Biology subjects

Hancock, R. E. W.

Publications and source records attributed to Hancock, R. E. W..

11 recordsLinked to original sources

bioRxiv2026

Burkholderia cenocepacia physiology and molecular adaptations to the acidic pH of the CF nutritional environment

Burkholderia cenocepacia is an opportunistic pathogen associated with increased disease severity and mortality in cystic fibrosis (CF) patients. We have previously shown that elevated iron and acidic pH in the CF nutritional environment increases B. cenocepacia growth rate and decreases its susceptibility to some of the antimicrobials used clinically to treat CF infections. Here, we aimed to characterize B. cenocepacia physiology and its molecular response under acidic pH and increased zinc and iron concentrations using a modified synthetic CF sputum media (SCFM-FeZn). By investigating B. cenocepacia internal pH homeostasis, we found that it maintains a neutral internal pH when exposed to mildly acidic media at pH 5.5. We also assessed the effect of B. cenocepacia growth on the pH of SCFM-FeZn. When cultured at pH 6.8, B. cenocepacia maintained a media pH of [~]6.5. In contrast, when the culture pH value was initially 5.5, it increased to 6.5 during growth. Using comparative transcriptomics and metabolomics analysis, we identified 990 differentially expressed genes, and 23 differentially abundant metabolites in supernatants at acidic compared to neutral pH. Some of these genes and metabolites were involved in aromatic amino acid metabolism including the upregulated trpE gene, encoding a tryptophan biosynthetic enzyme. A tryptophan auxotrophic trpE deletion strain grew slower in SCFM-FeZn. Overall, this work identifies mechanisms involved in B. cenocepacia adaptation to acidic pH under conditions to model the CF nutritional environment. Some of these mechanisms are also associated with pathogenicity and virulence. ImportancePathogenic bacteria can be exposed to acidic pH inside and outside the host. Their ability to adapt to pH fluctuations contributes to success in host colonization. B. cenocepacia can grow at acidic pH ([~]3.5) and has been recovered from intracellular acidic compartments of amoebas and macrophages. Adaptation to acidic pH depends on molecular mechanisms that maintain a near optimal pH inside the cell for the function of vital processes. A few mechanisms that contribute to its adaptation to acidic pH have been described, but not in conditions reflecting the CF nutritional environment. Here, we identified multiple differentially-regulated systems that are associated with bacterial susceptibility to antimicrobials and pathogenesis. This research provides a better understanding of the role of acidic pH on B. cenocepacia physiology in the CF nutritional context and highlights possible systems that should be further characterized.

microbiology↗

bioRxiv2025

Time-course Transcriptomics Reveals the Impact of Treponema pallidum on Microvascular Endothelial Cell Function and Phenotype

Syphilis, caused by Treponema pallidum subsp. pallidum, is an urgent global public health threat. Syphilis vaccine development has been impeded by limited understanding of the molecular mechanisms that enable T. pallidum to establish and maintain infection. The vascular endothelium is critical for T. pallidum attachment, dissemination, and host immune response initiation; however, the molecular details of T. pallidum-endothelial interactions are incompletely understood. To enhance understanding, we performed time-course transcriptomic profiling on T. pallidum-exposed brain microvascular endothelial cells. These analyses showed T. pallidum exposure altered pathways related to extracellular matrix, growth factors, integrins, and Rho GTPases. The induced transcriptional response was consistent with endothelial to mesenchymal transition, a process involved in fetal development and vascular dysfunction. This study provides a comprehensive understanding of the molecular responses of endothelial cells to T. pallidum and identified the host pathways that might cause syphilis disease symptoms, information that could aid in syphilis vaccine design. Highlights{square} Exposure of microvascular endothelial cells to Treponema pallidum subsp. Pallidum significantly alters the endothelial cell transcriptome {square}Signaling pathways related to extracellular matrix organization, growth factors, integrins, and Rho GTPases were overrepresented for genes differentially expressed in T. pallidum-exposed endothelial cells {square}Exposure to T. pallidum induces pathways and factors consistent with endothelial to mesenchymal transition, a host process central to development that may explain the devastating effects of congenital infection {square}T. pallidum exposure induces expression of Snail, the main transcription factor associated with the process of endothelial to mesenchymal transition O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/651946v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@e121beorg.highwire.dtl.DTLVardef@6e4caeorg.highwire.dtl.DTLVardef@16c3f03org.highwire.dtl.DTLVardef@19cf020_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

The Use of DeepQSAR Models for The Discovery of Peptides with Enhanced Antimicrobial and Antibiofilm Potential.

Withdrawal StatementThe authors have withdrawn this manuscript because issues discovered in the dataset required removal of certain external peptides and a recalculation of performance metrics. Revised analyses will be presented separately. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

bioinformatics↗

bioRxiv2024

Design of highly potent anti-biofilm, antimicrobial peptides using explainable artificial intelligence

Antimicrobial peptides have emerged as a potential alternative to traditional small molecule antibiotics. They possess broad-spectrum efficacy and increasingly confront the challenges of bacterial resistance, especially the adaptive resistance of biofilms. However, advanced rational peptide design methods are still required to ensure optimal property profiles of such peptides, while limiting the cost of their synthesis and screening. Here we present a computational pipeline for the rational de novo design of antimicrobial and anti-biofilm peptides based on an explainable artificial intelligence (XAI) framework. The developed framework combines a Wasserstein Autoencoder (WAE) and a non-linear dimensionality reduction method termed generative topographic mapping (GTM). The WAE was used to learn the latent representation of the peptide space, while the GTM guided the generation of novel AMPs through an illustrative depiction of the latent space in the form of 2D maps. The efficacy of the peptides generated with the developed pipeline was experimentally verified by synthesis and testing for activity against methicillin resistant Staphylococcus aureus (MRSA), achieving a 100% hit rate in targeting biofilms. Notably, the most potent anti-biofilm peptide developed in this study demonstrated almost one order of magnitude improvement in IC50 value compared with the potent anti-biofilm peptide reference "1018", used as a positive control. The developed pipeline is readily extendable for the optimization of additional peptide properties, including cytotoxicity, tendency to aggregate and proteolytic stability, underscoring its potential utility for rational design of the peptide-based therapeutics.

bioinformatics↗

bioRxiv2024

Intracellular Pseudomonas aeruginosa persist and evade antibiotic treatment in a wound infection model

Persistent bacterial infections evade host immunity and resist antibiotic treatments through various mechanisms that are difficult to evaluate in a living host. Pseudomonas aeruginosa is a main cause of chronic infections in patients with cystic fibrosis (CF) and wounds. Here, by immersing wounded zebrafish embryos in a suspension of P. aeruginosa isolates from CF patients, we established a model of persistent infection that mimics a murine chronic skin infection model. Live and electron microscopy revealed persisting aggregated P. aeruginosa inside zebrafish cells, including macrophages, at unprecedented resolution. Persistent P. aeruginosa exhibited adaptive resistance to several antibiotics, host cell permeable drugs being the most efficient. Moreover, persistent bacteria could be partly re-sensitized to antibiotics upon addition of anti-biofilm molecules that dispersed the bacterial aggregates in vivo. Collectively, this study demonstrates that an intracellular location protects P. aeruginosa in vivo from host innate immunity and antibiotics, and provides new insights into efficient treatments against chronic infections.

microbiology↗

bioRxiv2023

Dynamic gene expression analysis reveals distinct severity phases of immune and cellular dysregulation in COVID-19

BackgroundCOVID-19 patients experience dynamic changes in immune and cellular function over time with potential clinical implications. However, there is insufficient research investigating, on a gene expression level, the mechanisms that become activated or suppressed over time as patients deteriorate or recover, which can inform use of repurposed and novel drugs as therapies. ObjectiveTo investigate longitudinal changes in gene expression profiles throughout the COVID-19 disease timeline. MethodsThree-hundred whole blood samples from 128 adult patients were collected during hospitalization from COVID-19, with up to five samples per patient. Transcriptome sequencing (RNA-Seq), differential gene expression analysis and pathway enrichment was performed. Drug-gene set enrichment analysis was used to identify FDA-approved medications that could inhibit critical genes and proteins at each disease phase. Prognostic gene-expression signatures were generated using machine learning to distinguish 3 disease stages. ResultsSamples were longitudinally grouped by clinical criteria and gene expression into six disease phases: Mild, Moderate, Severe, Critical, Recovery, and Discharge. Distinct mechanisms with differing trajectories during COVID-19 hospitalization were apparent. Antiviral responses peaked early in COVID-19, while heme metabolism pathways became active much later during disease. Adaptive immune dysfunction, inflammation, and metabolic derangements were most pronounced during phases with higher disease severity, while hemostatic abnormalities were elevated early and persisted throughout the disease course. Drug-gene set enrichment analysis predicted repurposed medications for potential use, including platelet inhibitors in early disease, antidiabetic medications for patients with increased disease severity, and dasatinib throughout the disease course. Disease phases could be categorized using specific gene signatures for prognosis and treatment selection. Disease phases were also highly correlated to previously developed sepsis endotypes, indicating that severity and disease timing were significant contributors to heterogeneity observed in sepsis and COVID-19. ConclusionsHigher temporal resolution of longitudinal mechanisms in COVID-19 revealed multiple immune and cellular changes that were activated at different phases of COVID-19. Understanding how a patients gene expression profile changes over time can permit more accurate risk stratification of patients and provide time-dependent personalized treatments with repurposed medications. This creates an opportunity for timely intervention before patients transition to a more severe phase, potentially accelerating patients to recovery.

immunology↗

bioRxiv2021

The ColR/S two-component system is a conserved determinant of host association across Pseudomonas species

Members of the bacterial genus Pseudomonas form mutualistic, commensal and pathogenic associations with diverse hosts. The prevalence of host association across the genus suggests that symbiosis may be a conserved ancestral trait and that distinct symbiotic lifestyles may be more recently evolved. Here we show that the ColR/S two-component system, part of the Pseudomonas core genome, is functionally conserved between Pseudomonas aeruginosa and Pseudomonas fluorescens. Using plant rhizosphere colonization and virulence in a murine abscess model, we show that colR is required for commensalism with plants and virulence in animals. Comparative transcriptomics revealed that the ColR regulon has diverged between P. aeruginosa and P. fluorescens and deleting components of the ColR regulon revealed strain-specific, but not hostspecific, requirements for ColR-dependent genes. Collectively, our results suggest that ColR/S allows Pseudomonas to sense and respond to a host, but that the ColR-regulon has diverged between Pseudomonas strains with distinct lifestyles.

microbiology↗

bioRxiv2021

A curated collection of human vaccination response signatures

Recent advances in high-throughput experiments and systems biology approaches have resulted in hundreds of publications identifying "immune signatures". Unfortunately, these are often described within text, figures, or tables in a format not amenable to computational processing, thus severely hampering our ability to fully exploit this information. Here we present a data model to represent immune signatures, along with the Human Immunology Project Consortium (HIPC) Dashboard (www.hipc-dashboard.org), a web-enabled application to facilitate signature access and querying. The data model captures the biological response components (e.g., genes, proteins, cell types or metabolites) and metadata describing the context under which the signature was identified using standardized terms from established resources (e.g., HGNC, Protein Ontology, Cell Ontology). We have manually curated a collection of >600 immune signatures from >60 published studies profiling human vaccination responses for the current release. The system will aid in building a broader understanding of the human immune response to stimuli by enabling researchers to easily access and interrogate published immune signatures.

bioinformatics↗

bioRxiv2020

The stringent stress response controls proteases and global regulators under optimal growth conditions in Pseudomonas aeruginosa

The bacterial stringent stress response, mediated by the signaling molecule guanosine tetra-phosphate, ppGpp, has recently gained attention as being important during normal cellular growth and as potential new therapeutic target, which warrants detailed mechanistic understanding. Here, we used intracellular protein tracking in Pseudomonas aeruginosa PAO1, which indicated that RelA was bound to the ribosome, while SpoT localized at the cell poles. RNA-Seq was used to investigate the transcriptome of a ppGpp-deficient strain under non-stressful nutrient-rich broth conditions where the mutant grew at the same rate as the parent strain. In exponential growth phase, the lack of ppGpp led to >1,600 transcriptional changes (fold-change cut-off {+/-}1.5), providing further novel insights into the normal physiological role of ppGpp. The stringent response was linked to gene expression of various proteases and secretion systems including aprA, PA0277, impA, and clpP2. The previously observed reduction in cytotoxicity towards red blood cells, in a stringent response mutant, appeared to be due to aprA. Investigation of an aprA mutant in a murine skin infection model, showed increased survival rates of the aprA mutant consistent with previous observations that stringent-response mutants have reduced virulence. In addition, the overexpression of relA, but not induction of ppGpp with serine hydroxamate, dysregulated global transcriptional regulators as well as >30% of the regulatory networks controlled by AlgR, OxyR, LasR, and AmrZ. Together these data expand our knowledge about ppGpp and its regulatory network and role in environmental adaptation. It also confirms its important role throughout the normal growth cycle of bacteria. Significance StatementMicroorganisms need to adapt rapidly to survive harsh environmental changes. Here, we showed the broad influence of the highly studied bacterial stringent stress response under non-stressful conditions that indicate its general physiological importance and might reflect the readiness of bacteria to respond to and activate acute stress responses. Using RNA-Seq to investigate the transcriptional network of Pseudomonas aeruginosa cells revealed that >30% of all genes changed expression in a stringent-response mutant under optimal growth conditions. This included genes regulated by global transcriptional regulators and novel downstream effectors. Our results help to understand the importance of this stress regulator in bacterial lifestyle under relatively unstressed conditions. As such it draws attention to the consequences of targeting this ubiquitous bacterial signaling molecule.

microbiology↗

bioRxiv2020

Mechanistic understanding enables the rational design of salicylanilide combination therapies for Gram-negative infections

One avenue to combat multidrug-resistant Gram-negative bacteria is the co-administration of multiple drugs (combination therapy), which can be particularly promising if drugs synergize. The identification of synergistic drug combinations, however, is challenging. Detailed understanding of antibiotic mechanisms can address this issue by facilitating the rational design of improved combination therapies. Here, using diverse biochemical and genetic assays, we reveal the molecular mechanisms of niclosamide, a clinically-approved salicylanilide compound, and demonstrate its potential for Gram-negative combination therapies. We discovered that Gram-negative bacteria possess two innate resistance mechanisms that reduce their niclosamide susceptibility: a primary mechanism mediated by multidrug efflux pumps and a secondary mechanism of nitroreduction. When efflux was compromised, niclosamide became a potent antibiotic, dissipating the proton motive force (PMF), increasing oxidative stress and reducing ATP production to cause cell death. These insights guided the identification of diverse compounds that synergized with salicylanilides when co-administered (efflux inhibitors, membrane permeabilizers, and antibiotics that are expelled by PMF-dependent efflux), thus suggesting that salicylanilide compounds may have broad utility in combination therapies. We validate these findings in vivo using a murine abscess model, where we show that niclosamide synergizes with the membrane permeabilizing antibiotic colistin against high-density infections of multidrug-resistant Gram-negative clinical isolates. We further demonstrate that enhanced nitroreductase activity is a potential route to adaptive niclosamide resistance but show that this causes collateral susceptibility to clinical nitro-prodrug antibiotics. Thus, we highlight how mechanistic understanding of mode of action, innate/adaptive resistance, and synergy can rationally guide the discovery, development and stewardship of novel combination therapies. ImportanceThere is a critical need for more effective treatments to combat multidrug-resistant Gram-negative infections. Combination therapies are a promising strategy, especially when these enable existing clinical drugs to be repurposed as antibiotics. We reveal the mechanisms of action and basis of innate Gram-negative resistance for the anthelmintic drug niclosamide, and subsequently exploit this information to demonstrate that niclosamide and analogs kill Gram-negative bacteria when combined with antibiotics that inhibit drug efflux or permeabilize membranes. We confirm the synergistic potential of niclosamide in vitro against a diverse range of recalcitrant Gram-negative clinical isolates, and in vivo in a mouse abscess model. We also demonstrate that nitroreductases can confer resistance to niclosamide, but show that evolution of these enzymes for enhanced niclosamide resistance confers a collateral sensitivity to other clinical antibiotics. Our results highlight how detailed mechanistic understanding can accelerate the evaluation and implementation of new combination therapies.

microbiology↗

bioRxiv2018

Broad-spectrum adaptive antibiotic resistance associated with Pseudomonas aeruginosa mucin-dependent surfing motility

Surfing motility is a novel form of surface adaptation exhibited by the nosocomial pathogen, Pseudomonas aeruginosa, in the presence of the glycoprotein mucin that is found in high abundance at mucosal surfaces especially the lungs of cystic fibrosis and bronchiectasis patients. Here we investigated the adaptive antibiotic resistance of P. aeruginosa under conditions in which surfing occurs compared to cells undergoing swimming. P. aeruginosa surfing cells were significantly more resistant to several classes of antibiotics including aminoglycosides, carbapenems, polymyxins, and fluroquinolones. This was confirmed by incorporation of antibiotics into growth medium, which revealed a concentration-dependent inhibition of surfing motility that occurred at concentrations much higher than those needed to inhibit swimming. To investigate the basis of resistance, RNA-Seq was performed and revealed that surfing influenced the expression of numerous genes. Included amongst genes dysregulated under surfing conditions were multiple genes from the Pseudomonas resistome, which are known to affect antibiotic resistance when mutated. Screening transposon mutants in these surfing-dysregulated resistome genes revealed that several of these mutants exhibited changes in susceptibility to one or more antibiotics under surfing conditions, consistent with a contribution to the observed adaptive resistance. In particular, several mutants in resistome genes, including armR, recG, atpB, clpS, nuoB, and certain hypothetical genes such as PA5130, PA3576 and PA4292, showed contributions to broad-spectrum resistance under surfing conditions and could be complemented by their respective cloned genes. Therefore, we propose that surfing adaption led to extensive multidrug adaptive resistance as a result of the collective dysregulation of diverse genes.

microbiology↗