Biology subjects

Steele-Mortimer, O.

Publications and source records attributed to Steele-Mortimer, O..

3 recordsLinked to original sources

bioRxiv2026

Zn2+ as a secondary messenger for exogenous redox potential sensed through Chemosensory Zinc-Binding (CZB) protein domains

Redox environments in nature are shaped by reactive oxygen species (ROS), oxygen availability, and metal ion chemistry, and exert profound effects on cell physiology and survival. While extensive work has characterized how cells resist oxidative damage, the mechanisms by which cells sense and navigate environmental redox conditions remain less well understood. Here, we identify a previously unrecognized and widespread mechanism of redox sensing in Salmonella enterica serovar Typhimurium mediated by the chemosensory zinc-binding (CZB) domain-containing receptor McpA. Using quantitative chemotaxis assays and live-cell imaging, we show that S. Typhimurium exhibits robust, concentration-dependent chemotaxis toward the neutrophil-derived oxidants HOCl and hydroperoxides, with attraction occurring at low, physiologically relevant concentrations below those that cause bactericidal effects, and this response requires McpA and its conserved zinc-binding cysteine. Whereas other Cys-Zn thiolate systems function through direct oxidation mechanisms, we find that the unique 3His,1Cys binding motif of CZBs responds to redox-dependent changes in Zn{superscript 2} speciation, whereby oxidizing conditions shift soluble, bioavailable Zn{superscript 2} into insoluble zinc precipitates. In this way, CZBs utilize the bioavailable Zn{superscript 2} pool as a secondary messenger of exogenous redox potential, and correspondingly, cells exhibit chemoattraction toward Zn{superscript 2}-depleted environments, including sources of ROS, but also toward oxygen-rich conditions that provide a metabolic growth advantage. The broad phylogenetic distribution of CZB domains is consistent with this Zn{superscript 2}-responsive mechanism being an ancient redox-sensing strategy, likely established early in bacterial evolution under changing planetary redox conditions and retained across diverse bacterial lineages. Significance StatementWe report a previously unknown mechanism of redox sensing that operates through changes in the bioavailability and speciation of Zn{superscript 2}, enabling bacteria to detect changes in exogenous redox potential with high sensitivity and navigate redox gradients. The broad phylogenetic distribution of chemosensory zinc-binding (CZB) domains suggests that this zinc-dependent sensory mechanism is an ancient and widespread strategy for detecting environmental redox gradients that arose early in bacterial evolution and may have been subsequently shaped or expanded in response to increasing atmospheric oxygen associated with the Great Oxygenation Event.

microbiology↗

bioRxiv2020

Global mapping of Salmonella enterica-host protein-protein interactions during infection

Intracellular bacterial pathogens inject effector proteins into host cells to hijack diverse cellular processes and promote their survival and proliferation. To systematically map effector-host protein-protein interactions (PPIs) during infection, we generated a library of 32 Salmonella enterica serovar Typhimurium (STm) strains expressing chromosomally encoded affinity-tagged effector proteins, and quantified PPIs in macrophages and epithelial cells by Affinity-Purification Quantitative Mass-Spectrometry. Thereby, we identified 25 previously described and 421 novel effector-host PPIs. While effectors converged on the same host cellular processes, most had multiple targets, which often differed between cell types. Using reciprocal co-immunoprecipitations, we validated 13 out of 22 new PPIs. We then used this host-pathogen physical interactome resource to demonstrate that SseJ and SseL collaborate in redirecting cholesterol to the Salmonella Containing Vacuole (SCV) via NPC1, PipB directly recruits the organelle contact site protein PDZD8 to the SCV, and SteC promotes actin bundling by directly phosphorylating formin-like proteins.

microbiology↗

bioRxiv2019

Highly reproducible murine model of oral Salmonella infection via inoculated food

Oral infection of mice with Salmonella Typhimurium is an important model system. In particular C57Bl/6 mice, which are susceptible to Salmonella, are used to study both systemic and gastrointestinal pathogenesis. Pretreatment with streptomycin disrupts the intestinal microbiota and results in colitis resembling human intestinal Salmonellosis. Oral gavage is typically used for delivery of both antibiotic and bacteria. Although convenient, this method requires a moderate level of expertise, can be stressful for experimental animals, and may lead to unwanted tracheal or systemic introduction of bacteria. Here, we demonstrate a simple method for oral infection of mice using small pieces of regular mouse chow inoculated with a known number of bacteria. Mice readily ate chow pieces containing up to 108 CFU Salmonella, allowing for a wide range of infectious doses. In mice pretreated with streptomycin, infection with inoculated chow resulted in less variability in numbers of bacteria recovered from tissues compared to oral gavage, and highly consistent infections even at doses as low as 103 Salmonella. Mice not treated with streptomycin, as well as resistant Nramp1 reconstituted C57Bl/6J mice, were also readily infected using this method. In summary, we show that foodborne infection of mice by feeding with pieces of chow inoculated with Salmonella results in infection comparable to oral gavage but represents a natural route of infection with fewer side effects and less variability among mice.

microbiology↗