Biology subjects

Mimee, M.

Publications and source records attributed to Mimee, M..

12 recordsLinked to original sources

bioRxiv2026

An engineered Clostridial mini consortium modulates intestinal inflammation

Modern lifestyle factors have altered gut microbiota composition and function. Bacteria in the Clostridia class modulate mucosal immune responses through various mechanisms including production of secondary bile acids (SBA). Here, we present a novel system to study how the SBA isodeoxycholic acid (isoDCA) regulates host immunity. Through targeted mutagenesis of bile acid epimerization genes, we engineered Ruminococcus gnavus to ablate isoDCA production. Combining R. gnavus (WT or KO) with Peptacetobacter hiranonis created a two-member consortium that toggles isoDCA production on or off while keeping all other variables constant. Using this system, we demonstrate that isoDCA induces colonic lamina propria ROR{gamma}t{square} Foxp3{square} regulatory T cells (pTregs) through a mechanism requiring both the Takeda G protein-coupled receptor 5 (TGR5) and the Farnesoid X receptor (FXR). Engraftment of this isoDCA+ consortium protected against colitis in an adoptive T cell transfer model by reshaping the microbiota and suppressing host inflammation.

immunology↗

bioRxiv2026

Programmable genetic control of tumor-colonizing Bifidobacterium longum for intratumoral therapeutic delivery and biocontainment

Engineered bacteria offer a distinct modality for cancer therapy by exploiting the ability of certain species to colonize tumors and deliver therapeutic payloads. Improving their efficacy and safety requires control over bacterial activity after tumor colonization, yet few microbial chassis permit it. Bifidobacterium longum, a probiotic with intrinsic tumor-targeting and antitumor activity, is a promising chassis but lacks such control. Here, we develop a genetic control system that regulates B. longum activity within tumors, from gene expression to bacterial abundance. A human-isolate-derived replicon supports plasmid maintenance without antibiotic selection, and promoter and ribosome-binding-site libraries provide [~]150-fold and [~]48-fold expression ranges, respectively. Signal peptides enable secretion of structurally diverse therapeutic payloads and B. longum secreting CCL21 or an anti-PD-L1 nanobody reduces tumor growth relative to PBS controls. Anhydrotetracycline delivered in drinking water induces transgene expression in tumor-resident bacteria and reduces intratumoral bacterial load through CRISPRi targeting essential genes. Together, these results establish a tumor-homing probiotic as an externally controllable therapeutic chassis.

synthetic biology↗

bioRxiv2026

A comprehensive phage-bacteria interaction atlas links phage lineage and capsule serotype to genome-guided machine learning prediction in Klebsiella pneumoniae

Klebsiella pneumoniae is a WHO critical-priority pathogen for which strain-specific bacteriophages are being explored as precision antimicrobials, yet rapid phage-host matching remains a major barrier to therapeutic deployment. We constructed a comprehensive interaction atlas comprising 84 taxonomically diverse phages and 101 globally sourced, clinically representative K. pneumoniae strains, including multidrug-resistant isolates. Systematic pairwise profiling produced 8,484 interaction measurements, of which 2,656 (31.3%) scored positive for bacterial clearance. Genus was the dominant phage-side determinant of host range, while capsule K-serotype was the strongest host-side determinant of susceptibility; aggregate defense, prophage, plasmid, and antimicrobial-resistance features contributed comparatively little. A genome-guided machine learning model predicted interactions without curated host annotations (AUROC, 0.882; AUPR, 0.765), outperforming a model based only on phage genus and K-serotype and modestly exceeding a curated genomic baseline. The model recovered capsule- and lipopolysaccharide-biosynthesis genes, canonical receptors and defense-associated features as major predictors using SHAP analysis. Feasibility tests of expert- and model-selected cocktails exposed a translational constraint. Although all formulations suppressed growth in vitro, only the specific cocktail whose phages replicated robustly within the murine gut reduced colonization, suggesting in vivo amplification rather than predicted host range as the limiting factor for therapeutic efficacy. Together with the activity of a model-selected cocktail built for an isolate completely excluded from training, these results provide a species-wide resource for K. pneumoniae phage matching and support a hybrid workflow combining genome-based ranking with targeted phenotypic validation.

microbiology↗

bioRxiv2026

Mining Microbial Transcriptomes to Engineer Cell-Based Bacterial Biosensors in Gut-Resident Bacteroidaceae

The gastrointestinal tract is rich in metabolic, immune, and microbiome-derived signals that can inform the design of live biotherapeutics and diagnosis of intestinal disorders. Engineered cell-based biosensors can tap into this molecular information and report on their environment, yet their development in gut-resident symbionts has been limited by a lack of validated sensor systems. Here, we present a generalizable pipeline that leverages bacterial transcriptional profiling to identify environment-responsive systems for biosensor engineering. Candidate Sensors Systems (CSSs) mined from healthy, disease, and in vitro transcriptomes were assembled into a barcoded library in Bacteroidaceae chassis and screened in high-throughput in vivo to identify responsive promoters. A unique Bacteroidales ECF-type sigma factor operon with ties to sphingolipid metabolism and flux was highly responsive in chemically-induced colitis models. The biosensor responded robustly to disease and returned to baseline upon recovery, establishing an in vivo-driven strategy for discovering functional biosensors in non-model gut-resident bacteria.

synthetic biology↗

bioRxiv2026

Microbiome histidine competition mediates dietary control of systemic imidazole propionate

The gut microbiome produces numerous metabolites that influence mammalian health. While microbiome composition and diet influence metabolite concentrations, how these factors interact remains incompletely defined. Here we find production of imidazole propionate (ImP), a microbial metabolite associated with cardiometabolic and neurodegenerative diseases, is determined by the balance of competing metabolic pathways that catabolize histidine to ImP or short-chain fatty acids (SCFAs). We show glutamate serves as a preferred substrate that selectively inhibits histidine conversion to SCFAs, redirecting flux to increased ImP production across mouse- and human-derived microbial communities. We find dietary monosodium glutamate (MSG) acting via this mechanism boosts ImP production in the mouse gut, transiently impairing glucose tolerance and increasing systemic ImP. These findings show that predictable interactions between dietary substrate and microbial competition control systemic ImP levels, providing a mechanistic framework for understanding microbiome metabolite production more broadly.

microbiology↗

bioRxiv2026

Engineered gut symbionts mediate cross-phylum antagonism to suppress uropathogenic Escherichia coli colonization

Urinary tract infections (UTIs) are among the most common bacterial infections globally and create a large burden on the healthcare system. Uropathogenic Escherichia coli (UPEC) account for the majority of UTIs and increase the risk of recurrence. The standard treatment is antibiotics and, with the rise of multi-drug resistant UPEC lineages, there is a need for alternative treatments and prevention. Colicins, bacteriocins targeting and produced by E. coli, have previously been shown to inhibit the growth of pathogenic E. coli and are a promising alternative. Here, we engineer commensal Bacteroidaceae to secrete colicins via outer membrane vesicle (OMV) targeting signal peptides to suppress E. coli in the mouse gut. Secreted colicins were assessed for their ability to kill primary clinical isolate UPEC strains, including epidemic multi-drug resistant ST131 strains, along with other pathogenic and type strains. Specifically, secreted colicin E7, from Phocaeicola vulgatus fully eliminated of several UPEC strains in culture. In mice, P. vulgatus secreting colicin E7 prevented the extended colonization of two clinical UPEC strains and restored microbiome diversity. Together, this work shows the viability of secreted, heterologous antimicrobials from P. vulgatus as prophylactic treatment against the colonization of pathogenic E. coli utilizing cross-phylum antagonism in the gut. Significance StatementRecurrent urinary tract infections can be driven by intestinal reservoirs of uropathogenic Escherichia coli that are difficult to eliminate and increasingly recalcitrant to conventional antibiotic therapy. Here, we show that engineered gut symbionts from the Bacteroidaceae family can secrete targeted protein antibiotics to selectively kill these uropathogenic E. coli. Leveraging outer membrane vesicle-based secretion, we demonstrate that bacteriocin secretion can prevent gut colonization by clinically relevant pathogens, while preserving overall microbiome diversity. This work establishes a strategy for programmable, cross-phylum antimicrobial delivery within the gut microbiome, providing a potential alternative to conventional antibiotics for preventing recurrent infections and other enteric diseases.

synthetic biology↗

bioRxiv2025

Engineering butyrate-producing Lachnospiraceae to treat metabolic disease

Engineering native gut bacteria offers a route to persistent, programmable therapeutics, yet many dominant taxa remain genetically intractable. Lachnospiraceae are a prevalent and abundant family in the human gut microbiome, possessing metabolic functions generally associated with health1. Despite their promise as engineered live biotherapeutics, genetic manipulation of Lachnospiraceae remains challenging. Here, we develop a modular toolkit for Lachnospiraceae engineering, including constitutive and inducible expression and chromosomal integration systems. Applying this toolkit to the native commensal Coprococcus comes, we program secretion of the mammalian cytokine interleukin-22 (IL-22) in the mouse intestinal tract where it elicits ileal transcriptional responses consistent with cytokine signaling. In a mouse model of metabolic associated steatotic liver disease, IL-22-secreting C. comes improves glucose homeostasis and attenuates hepatic steatosis. This work demonstrates that a native Lachnospiraceae chassis can be genetically programmed to modulate host metabolic and immune physiology. The toolkit provides a generalizable foundation for Lachnospiraceae-derived microbiome therapeutics and for probing causal links between Lachnospiraceae gene programs and host phenotypes.

synthetic biology↗

bioRxiv2023

A highly conserved and globally prevalent cryptic plasmid is among the most numerous mobile genetic elements in the human gut

Plasmids are extrachromosomal genetic elements that often encode fitness enhancing features. However, many bacteria carry cryptic plasmids that do not confer clear beneficial functions. We identified one such cryptic plasmid, pBI143, which is ubiquitous across industrialized gut microbiomes, and is 14 times as numerous as crAssphage, currently established as the most abundant genetic element in the human gut. The majority of mutations in pBI143 accumulate in specific positions across thousands of metagenomes, indicating strong purifying selection. pBI143 is monoclonal in most individuals, likely due to the priority effect of the version first acquired, often from ones mother. pBI143 can transfer between Bacteroidales and although it does not appear to impact bacterial host fitness in vivo, can transiently acquire additional genetic content. We identified important practical applications of pBI143, including its use in identifying human fecal contamination and its potential as an inexpensive alternative for detecting human colonic inflammatory states.

microbiology↗

bioRxiv2022

Ingestible capsule for detecting labile inflammatory biomarkers in situ

Transient molecules in the gastrointestinal (GI) tract, such as nitric oxide and hydrogen sulfide, are key signals and mediators of inflammatory bowel disease (IBD). Because these molecules are extremely short-lived in the body, they are difficult to detect. To track these reactive molecules in the GI tract, we have developed a miniaturized device that integrates genetically-engineered probiotic biosensors with a custom-designed photodetector and readout chip. Leveraging the molecular specificity of living sensors, we genetically encoded bacteria to respond to IBD-associated molecules by luminescing. Low-power electronic readout circuits (nanowatt power) integrated into the device convert the light from just 1 L of bacterial culture into a wireless signal. We demonstrate biosensor monitoring in the GI tract of small and large animal models and integration of all components into a sub-1.4 cm3 ingestible form factor capable of supporting wireless communication. The wireless detection of short-lived, disease-associated molecules could support earlier diagnosis of disease than is currently possible, more accurate tracking of disease progression, and more timely communication between patient and their care team supporting remote personalized care.

synthetic biology↗

bioRxiv2021

Cas9-Assisted Biological Containment of a Genetically Engineered Human Commensal Bacterium and Genetic Elements

Sophisticated gene circuits built by synthetic biology can enable bacteria to sense their environment and respond predictably. Biosensing bacteria can potentially probe the human gut microbiome to prevent, diagnose, or treat disease. To provide robust biocontainment for engineered bacteria, we devised a Cas9-assisted auxotrophic biocontainment system combining thymidine auxotrophy, an Engineered Riboregulator (ER) for controlled gene expression, and a CRISPR Device (CD). The CD prevents the engineered bacteria from acquiring thyA via horizontal gene transfer, which would disrupt the biocontainment system, and inhibits the spread of genetic elements by killing bacteria harboring the gene cassette. This system tunably controlled gene expression in the human gut commensal bacterium Bacteroides thetaiotaomicron, prevented escape from thymidine auxotrophy, and blocked transgene dissemination for at least 10 days. These capabilities were validated in vitro and in vivo. This biocontainment system exemplifies a powerful strategy for bringing genetically engineered microorganisms safely into biomedicine.

synthetic biology↗

bioRxiv2020

Antigen-specific induction of CD4+CD8αα+ intraepithelial T lymphocytes byBacteroidetes species

The microbiome contributes to the development and maturation of the immune system1-3 In response to commensal bacteria, CD4+ T cells can differentiate into distinct functional subtypes with regulatory or effector functions along the intestine. Peripherally-induced Foxp3+-regulatory T cells (pTregs) maintain immune homeostasis at the intestinal mucosa by regulating effector T cell responses against dietary antigens and microbes4. Similarly to pTregs, a subset of small intestine intraepithelial lymphocytes CD4+CD8+ (CD4IELS) exhibit regulatory properties and promote tolerance against dietary antigens5. Development of CD4IELS from conventional CD4+ T cells or from Treg precursors depends on the microbiota5,6. However, the identity of the microbial antigens recognized by CD4IELs remains unknown. We identified species belonging to the Bacteroidetes phylum as commensal bacteria capable of generating CD4IEL from naive CD4+ T cells expressing the pTreg transnuclear (TN) monoclonal TCR6 as well as from polyclonal WT T cells. We found that {beta}-hexosaminidase, a widely conserved carbohydrate-metabolizing enzyme in the Bacteroidetes phylum, is recognized by TN T cells, which share their TCR specificity with CD4+ T cells found in the intraepithelial compartment of polyclonal specific-pathogen-free (SPF) mice. In a mouse model of colitis, {beta}-hexosaminidase-specific CD4IELs provided protection from ulceration of the colon and weight loss. Thus, a single T cell clone can recognize a variety of abundant commensal bacteria and elicit a regulatory immune response at the intestinal epithelial surface.

immunology↗

bioRxiv2019

Engineering Phage Host-Range and Suppressing Bacterial Resistance Through Phage Tail Fiber Mutagenesis

The rapid emergence of antibiotic-resistant infections is prompting increased interest in phage-based antimicrobials. However, acquisition of resistance by bacteria is a major issue in the successful development of phage therapies. Through natural evolution and structural modeling, we identified host-range determining regions (HRDR) in the T3 phage tail fiber protein and developed a high-throughput strategy to genetically engineer these regions through site-directed mutagenesis. Inspired by antibody specificity engineering, this approach generates deep functional diversity (>107 different members), while minimizing disruptions to the overall protein structure, resulting in synthetic \"phagebodies\". We showed that mutating HRDRs yields phagebodies with altered host-ranges. Select phagebodies enable long-term suppression of bacterial growth by preventing the appearance of resistance in vitro and are functional in vivo using a mouse skin infection model. We anticipate this approach may facilitate the creation of next-generation antimicrobials that slow resistance development and could be extended to other viral scaffolds for a broad range of applications.\n\nHighlightsO_LIVastly diverse phagebody libraries containing 107 different members were created.\nC_LIO_LIStructure-informed engineering of viral tail fibers efficiently generated host-range alterations.\nC_LIO_LIPhagebodies prevented the development of bacterial resistance across long timescales in vitro and are functional in vivo.\nC_LI

synthetic biology↗