Biology subjects

Schultz, D.

Publications and source records attributed to Schultz, D..

At least 19 recordsLinked to original sources

bioRxiv2026

Ileitis abolishes tolerogenic functions of the enterohepatic bile acid pool

Bile acids (BAs) regulate lipid uptake, epithelial integrity, and immune responses in the gut. Hepatocytes synthesize primary BAs, which microbiota metabolize into secondary metabolites. Together, these species form a composite pool that circulates enterohepatically between the liver and intestines. Here, we show that immunoregulatory outputs of the enterohepatic BA pools involve competition between multiple BA species for individual nuclear receptors and are dependent on intestinal health. In healthy mice, the primary BA, tauro {beta} muricholic acid (t{beta}MCA) antagonized ROR{gamma}t-mediated Th17 function in the presence of two secondary BAs (tDCA, tLCA) which activated ROR{gamma}t. Conversely, ileitis in Crohns disease patients and Tnf{delta}ARE mice depleted primary BAs by reducing the number and function of BA transporting enterocytes. In mice, ileitis driven t{beta}MCA depletion enhanced tDCA and tLCA mediated ROR{gamma}t activation and supported Th17 cell function. Replenishing t{beta}MCA in Tnf{delta}ARE mice reestablished BA dependent Th17 cell regulation. Thus, intra pool competition underpins BA immunoregulatory functions and reveals new opportunities for precision Crohns disease therapy.

immunology↗

bioRxiv2026

Brain Structural and Resting-state Functional Network Changes Following Expiratory Musculature Targeted Resistance Training in Healthy Young Adults: A Pilot Study

Multimodal imaging approaches that combine structural and functional neuroimaging provide a robust framework for examining neuroplastic adaptations that may not be captured by any single modality. The present study investigated the effects of a four-week expiratory muscle strength training (EMST) program on structural and resting-state functional connectivity in healthy young adults. Five healthy young adult males (aged 19-35 years) completed a standard four-week EMST protocol and underwent pre- and post-training imaging assessments. Structural neuroimaging included T1-weighted and diffusion-weighted MRI, which were analyzed using voxel-based morphometry, surface-based morphometry, and white-matter structural connectivity. Functional neuroimaging consisted of resting-state fMRI to assess training-related changes in functional architecture, network connectivity, and global network measures. Structural MRI analyses revealed no significant changes in gray or white matter volume, cortical morphology, or white-matter structural connectivity following EMST (all FWE- or FDR-corrected p > .05). In contrast, resting-state fMRI demonstrated a significant increase in whole-brain functional connectivity (FDR-corrected p = .036), accompanied by greater network integration, reflected in increased local efficiency and transitivity and reduced modularity. Network-level analyses showed enhanced within- and between-network connectivity in sensorimotor and cognitive circuits. Our findings demonstrate robust functional reorganization following EMST, despite the absence of detectable macrostructural or large-scale white-matter connectivity changes, at least within the timescale and sample characteristics of the current study. These results reflect early-stage neuroplasticity, both globally and within the networks underlying speech and swallowing control and suggest that functional reorganization occurs early in training and likely precedes longer-term structural modifications in these networks.

neuroscience↗

bioRxiv2026

Within-host population structure, migration, and parallel adaptive evolution of Pseudomonas aeruginosa in cystic fibrosis lung disease

Pseudomonas aeruginosa infections in adults with cystic fibrosis (CF) are comprised of heterogeneous populations, most often tracing ancestry back to a single recent common ancestor. What is not clear is the physical spatial structure within the lung infection population, its stability over time and whether this physical structure leads to different evolutionary trajectories in different adaptive environments. To compare the P. aeruginosa populations across a single lung, we performed whole genome sequence analyses of 450 isolates recovered from lavage samples of the three different lobes of the right lung from a person with mild-to-moderate CF lung disease at three time points over the course of [~]1.5 years. We found that isolates fell into five distinct phylogenetic lineages with evidence for repeated translocation of isolates from different lineages across lobes and loss-of-function mutations in lasR and mucA were present in all 450 isolates. The well-resolved phylogenetic analyses revealed a structured population in which we find the coexistence of a slowly evolving lineage and more rapidly evolving lineages. There is also support for numerous migration events. Further, strong evidence for parallel adaptive mutations in multiple genes revealed distinct evolutionary paths affecting mucoid phenotypes and genetic variation in antibiotic resistance-associated pathways across coexisting populations within a single individual over time. These results provide an example of within-host evolution leading to microheterogeneity that may be useful to consider in future study of infection metapopulations dynamics over the course of chronic infection. IMPORTANCEIndividuals with cystic fibrosis (CF) commonly have chronic lung infections that contain clonally derived Pseudomonas aeruginosa populations with genotypic and phenotypic diversity. This study describes a substantial dataset containing 450 isolates from different lobes of the right lung across three timepoints from an individual with mild-to-moderate CF lung disease. Some regional enrichment for specific lineages with parallel mutations among individual lobes of the lung was observed, but longitudinal analysis also demonstrated that compartmentalization is not strictly maintained and that isolates migrate between lobes of the lung over time. Perspectives on within lung evolution will be important for understanding the pathogen populations in chronic respiratory infections in CF and other diseases.

microbiology↗

bioRxiv2026

Towards the development of an insulin degradation test

People with diabetes rely on exogenous insulin to reduce blood glucose levels, compensating for insulin resistance or impaired pancreatic {beta}-cell function. Despite being essential for diabetes management, insulin formulations exhibit inconsistent performance due to their relatively fragile stability. This instability carries significant cost implications: some individuals spend over $1,000 USD per month on insulin, and these high prices influence one in six Americans with diabetes to ration their insulin supplies. Environmental stressors can induce conformational changes that cause insulin to misfold and aggregate into fibrils, which are inactive structures that contribute to long-term diabetic complications. Although insulins instability is well-documented, no test currently exists outside of laboratory settings to determine whether an insulin formulation has degraded. Here, we compare biochemical techniques for assessing bioactivity and structural integrity in three commercial insulin analogs exposed to physiologically relevant stress conditions, showing that fibril formation precedes measurable loss of bioactivity in insulin and that fibrillation depends on both the stressor type and the insulin formulation tested. We then demonstrate proof-of-concept testing for antibody-based degradation detection using commercial monoclonal antibody candidates. Together, these findings underscore the critical need for accessible insulin quality testing and demonstrate the feasibility of antibody-based detection of insulin fibrillation. ImportanceInsulin remains one of the most essential yet fragile biopharmaceuticals used in modern medicine. Globally, 150 million people with diabetes depend on exogenous insulin to regulate blood glucose levels, but the proteins inherent instability can cause degradation during storage or transport. These degradation events can reduce insulins potency and safety, yet patients and healthcare providers currently have no practical means to assess insulin quality before injection. This knowledge gap contributes to inconsistent therapeutic outcomes and increases the risk of complications associated with degraded insulin. Our work directly addresses this unmet clinical and public health need by identifying the molecular changes that occur when insulin analogs are exposed to everyday environmental stressors and by completing proof-of-concept testing for a device to detect insulin fibrillation. We demonstrate that structural transitions to fibrils precede measurable loss of bioactivity and that fibrillation behavior depends on both the insulin analog and the stressor type. By combining biochemical characterization with antibody-based detection, this study establishes a foundation for a low-cost, accessible method to verify insulin integrity outside the laboratory. Such a tool could prevent the use of degraded insulin, improve treatment consistency, and empower patients to ensure the quality of their medication. More broadly, this approach exemplifies how protein stability monitoring can be integrated into biotherapeutic quality assurance, improving safety, efficacy, and trust in life-sustaining biologic medicines.

biochemistry↗

bioRxiv2026

Antibiotic exposure dynamically generates a substantial number of heterogeneous persisters along a spectrum of tolerance

Antibiotics are known to induce new persister cells during treatment, yet the inability to distinguish and quantify pre-existing versus drug-induced persisters has long obscured how antibiotics and genes shape persistence. Here, we develop a quantitative framework integrating kinetic modeling with serial-dilution time-kill (SDTK) assays to resolve persister population dynamics and accurately quantify both persister types. We show that antibiotic exposure dynamically generates a substantial number of persisters that are heterogeneous and distributed along a persistence spectrum. Across antibiotics, we uncover pronounced differences in rates of persister induction and elimination, with ampicillin inducing persisters at the highest rate and kanamycin at the lowest. Depending on dilution history, drug-induced persisters can dominate the persister pool. Our framework enables identification of genetic determinants specific to pre-existing and/or drug-induced persistence and reveals drug-dependent pre-existing persister fractions. Systematic sequential-drug treatments demonstrate that kanamycin persisters form the most tolerant subset, embedded within ciprofloxacin persisters that in turn are nested within the broader ampicillin persister subpopulation. Together, we propose a Drug-Induced Persistence-Spectrum (DIPS) model in which antibiotics differentially induce and select for persister subsets along a tolerance continuum.

microbiology↗

bioRxiv2025

Core Clock Protein Subcellular Dynamics Coordinate Local and Global Circadian Control in Syncytia.

Circadian rhythms are pervasive among eukaryotes, and the underlying clocks share a common regulatory architecture - a negative feedback loop. A wealth of genetic and biochemical data underpin current perceptions of circadian oscillators but aspects of their cell biology remain cryptic, especially in syncytial systems. We employed novel microfluidic systems and a blind mutant that retains circadian function to simultaneously track multiple clock components in vivo across circadian cycles, revealing remarkable subcellular and subnuclear dynamics of clock proteins and providing insights into spatiotemporal regulation in a multinucleated system. Despite heterogeneity of clock gene (frq) expression, we find robust cycles in FRQ nuclear localization among all nuclei and document free diffusion of multiple clock components among nuclei. Within nuclei, clock components form distinct, small, highly dynamic nuclear bodies that persist throughout the cycle, occasionally co-localizing for circadian regulatory functions. This rich context of in vivo spatiotemporal information illustrates how separate nuclear clocks ensure synchronous regulation of cellular activities across a macroscopic syncytium.

cell biology↗

bioRxiv2025

Slow trajectories generate divergent cell fates following antibiotic stress

Single-cell microfluidic experiments have shown that upon abrupt exposures to antibiotics, genetically homogeneous microbial populations undergo divergent cell fates. The mechanism underlying this divergence is not clear and in particular, the emergence of a range of distinct slow-growing phenotypes cannot be explained by models relying on bistability alone. Here, we propose a model for gene expression and growth dynamics during antibiotic exposures, which is informed by well-known scaling relations connecting proteome allocation and cell growth. In our model, resources available for transcription and translation of resistance genes act like generalized momenta and their initial variation is predictive of cell fate. Our model reproduces key experimental observations, including the prediction of specific phenotypes and a critical threshold in initial resource allocation that predicts cell survival. These results offer an alternative mechanism for the emergence of phenotypic diversity where slow cell growth effectively stabilizes cellular states along the trajectory that are far from the final stable states predicted by fixed points.

microbiology↗

bioRxiv2025

Gastrointestinal delivery of mRNA lipid nanoparticles selectively targets the pancreas

Lipid nanoparticles (LNPs) administered parenterally often show poor localization to the gastrointestinal (GI) tract and pancreas. In addition, patients typically prefer orally administered drugs to those given intravenously. We therefore investigated whether GI delivery, achievable via device mediated microneedle injections applied to buccal, gastric, small intestinal, colonic, or rectal tissues, could simultaneously enhance LNP delivery to the GI and pancreas while avoiding intravenous administration. Using a combined approach of formulation optimization and GI delivery site screening, we found that cationic SM-102 LNPs delivered gastrically achieved 7-fold higher pancreas delivery in rodents than intravenous neutral SM-102 LNPs. With dose optimization, gastric LNPs achieved 6000-fold greater pancreas to liver targeting ratios than intravenous LNPs. These results suggest GI microneedle administration can reprogram LNP biodistribution, thereby expanding therapeutic opportunities for both local and systemic nucleic acid delivery.

bioengineering↗

bioRxiv2024

Common regulatory mutation increases single-cell survival to antibiotic exposures in Pseudomonas aeruginosa.

Typical antibiotic susceptibility testing (AST) of microbial samples is performed in homogeneous cultures in batch environments, which does not account for the highly heterogeneous and dynamic nature of antibiotic responses. The most common mutation found in P. aeruginosa lineages evolved during chronic infections in the human lung, a loss of function of repressor MexZ, increases basal levels of multidrug efflux MexXY, but does not increase resistance by traditional minimal inhibitory concentration (MIC) assays. Here, we use single cell microfluidics to show that P. aeruginosa response to aminoglycosides is highly heterogeneous, with only a subpopulation of cells surviving exposure. In contrast, strains carrying mexZ mutations bypass the lengthy process of MexXY activation, increasing survival to sudden drug exposures and conferring a fitness advantage in fluctuating environments. Building on the data we present here, we propose a simple "Response Dynamics" assay to quantify the rate of population-level recovery to drug exposures across strains. We used this assay to profile a representative panel of 49 P. aeruginosa strains from diverse environments, showing that the presence of mexZ mutations correlates with faster population recovery from exposures to aminoglycosides, and thus confers an advantage to cells exposed to a sudden, large dose of antibiotic. We propose that the Response Dynamics assay can be used alongside MIC assays for profiling of antibiotic sensitivity to better predict clinical outcomes from in vitro sensitivity/resistance profiles. SignificanceCommon mutations affecting the regulation of antibiotic resistance in bacterial pathogens often do not increase resistance by traditional measures. However, antibiotic resistance is typically measured in stable cultures, without accounting for fluctuations in drug concentration. Here, we show that P. aeruginosa response to aminoglycosides is highly heterogeneous, and that the most common mutation found in clinical isolates improves resistance by increasing single-cell survival to drug exposures. Therefore, the success of antibiotic treatments depends on the dynamics of drug delivery and the heterogeneous activation of microbial responses. We then develop an assay to measure resistance in a dynamic context, which captures this overlooked aspect of antibiotic resistance and can be used alongside traditional measures in the profiling of clinical isolates.

microbiology↗

bioRxiv2024

Quantifying forms and functions of intestinal bile acid pools in mice

Bile acids (BAs) are gastrointestinal metabolites that serve dual functions in lipid absorption and cell signaling. BAs circulate actively between the liver and distal small intestine (i.e., ileum), yet the dynamics through which complex BA pools are absorbed in the ileum and interact with intestinal cells in vivo remain ill-defined. Through multi-site sampling of nearly 100 BA species in individual wild type mice, as well as mice lacking the ileal BA transporter, Asbt/Slc10a2, we calculate the ileal BA pool in fasting C57BL/6J mice to be [~]0.3 moles/g. Asbt-mediated transport accounts for [~]80% of this pool and amplifies size, whereas passive absorption explains the remaining [~]20%, and generates diversity. Accordingly, ileal BA pools in mice lacking Asbt are [~]5-fold smaller than in wild type controls, enriched in secondary BA species normally found in the colon, and elicit unique transcriptional responses in cultured ileal explants. This work quantitatively defines ileal BA pools in mice and reveals how BA dysmetabolism can impinge on intestinal physiology.

physiology↗

bioRxiv2023

Short-term evolution of antibiotic responses in highly dynamic environments favors loss of regulation

To adjust to sudden shifts in conditions, microbes possess regulated genetic mechanisms that sense environmental challenges and induce the appropriate responses. The initial evolution of microbes in new environments is thought to be driven by regulatory mutations, but it is not clear how this evolution is affected by how quickly conditions change (i.e. dynamics). Here, we perform experimental evolution on continuous cultures of tetracycline resistant E. coli in different dynamical regimens of drug administration. We find that cultures evolved under gradually increasing drug concentrations acquire fine-tuning mutations adapting an alternative efflux pump to tetracycline. However, cultures that are instead periodically exposed to large drug doses evolve transposon insertions resulting in loss of regulation of the main mechanism of tetracycline resistance. A mathematical model shows that sudden drug exposures overwhelm regulated responses, which cannot induce resistance fast enough. These results help explain the frequent loss of regulation of resistance in clinical pathogens.

microbiology↗

bioRxiv2023

Dispersal of a dominant competitor can drive multispecies coexistence in biofilms

Despite competition for both space and nutrients, bacterial species often coexist within structured, surface-attached communities termed biofilms. While these communities play important, widespread roles in ecosystems and are agents of human infection, understanding how multiple bacterial species assemble to form these communities and what physical processes underpin the composition of multispecies biofilms remains an active area of research. Using a model three-species community composed of P. aeruginosa, E. coli, and E. faecalis, we show with cellular scale resolution that biased dispersal of the dominant community member, P. aeruginosa, prevents competitive exclusion from occurring, leading to coexistence of the three species. A P. aeruginosa bqsS deletion mutant no longer undergoes periodic mass dispersal, leading to local competitive exclusion of E. coli. Introducing periodic, asymmetric dispersal behavior into minimal models parameterized by only maximal growth rate and local density supports the intuition that biased dispersal of an otherwise dominant competitor can permit coexistence generally. Colonization experiments show that WT P. aeruginosa is superior at colonizing new areas in comparison to{Delta} bqsS P. aeruginosa, but at the cost of decreased local competitive ability against E. coli and E. faecalis. Overall, our experiments document how one species modulation of a competition-dispersal-colonization trade-off can go on to influence the stability of multispecies coexistence in spatially structured ecosystems.

microbiology↗

bioRxiv2023

Dynamical model of antibiotic responses linking expression of resistance to metabolism explains emergence of heterogeneity during drug exposures

Antibiotic responses in bacteria are highly dynamic and heterogeneous, with sudden exposure of bacterial colonies to high drug doses resulting in the coexistence of recovered and arrested cells. The dynamics of the response is determined by regulatory circuits controlling the expression of resistance genes, which are in turn modulated by the drugs action on cell growth and metabolism. Despite advances in understanding gene regulation at the molecular level, we still lack a framework to describe how feedback mechanisms resulting from the interdependence between expression of resistance and cell metabolism can amplify naturally occurring noise and create heterogeneity at the population level. To understand how this interplay affects cell survival upon exposure, we constructed a mathematical model of the dynamics of antibiotic responses that links metabolism and regulation of gene expression, based on the tetracycline resistance tet operon in E. coli. We use this model to interpret measurements of growth and expression of resistance in microfluidic experiments, both in single cells and in biofilms. We also implemented a stochastic model of the drug response, to show that exposure to high drug levels results in large variations of recovery times and heterogeneity at the population level. We show that stochasticity is important to determine how nutrient quality affects cell survival during exposure to high drug concentrations. A quantitative description of how microbes respond to antibiotics in dynamical environments is crucial to understand population-level behaviors such as biofilms and pathogenesis.

microbiology↗

bioRxiv2023

Community composition and the environment modulate the population dynamics of type VI secretion in human gut bacteria

Understanding the relationship between the composition of the human gut microbiota and the ecological forces shaping it is of high importance as progress towards therapeutic modulation of the microbiota advances. However, given the inaccessibility of the gastrointestinal tract, our knowledge of the biogeographical and ecological relationships between physically interacting taxa has been limited to date. It has been suggested that interbacterial antagonism plays an important role in gut community dynamics, but in practice the conditions under which antagonistic behavior is favored or disfavored by selection in the gut environment are not well known. Here, using phylogenomics of bacterial isolate genomes and analysis of infant and adult fecal metagenomes, we show that the contact-dependent type VI secretion system (T6SS) is repeatedly lost from the genomes of Bacteroides fragilis in adults compare to infants. Although this result implies a significant fitness cost to the T6SS, but we could not identify in vitro conditions under which such a cost manifests. Strikingly, however, experiments in mice illustrated that the B. fragilis T6SS can be favored or disfavored in the gut environment, depending on the strains and species in the surrounding community and their susceptibility to T6SS antagonism. We use a variety of ecological modeling techniques to explore the possible local community structuring conditions that could underlie the results of our larger scale phylogenomic and mouse gut experimental approaches. The models illustrate robustly that the pattern of local community structuring in space can modulate the extent of interactions between T6SS-producing, sensitive, and resistant bacteria, which in turn control the balance of fitness costs and benefits of performing contact-dependent antagonistic behavior. Taken together, our genomic analyses, in vivo studies, and ecological theory point toward new integrative models for interrogating the evolutionary dynamics of type VI secretion and other predominant modes of antagonistic interaction in diverse microbiomes.

microbiology↗

bioRxiv2022

HD-PTP/PTPN23 hypomorphic mice display lipodystrophy

Endosomal Sorting Complexes Required for Transport (ESCRTs) drive reverse topology membrane remodeling events including the formation of intralumenal vesicles within multivesicular bodies, the budding of retroviruses from the plasma membrane, and the scission of the cytokinetic bridge. It has been difficult to study the physiological relevance of this machinery in mammals because many contributing components are essential for viability. To bypass this problem we used combinations of knockout (-), hypomorphic (H) and wildtype (+) alleles to generate a series of mice with a gradual reduction of HD-PTP (product of PTPN23), an ESCRT-associated protein known to cause embryonic lethality when fully depleted. Whereas PTPN23-/H mice died shortly after birth, PTPN23H/H mice developed into adulthood but had reduced size, lipodystrophy, and shortened lifespan. Analysis of 14-day inguinal adipose tissue indicated reduced expression of adipogenesis markers, and PTPN23 knockout preadipocytes similarly display reduced adipogenesis in vitro. Defects in insulin-stimulated signaling were apparent in differentiated PTPN23 knockout adipocytes and PTPN23H/H inguinal adipose tissue in vitro, correlating with reduced levels of insulin signaling hallmarks observed in adult PTPN23H/H inguinal adipose tissue in vivo. Whereas the ESCRT machinery have been suggested to downregulate signaling, these results indicate that HD-PTP promotes insulin-induced signaling in, as well as differentiation of, inguinal adipose tissue. These results revealed unexpected roles for HD-PTP in promoting fat accumulation in mammalian cells through supporting insulin signaling, adipogenesis, and lipid droplet formation.

cell biology↗

bioRxiv2022

Community composition shapes microbial-specific phenotypes in a cystic fibrosis polymicrobial model system

Interspecies interactions can drive the emergence of unexpected microbial phenotypes that are not observed when studying monocultures. The cystic fibrosis (CF) lung consists of a complex environment where particular microbes, living as polymicrobial biofilm-like communities, are associated with negative clinical outcomes for persons with CF (pwCF). However, the current lack of in vitro models integrating the microbial diversity observed in the CF airway hampers our understanding of why polymicrobial communities are recalcitrant to therapy in this disease. Here, integrating computational approaches informed by clinical data, we built a mixed community of clinical relevance to the CF lung composed of Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus sanguinis and Prevotella melaninogenica. We developed and validated this model biofilm community with multiple isolates of these four genera. When challenged with tobramycin, a front-line antimicrobial used to treat pwCF, the microorganisms in the polymicrobial community show altered sensitivity to this antibiotic compared to monospecies biofilms. We observed that wild-type P. aeruginosa is sensitized to tobramycin in a mixed community versus monoculture, and this observation holds across a range of community relative abundances. We also report that LasR loss-of-function, a variant frequently detected in the CF airway, induces tolerance of P. aeruginosa to tobramycin specifically in the mixed community. The molecular basis of this community-specific recalcitrance to tobramycin for the LasR mutant variant is the increased production of redox-active phenazines. Our data support the importance of studying clinically-relevant model polymicrobial biofilms to understand community-specific traits relevant to infections. SIGNIFICANCE STATEMENTThe CF lung is colonized by biofilm-like microbial communities that exhibit both resistance and tolerance (collectively called "recalcitrance") to antimicrobials used in the clinic. Here, we leveraged clinical data from pwCF to inform our understanding of communities exhibiting recalcitrance. We developed and validated an in vitro model that revealed novel, community-specific phenotypes relevant to the clinic. We used this model to explore the underlying mechanism associated with a community-specific emergent behavior. We posit that in vitro models of polymicrobial communities may help in developing new antimicrobial strategies to improve patient outcomes, and that the approach used here can be applied to other polymicrobial models.

microbiology↗

bioRxiv2022

Sulfate reducing bacteria associated to diatoms during a spring phytoplankton bloom

Phytoplankton blooms fuel marine food webs with labile dissolved carbon, but also lead to the formation of particulate organic matter composed of living and dead algal cells. These particles contribute to carbon sequestration, yet are also sites of intense algal-bacterial interactions and provide diverse niches for microbes to thrive. We analyzed 16S and 18S ribosomal RNA gene amplicon sequences obtained from 51 time points and metaproteomes from 3 time points during a spring phytoplankton bloom in the North Sea. Particulate fractions larger than 10 {micro}m diameter were collected at near daily intervals between early March and late May in 2018. Network analysis identified two major modules representing bacteria co-occurring with diatoms and with dinoflagellates, respectively. The diatom network module included known sulfate-reducing Desulfobacterota as well as potentially sulfur-oxidizing Ectothiorhodospiraceae. Metaproteome analyses confirmed presence of key enzymes involved in dissimilatory sulfate reduction, a process known to occur in sinking particles at greater depths. Our results indicate the presence of sufficiently anoxic niches in the particle fraction of an active phytoplankton bloom to sustain sulfate reduction, which may have implications for algal-bacterial interactions and carbon export during blooms.

ecology↗

bioRxiv2022

Influenza A Virus Compromises anti-Streptococcal Innate Immunity

Seasonal influenza epidemics pose a considerable hazard for global health. In the past decades, accumulating evidence revealed that influenza A virus (IAV) renders the host vulnerable to bacterial superinfections which in turn are a major cause for morbidity and mortality. However, whether the impact of influenza on anti-bacterial innate immunity is restricted to the vicinity of the lung or systemically extends to remote sites is underexplored. We therefore sought to investigate intranasal infection of adult C57BL/6J mice with IAV H1N1 in combination with bacteremia elicited by intravenous application of Group A Streptococcus (GAS). Co-infection in vivo was supplemented in vitro by challenging murine bone marrow derived macrophages and exploring gene expression and cytokine secretion. Our results show that viral infection of mice caused mild disease and induced the depletion of CCL2 in the periphery. Influenza preceding GAS infection promoted the occurrence of paw edemas and was accompanied by exacerbated disease scores. In vitro co-infection of macrophages led to significantly elevated expression of TLR2 and CD80 compared to bacterial mono-infection, whereas CD163 and CD206 were downregulated. The GAS-inducible upregulation of inflammatory genes, such as Nos2, as well as the secretion of TNF and IL-1{beta} were notably reduced or even abrogated following co-infection. Our results indicate that IAV primes an innate immune layout that is inadequately equipped for bacterial clearance.

immunology↗