residue), R50 (50% residue) and R100 (100% residue)], treatments were replicated thrice. Biological soil health index (BSHI) indicated that among different degree of CA, ZT (0.464) and (MT=0.441) and R100 (0.464) treatment showed better response. Among different cropping system RMCp (0.359) & RWGg (0.343) outperformed RCfBr (0.609) cropping system with respect to (wrt) microbial and biochemical properties of the soil. Results indicated that for restoring microbial and biochemical properties of soil CA can be used as sustainable practice to restore agro-ecosystem. Keywords: Conservation agriculture, Cropping systems, Soil enzyme, Soil microbial properties, Residue application, Tillage operations.

5
Warm temperature impedes the spread of a heritable manipulative symbiont community in spider populations

White, J. R.; Robinson, J. D.; Doremus, M. R.

2026-09-01 ecology 10.64898/2026.08.31.747884 medRxiv
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Heritable bacterial symbionts are pervasive in terrestrial arthropods, often imposing reproductive manipulations to promote their own spread within host populations. Co-infections are common, potentially allowing symbiont co-infectors to hitchhike through a host population. However, adverse thermal conditions can disrupt these communities, particularly when co-infectors vary in their thermal sensitivity. We used a multi-generation experiment to test whether warm (29 {degrees}C) conditions disrupted spread of heritable symbionts through uninfected populations of the spider, Mermessus fradeorum. We tested two common infection combinations: a single infection with a cytoplasmic incompatibility (CI) inducing Rickettsiella or a feminizing co-infection that included a feminizing Wolbachia, the same Rickettsiella, and up to three apparent hitchhikers (two additional Wolbachia strains and Tisiphia). We initiated replicate populations with 1/3 of one infection type and 2/3 uninfected spiders, evaluating population infection rate over 5 spider generations under different temperature regimes. Under cool (21{degrees}C) conditions, Wolbachia feminization drove co-infection to 88% and Rickettsiella CI drove single infection to 83% of host populations. Vertical transmission for all symbionts was high (97-99%) and hitchhiking symbionts also spread effectively. Under warm conditions, feminization and CI efficacy were reduced, and symbionts suffered variably reduced vertical transmission. Warm conditions ultimately destroyed the co-infecting symbiont consortium and impeded symbiont spread. On its own, though, Rickettsiella was still able to increase, despite reduced strength of CI. We hypothesize that contrasting tensions between feminizing spread of the symbiont consortium versus environmentally driven loss of function and transmission may explain observed patterns of mixed infections in field populations of this spider.

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EcoEnamel: Development of a Gelatin-Pectin Film for S. mutans Inhibition and Enamel Preservation in an In Vitro Model

Merle, J. A.; Javelona, G.

2026-09-01 microbiology 10.64898/2026.08.18.745620 medRxiv
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Rinsing-dependent dental hygiene presents a significant public health challenge in water-scarce environments. This study investigated combinations of xylitol (Xyl), chitosan (Chi), glycyrrhizin (Gly), epigallocatechin gallate (EGCG), dicalcium phosphate (DCP), and nano-hydroxyapatite (nHA) on the primary bacteria behind dental caries, S. mutans. These combinations were assessed for markers of dental caries by biofilm reduction, bacterial killing, and acid buffering against S. mutans when applied to an in vitro simulated enamel model using glass bead surfaces for biofilm formation, and gene expression was subsequently examined via RT-qPCR. Separately, mineral retention was also quantified. The EGCG-DCP-Xyl film demonstrated the highest overall efficacy, achieving a significant reduction in biofilm concentration compared to the untreated control and performing similarly in magnitude to the positive toothpaste control. Dead fluorescence staining confirmed that the EGCG-DCP-Xyl film induced the highest rate of non-viable cells, followed by the Chi-Gly film and the Gly-Xyl film. During 10-day pH cycling, the EGCG-DCP-Xyl and DCP-Xyl formulations buffered pH the most, consistently maintaining mean pH levels safely above the demineralization threshold of pH 5.5. The EGCG-DCP-Xyl also optimized mineral stability with the highest retained calcium concentration, significantly outperforming the Chi-Xyl film. At the transcript level, the EGCG-DCP-Xyl film induced substantial downregulation of key virulence genes, yielding decreases in expression for glucosyltransferase B (gtfB), associated with biofilm synthesis, collagen-binding protein (cnm), associated with tissue invasion, and lactate dehydrogenase (ldh), associated with lactic acid production, compared to the untreated control, with effects comparable in magnitude to the positive toothpaste control. This research suggests that targeting bacterial pathways and mineral loss through a portable film may have potential for preventing dental caries, especially in environments where water is limited. However, additional studies are necessary to evaluate real-world effectiveness.

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Constructing microbiome co-occurrence networks with confidence: A conditional, nonparametric, inference-based approach

Song, H.; Xiang, Y.; Liu, H.; Ling, W.; Plantinga, A. M.; Srinivasan, S.; Dun, Y.; Zhao, N.; Sun, S.; Engel, S. M.; Simon, N.; Wu, M. C.

2026-09-01 bioinformatics 10.64898/2026.08.27.747483 medRxiv
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Constructing microbial association networks is a common strategy for exploring relationships among taxa in microbiome studies. Although marginal correlation methods are easy to implement and allow formal inference, they can produce spurious edges driven by indirect associations through other taxa. Conditional graphical-modeling methods aim to recover direct associations, but many rely on Gaussian or linear assumptions and often provide limited uncertainty quantification. We propose a conditional, nonparametric approach based on the scaled expected conditional covariance (SEcov). SEcov measures population-level conditional association by residualizing each taxon with respect to the remaining taxa and scaling the resulting expected conditional covariance. The resulting estimator can incorporate flexible machine-learning methods for conditional-mean estimation and admits asymptotic normal inference, enabling p-values and confidence intervals for taxon-pair associations. We demonstrate through simulation studies that our proposed approach improves network recovery relative to other methods, and we illustrate the new method via construction of a co-occurrence network for the vaginal microbiome during pregnancy. IMPORTANCEHigh-throughput sequencing has made it possible to characterize microbial communities at large scale, and network analysis is widely used to summarize relationships among taxa. However, networks based on marginal correlations may include indirect associations, whereas many conditional graphical models rely on assumptions that may be difficult to justify for sparse, zero-inflated, compositional microbiome data. SEcov offers a practical alternative by estimating conditional associations nonparametrically and attaching inferential uncertainty to individual edges. This allows investigators to construct microbiome networks using statistically interpretable evidence for taxon-pair associations, rather than relying solely on arbitrary correlation cutoffs or regularization tuning parameters.

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Rapid isothermal amplification of diatom rbcL from eDNA and eRNA reveals their abundance and photosynthetic physiology

Verret, F. G.; Hartle-Mougiou, K.; Chantzaras, C.; Peltekis, A.; Margiotta, F.; Sarno, D.; Cardini, U.; Alba, M.; Pizziol, V.; Markopoulos, I.; Papadopoulou, I.; Percopo, I.; Tramontano, F.; Maselli, M.; Novellino, A.; Psarra, S.; Montresor, M.; Mowlem, M. C.; Gizeli, E.; Valiadi, M.

2026-08-31 microbiology 10.64898/2026.08.30.748096 medRxiv
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Diatoms are major contributors to marine primary production, yet current approaches for monitoring their abundance and function rely on coarse satellite chlorophyll estimates or sparse cell count and carbon fixation measurements. Molecular markers are a promising approach for high-resolution measurement of both abundance and metabolic activity through analysis of environmental DNA (eDNA) and RNA (eRNA). We present an isothermal quantitative recombinase polymerase amplification (qRPA) assay targeting rbcL gene copies and transcripts of marine diatoms, operating at low temperature and producing results in less than 15 min. We demonstrate specificity and calibration across diverse diatom taxa, then apply the assay to eDNA and eRNA samples from the Mare Chiara Long-Term Ecological Research site in the Bay of Naples, Italy, alongside microscopy, chlorophyll, physicochemical, and carbon-fixation data. Diatom rbcL DNA tracked abundance across five orders of magnitude despite seasonal shifts in community composition. Combining molecular and optical data revealed increased cellular rbcL copies and chlorophyll in low-light winter populations, suggesting enhanced photosynthetic capacity despite lower abundance. Furthermore, rbcL RNA reflected total carbon fixation rates and identified populations with differing carbon fixation activity. These results support rapid, RPA-based rbcL quantification as a robust approach for biomolecular ocean observing.

9
Benchmarking the Intratumoral Microbiome in Pancreatic Ductal Adenocarcinoma: A Longitudinal Assessment of Contamination Sources and Decontamination Strategies

Dang, L.; Eskelson, L.; Hamm, J.; Blumberg, J.; Wegener, U.; Beissbarth, T.; Ellenrieder, V.; Neesse, A.; Ammer-Herrmenau, C.

2026-08-31 cancer biology 10.64898/2026.08.24.746744 medRxiv
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Pancreatic ductal adenocarcinoma (PDAC) harbors a distinct intratumoral microbiome. Yet rigorous characterization of its composition is hampered by pervasive environmental and procedural contamination. Sources of contamination have not been thoroughly explored, and the methods of decontamination have not been sufficiently evaluated in a benchmarking manner. We systematically collected >300 negative control (NCT) samples comprising paraffin from formalin-fixed paraffin-embedded (FFPE) samples, lysis buffer and sterile water over a period of four years processed by different laboratory persons (LP). All samples were sequenced using full-length 16S rRNA gene sequencing with Oxford-Nanopore Technologies. We benchmarked four decontamination methods (restrictive filtering, decontam, SCRuB, and the Nejman et al.-derived (Nj) pipeline) against fresh-frozen tumor samples (FF) from LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre (KPC) mice, using the abovementioned contamination assessment to calculate a composite score for the assessment. Further, we validated those methods via technical replicates. Microbial profiles of NCT samples were significantly determined by control type, LP, year and season reflecting complex batch effects. The 15 most abundant contaminants spanned well-characterized environmental taxa and human commensals from the oral cavity. The LP processing samples left a significant microbial trace highly contributing to the batch effect. Decontamination benchmarking demonstrated that the Nj method consistently outperformed alternatives in both composite score and inter-replicate concordance. Application of Nj to fresh frozen PDAC samples substantially reduced contaminant burden while preserving putative tumor-associated signals in FF but not FFPE samples. Our results support the adoption of the Nj decontamination approach for future intratumoral microbiome studies in fresh frozen tumor samples.

10
Antifungal Resistance and Adhesin-Mediated Phenotypic Plasticity Among Genomically Diverse Candida auris Clinical Isolates

Wang, T.; Ma, T.; Zhou, C.; Gonzalez Martinez, R.; Putnam, N. E.; Johnson, J. K.; Jabra-Rizk, M. A.

2026-08-31 microbiology 10.64898/2026.08.26.747207 medRxiv
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Candida auris (currently Candidozyma auris) is an emerging fungal pathogen responsible for dramatic global increase in invasive candidiasis with high mortality. Most concerning, C. auris has a high propensity to colonize patients and persist and develop multidrug resistance to main classes of antifungals. In this study, we investigated the genetic and phenotypic diversity and resistance mechanisms of C. auris clinical isolates recovered from hospitalized infected patients. A total of 53 isolates from 38 unique patients were recovered from various clinical sources and evaluated for susceptibility to routine antifungal drugs. Whole genome sequencing (WGS) and single nucleotide polymorphism (SNP) analysis were performed to generate a phylogenetic network to infer population structure and identify mutations associated with drug resistance development. Isolates were also phenotypically evaluated for ability to form biofilms and aggregate, and cell wall adhesins gene expression studies were performed to provide mechanistic insights into C. auris phenotypic plasticity. Except for one clade III isolate, all isolates belonged to clade I and all were resistant to fluconazole with incidence of resistance to amphotericin B, echinocandins or both. Non-synonymous SNPs were found in genes associated with antifungal resistance including ERG11, TAC1B, CDR1 and FKS1. Phenotypically, isolates varied in their ability to form biofilm and aggregate which correlated with expression of the Scf1 and Als4112 cell wall adhesins genes highlighting C. auris phenotypic plasticity in circulating clinical strains. These findings underscore the growing clinical threat posed by C. auris and reinforce the need for optimized surveillance and treatment strategies for controlling its spread.

11
Differential Biofilm Susceptibility and Potent Isavuconazole Post-Antifungal Effect Distinguish Cutaneotrichosporon dermatis from Trichosporon asahii

Yoshinouchi, T.; Nakamura, T.; Mori, D.; Yasunaga, J.-i.; Tanaka, Y.

2026-08-31 microbiology 10.64898/2026.08.30.748177 medRxiv
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Cutaneotrichosporon dermatis (formerly Trichosporon dermatis) is a basidiomycetous yeast-like fungus known to cause summer-type hypersensitivity pneumonitis, although its virulence in humans remains poorly understood. We performed morphological and molecular identification of an isolate from the sputum and blood cultures of an immunocompromised patient, together with pathogenicity assessment using a Galleria mellonella model, biofilm formation/eradication assays, antifungal susceptibility testing, drug combination effects, and the post-antifungal effect (PAFE), compared with Trichosporon asahii. The isolate was identified as C. dermatis by ITS/IGS1 sequencing, supported by phylogenetic analysis. Growth of C. dermatis increased more at 37 than at 25. In the Galleria mellonella assay, C. dermatis, T. asahii, and Candida albicans each showed dose-dependent pathogenicity at sufficiently high inocula, although Rhizopus oryzae was the most potent pathogen on a per-CFU basis. C. dermatis formed biofilms that were more completely inhibited by terbinafine (TRB) and amphotericin B (AmB) than azole agents, which showed only partial inhibitory activity even at high concentrations. Susceptibility testing showed relatively strong susceptibility to AmB and azole agents. In the TRB and azole combination assay, the fractional inhibitory concentration index (FICI) was below 0.5, indicating synergy. Isavuconazole (ISC) showed a markedly stronger PAFE than the other azole agents tested. These findings indicate that although azoles show only partial efficacy against its biofilm, C. dermatis can still cause invasive infection, and that azole monotherapy or TRB and azole combination therapy, aided by the potent PAFE of ISC, may represent effective treatment options.

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Patterns and Drivers of Diatom Diversity and Biogeography in the North Pacific

Barral, A.; Suzuki, K.; Kikuchi, Y.; Nakaoka, S.-i.; Takao, S.; Nakaoka, S.

2026-08-31 ecology 10.64898/2026.08.30.746603 medRxiv
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Marine diatoms contribute to about 20% of global primary production. We present the first basin-scale, multiyear assessment of diatom communities in the North Pacific, combining taxonomically high-resolution RuBisCO large subunit gene (rbcL) metabarcoding with concurrent environmental measurements. Using a nine-year time series of daily samples resolved at the species level via ~500 bp rbcL fragments, we performed multivariate analyses across biogeographic provinces, identifying significant correlations between community structure and environmental drivers such as temperature and macronutrient availability. We report the prevalence of a previously overlooked centric diatom species in the North Pacific, Eunotogramma lunatum, which appears to be near-dominant even in subarctic high-nitrate, low-chlorophyll waters where pennate diatoms are typically favored. These results demonstrate the power of rbcL for large-scale ocean monitoring and provide a critical baseline for future studies of diatom population dynamics, climate change impacts, and ecosystem resilience in a key marine region.

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Persistence of Extended Spectrum β-Lactamase-Producing Enterobacterales in the Gut Microbiome of Healthy Newborns

Shuai, W.; Mithal, L. B.; Kremer, A.; Aron, A.; Sajwani, A.; Huntinghouse, D.; Hartmann, E. M.; Arshad, M.

2026-09-03 infectious diseases 10.64898/2026.09.01.26361559 medRxiv
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The global prevalence of Extended-spectrum {beta}-lactamase-producing Enterobacterales (ESBL-E) colonization is increasing. However, it is unclear whether ESBL-E persist and if that is associated with an altered gut microbial ecology especially in early life where the developing microbiome may not provide the same colonization resistance as in adults. In this study, we collected longitudinal infant gut microbiome samples at delivery and in the nonclinical home setting in Chicago, Illinois, U.S.A, aiming to disentangle how genetic factors pertaining to the ESBL-E, as well as the surrounding gut ecology, influences persistence in the infant gut microbiome. We observed not only a higher-than-expected prevalence of ESBL-E in healthy infant gut microbiomes, but also a trend of ESBL-E persistence once colonized. Microbial communities showed higher dissimilarity between ESBL-E positive and negative infant gut microbiome at earlier time points. Although dissimilarity decreased over time, we present evidence that ESBL-E persist even when traditional detection methods are negative.

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Loss of replication and transcription systems accompanying transition to nucleus-dependent replication in Ariadnavirales, a proposed new order in nucleocytoviricot class Megaviricetes

Yutin, N.; Wolf, Y. I.; Krupovic, M.; Koonin, E. V.

2026-08-30 evolutionary biology 10.64898/2026.08.29.747986 medRxiv
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Sicyoidochytrium minutum DNA virus (SmDNAV) was isolated several years ago from a protist host of family Thraustochytriaceae of the class Labyrinthulomycetes. This virus shared little similarity to other viruses in gene content and protein sequences, albeit seemingly belonging to the phylum Nucleocytoviricota. By extensive searches in genomic and metagenomic sequence databases, we identified numerous long contigs related to the SmDNAV genome and analyzed proteins shared by these putative viruses. Phylogenetic analyses place these viruses within the class Megaviricetes, outside of all established orders, and as a sister group to the clade combining families Mamonoviridae and Manesviridae. Homologs of SmDNAV proteins were found in association (either integrated or co-sequenced) with other Labyrinthulomycetes and Rhodophyta protists from diverse marine and freshwater environments. Consequently, we propose SmDNAV as the prototype member of a new order, provisionally named Ariadnavirales, within class Megaviricetes, phylum Nucleocytoviricota. Members of Ariadnavirales have lost most of the genes encoding components of the replication and transcription systems that are otherwise conserved in nucleocytoviricots, suggestive of transition to genome replication and expression dependent on the host nucleus.

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Combined production of Non-Hemolytic Enterotoxin and Sphingomyelinase as a marker of diarrheal food poisoning strains in the Bacillus cereus group

de Freitas Cardoso, P.; Gilois, N.; Trinidade Vilas-Boas, G.; Lereclus, D.; Gohar, M.; Perchat, S.; Slamti, L.

2026-08-31 microbiology 10.64898/2026.08.27.747690 medRxiv
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The Bacillus cereus group comprises bacteria of biotechnological interest, but also raises health concerns. Some bacteria in this group are opportunistic human pathogens, mainly causing foodborne gastrointestinal infections. As of today, the presence, sequence variability, or expression of genes encoding toxins or other virulence factors are insufficient to predict the potential of a given isolate to cause the diarrheal form of the disease. To address this limitation, we developed a sandwich ELISA to quantify the NheA and Sphingomyelinase (SMase) proteins in culture supernatants to test them as markers of pathogenic potential. Application of the assay to a collection of B. cereus group isolates revealed that strains associated with food poisoning outbreaks produce significantly more NheA and SMase than those isolated from the environment or from commercial products. Statistical analyses show that the combined quantification of NheA and SMase provides robust discrimination between pathogenic and non-pathogenic (environmental and commercial) profiles. These results demonstrate that the quantitative assessment of both NheA and SMase production can serve as a reliable biomarker for distinguishing diarrheic food poisoning isolates from harmless strains.

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Discovering 25 novel phyla that fill gaps in the eukaryotic tree of life

Tedersoo, L.; Mikryukov, V.; Sildever, S.; Chmolowska, D.; Piwosz, K.; Meyneng, M.; Monjot, A.; del Campo, J.; Lara, E.; Hakimzadeh, A.; Geisen, S.; Panksep, K.; Bahram, M.; Oliverio, A.; Shepherd, R.; Rückert, S.; Lanzen, A.; Hurdeal, V.; Concetta Eliso, M.; Casotti, R.; Hosseynimoghadam, M.; Siano, R.; Chauvet, M.; Prins, V.; Kisand, V.; Anslan, S.; Alkahtani, S.; Nilsson, H.

2026-08-31 microbiology 10.64898/2026.08.28.747736 medRxiv
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Protists play important roles in food chains and symbioses in soil and aquatic environments, displaying an enormous morphological and functional diversity. While most commonly found protist species are well known to science, our global-scale environmental DNA survey across soil, water, and sediments reveals dozens of novel, phylum-level phylogenetic lineages that remain to be characterized for basic morphology and function. A vast majority of these undescribed taxa occur in marine water and sediments, but some are common in soil. Most of these novel taxa have distinct substrate and habitat preferences and biogeographic patterns. To accord these lineages scientific agency and enable unambiguous scientific communication, we propose formal names for 150 species to phylum-level taxa from 25 deep lineages based on eDNA and rRNA gene long-read sequence information.

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AmPair: automating housekeeping-gene primer design for species-level metataxonomics

Xu, X.; Yang, X.

2026-09-01 bioinformatics 10.64898/2026.08.25.746527 medRxiv
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Amplicon sequencing of the 16S rRNA gene is the most widely used approach for profiling bacterial communities, but its taxonomic resolution is typically limited to the genus level. Many species carry multiple divergent 16S rRNA alleles that overlap across species boundaries, an ambiguity that even full-length, long-read sequencing cannot fully resolve. Shotgun metagenomics achieves species-level resolution but remains costly, particularly when only a single genus is of interest. Amplicon sequencing of rapidly evolving, protein-coding housekeeping genes offers a cost-effective alternative, yet no tool exists to identify suitable primer sets for a given target taxon. Here we present AmPair, a Snakemake pipeline that, given a target genus and one or more candidate housekeeping genes, designs and ranks primer pairs binding conserved regions while flanking a variable region capable of species-level discrimination, and validates them in silico across all available genomes. Using the genus Bacillus and the housekeeping gene tuf as a case study, the primer set recommended by AmPair amplified 99% of 2,392 genomes; only 0.04% carried multiple alleles and none showed inter-species allele overlap, compared with 91.41% and 69.49%, respectively, for the standard 16S rRNA V1-V9 region. Applied to a Bacillus community profiled by Nanopore sequencing, the same primers resolved closely related species. AmPair thus offers a generalizable and accessible route to species-level community profiling.

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Two methylthio-alkane reductases are functionally distinct in the purple nonsulfur bacterium Rhodopseudomonas palustris

Marquez Reyes, N. L.; Arroyo-Carriedo, A. A.; North, J. A.; Fixen, K. R.

2026-08-31 microbiology 10.64898/2026.08.20.746119 medRxiv
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Organosulfur compounds are the predominant sulfur source in terrestrial environments, requiring bacteria to use enzymes for their assimilation. Most described organosulfur-assimilating enzymes require oxygen, and enzymes that function under anoxic conditions remain poorly understood. Recently, methylthio-alkane reductase (Mar), a nitrogenase-like enzyme that reduces the volatile organic sulfur compounds (VOSCs) methylthio ethanol (MT-EtOH), dimethyl sulfide (DMS), and ethyl methyl sulfide (EMS) under anoxic conditions, was identified in the purple nonsulfur bacterium Rhodospirillum rubrum. However, another purple nonsulfur bacterium, Rhodopseudomonas palustris, has three loci of nitrogen fixation-like (NFL) genes with high sequence similarity to Mar, suggesting additional Mar-like enzymes with distinct roles. Here, we tested whether these NFL genes are required for VOSC assimilation in R. palustris. RNA-seq analysis revealed that all three NFL loci are upregulated under sulfur limitation, supporting a role in sulfur assimilation. Only disruption of the NFL genes encoded by RPA2634-37, renamed marBHDK1, caused fitness defects with EMS, DMS, and dimethylsulfoniopropionate (DMSP) as sulfur sources, indicating a functional Mar enzyme. The NFL genes RPA2347-48 and RPA2353-54, renamed marKD2 and marHB2, were required for activity with MT-EtOH or ethanethiol but not DMS, EMS, or DMSP. No activity was observed for the third locus, RPA2363-64, renamed nflDK. Overall, two Mar homologs in R. palustris are capable of VOSC reduction, one specialized for simple VOSCs and the other preferring a substrate with an additional functional group.

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Effect of Mushroom-Bacteria Co-culture on Mushroom Growth and Antimicrobial Properties

Wang, E.; Cavanaugh, N. T.; He, Y.; Chai, Y.

2026-08-31 microbiology 10.64898/2026.08.30.747672 medRxiv
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Edible mushrooms have been reported to have antimicrobial properties and other health benefits. This study aims to test the antimicrobial activities of several edible mushrooms from markets and test if co-culturing them with bacteria could induce stronger anti-bacterial properties. Commercial mushrooms, Hericium erinaceus (lions mane), Pleurotus ostreatus (oyster mushroom), Lentinula edodes (Shiitake) and Agaricus bisporus (button mushroom), were grown from strictly controlled/sterile substrates. Ethanol and water extracts from the mushrooms were prepared and tested against the bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis, and the fungus Candida albicans for antimicrobial activities. Shiitake water extract (SWE) showed strong antibacterial effects against all tested bacterial species, inhibitory effects on their biofilms, and antifungal activity. The antimicrobials in SWE seem to damage the cell wall and cell membrane of the bacteria, prefer weak acidic conditions, and are heat labile. Some antimicrobials are likely proteins and polysaccharides. In contrast, 3 other mushrooms displayed only weak antimicrobial effects. The fast-growing lions mane and oyster mushroom were co-cultured with different bacteria. The co-cultivation promoted the fruiting body development of lions mane. Co-culturing with S. aureus increased the anti-bacterial effects of lions mane against S. aureus, E. coli and particularly B. subtilis. Co-culturing the oyster mushroom with bacteria, especially B. subtilis and P. aeruginosa, boosted the mushroom growth. All tested bacteria, especially S. aureus, increased oyster mushroom anti-bacterial effect against E. coli and B. subtilis. The findings indicate that mushroom-bacteria co-culturing could have benefits both agriculturally and medicinally.

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Wastewater Surveillance of Oncogenic Viruses: A Baseline Assessment in Southeast Queensland, Australia

Keller, R.; Gebrewold, M.; Smith, W.; Verhagen, R.; Simpson, S.; Hoar, C.; Healy, H. G.; Ahmed, W.

2026-09-04 epidemiology 10.64898/2026.09.02.26362014 medRxiv
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Wastewater surveillance (WS) offers a non-invasive means of tracking population-level circulation of infectious agents, including viruses linked to cancer. This study provides the first Australian assessment of oncogenic viruses in municipal wastewater by screening 76 influent samples collected over four months from six wastewater treatment plants in Southeast Queensland, Australia. Ten gene targets representing seven oncogenic viruses including Epstein-Barr virus (EBV), hepatitis B virus (HBV), hepatitis C virus (HCV), human herpesvirus 8 (HHV-8), human papillomavirus 16 and 18 (HPV-16 and -18), human T-lymphotropic virus type 1 (HTLV-1), and Merkel cell polyomavirus (MCPyV) were analysed using PCR-based methods. All viruses were detected in wastewater at least once, though with substantial variation in frequency. MCPyV was the most frequently detected virus, appearing in 97.3% of samples with concentrations ranging from 3.09-3.85 log10 gene copies (GC)/50 mL, indicating widespread population exposure. HBV (26.3%) and EBV (15.8%) were detected intermittently across multiple catchments, while HPV-16/18, HHV-8, HTLV-1, and HCV were detected at the lowest frequencies (<8%). This study reports the first baseline dataset for oncogenic viruses in Australian wastewater. More broadly, positive detection of all targeted oncogenic viruses including those associated with low prevalence infections in wastewater demonstrates the potential of WS to complement existing cancer surveillance systems in tracking community-level circulation of these infectious agents.