Biology subjects

Edwards, A. M.

Publications and source records attributed to Edwards, A. M..

At least 19 recordsLinked to original sources

bioRxiv2026

A novel ciprofloxacin analogue enables daptomycin-mediated killing of resistant Staphylococcus aureus by increasing septum formation

Quinolone antibiotics such as ciprofloxacin inhibit DNA gyrase, leading to DNA double-strand breaks that result in rapid bacterial killing and induction of the mutagenic SOS DNA repair response. By contrast, the ciprofloxacin analogue IMP-1700 inhibits ciprofloxacin-induced SOS, suggesting a novel mechanism of action. Here, we provide evidence that IMP-1700 targets the quinolone binding domain of DNA gyrase but triggers a significantly higher frequency of division septa in S. aureus compared with other DNA gyrase targeting antibiotics, including ciprofloxacin. In keeping with this finding, the lipopeptide antibiotic daptomycin, which targets the division septum, bound more strongly to IMP-1700-treated cells relative to S. aureus exposed to other DNA gyrase inhibitors, leading to increased bacterial killing. This finding extended to a panel of paired daptomycin susceptible and resistant clinical isolates. We conclude that the ciprofloxacin analogue IMP-1700 has distinct effects on the cell envelope of S. aureus, despite appearing to share the same target as the parent drug, which result in the resensitisation of daptomycin resistant bacteria to the lipopeptide antibiotic.

microbiology↗

bioRxiv2026

Murepavadin is a broad-spectrum outer membrane permeabiliser

Murepavadin is a Pseudomonas-specific antibiotic that targets LPS transport protein LptD. However, whilst the mode of action of murepavadin is well defined, the mechanism by which the drug gains access to LptD remains unresolved. Here, we demonstrate a self-directed uptake mechanism for murepavadin, whereby binding to lipid A induces outer membrane disruption, enabling entry of the antibiotic into the periplasm and access to LptD. Murepavadin-LPS interactions were not specific to P. aeruginosa, however, and were found to cause OM disruption across a wide range of Gram-negative bacteria, resulting in increased antibiotic susceptibility. We also discovered that murepavadin-mediated OM disruption sensitised E. coli to the membrane attack complex of the complement system. In conclusion, murepavadin is a broad-spectrum membrane permeabiliser, which results in increased bacterial susceptibility to antibiotics and host defences.

microbiology↗

bioRxiv2026

Macrocyclic Peptide Tools for Huntingtin-bound HAP40

Huntingtons disease is a fatal neurodegenerative disorder caused by expansion of a cytosine-adenosine-guanine repeat in exon 1 of the Huntingtin (HTT) gene, resulting in a polyglutamine-expanded HTT protein. Although the genetic cause of Huntingtons is well defined, the molecular functions of HTT and the mechanisms linking polyglutamine expansion to neurodegeneration remain incompletely understood. Huntingtin Associated Protein 40 kDa (HAP40) is a key HTT interaction partner that forms a stable complex with HTT and is increasingly recognized as an important player in the HTT structure-function paradigm. However, investigation of HAP40 biology has been limited by a lack of tools capable of directly targeting endogenous protein. Here, we report the discovery and characterization of a panel of nanomolar-affinity macrocyclic peptides targeting HAP40 identified using Random nonstandard Peptide Integrated discovery platform. We characterized macrocycle binding in vitro using surface plasmon resonance, fluorescence polarization, and hydrogen-deuterium exchange mass spectrometry, revealing selective, high-affinity engagement of distinct epitopes on HAP40. We further demonstrate that these macrocycles engage endogenous HAP40 in cellular lysates, enable selective isolation of HAP40-containing protein complexes using macrocycle precipitations and insights into interaction partners of distinct HTT and HAP40 proteoforms. Together, these macrocycles establish a new toolkit for investigating HTT-HAP40 biology and provide a framework for dissecting HAP40-specific functions relevant to Huntingtons disease pathogenesis.

molecular biology↗

bioRxiv2026

Commonly prescribed medicines antagonise anti-MRSA antibiotics and select for resistance

Many commonly prescribed non-antibiotic medicines have off-target antimicrobial activity, yet their impact on antibiotic efficacy remains poorly understood. In this study, we investigated eight widely used UK prescription medicines and identified simvastatin, amlodipine, and fluoxetine as growth inhibitory towards methicillin-resistant Staphylococcus aureus (MRSA). These drugs disrupt bacterial membranes, with amlodipine and fluoxetine also triggering stress responses linked to cell wall and membrane damage. Further mechanistic analysis using transposon mutant screening revealed that simvastatin impairs cell wall synthesis by inhibiting the mevalonate pathway. Notably, checkerboard assays demonstrated antagonistic interactions: simvastatin reduced the efficacy of {beta}-lactams and vancomycin, amlodipine with vancomycin and daptomycin, and fluoxetine with vancomycin activity. Prolonged exposure to these drugs also accelerated resistance development to vancomycin and daptomycin. Together, these findings underscore the potential for commonly prescribed non-antibiotic medicines to undermine antibiotic therapy, warranting further study given the rising S. aureus treatment failures.

microbiology↗

bioRxiv2025

Cell type specific analysis of ALS associated proteins reveals immune-regulated targets

A substantial fraction of amyotrophic lateral sclerosis (ALS)-associated proteins remain poorly characterized, in part because of the limited availability of validated research antibodies. We established knockout (KO)-based antibody characterization workflows and demonstrated that widely used antibodies against the major ALS-associated protein C9orf72 lacked specificity (Laflamme et al., 2019). We subsequently scaled this framework to systematically benchmark research antibodies, revealing that up to 61% fail to perform as recommended by manufacturers (Ayoubi et al., 2023). Here, we extend this approach by establishing the ALS-Reproducible Antibody Platform (ALS-RAP), a comprehensive effort to generate a publicly available dataset of KO-validated antibodies targeting proteins encoded by ALS risk genes. In total, we characterized 303 antibodies against 33 ALS-associated proteins to identify high-quality reagents for use in western blot, immunoprecipitation, and immunofluorescence. Using these antibodies, we profiled protein levels across human induced pluripotent stem cell (iPSC)-derived and primary neurological cell types. These analyses revealed diverse cellular distributions and higher levels of several ALS-associated proteins in glial populations, consistent with emerging evidence for immune contributions to ALS. Together, ALS-RAP provides a validated antibody toolbox and protein expression resource to support the study of ALS-associated proteins.

neuroscience↗

bioRxiv2025

Small molecule inhibitors of the NorA multidrug efflux pump potentiate antibiotic activity by binding the outward-open conformation

Antibiotic resistance is among the greatest threats of the modern era. Multidrug efflux pumps expel antibiotics from bacterial cells and present a particular challenge by conferring resistance to a broad range of antibiotic classes; however, there is currently a lack of potent and selective inhibitors. Here, we report the discovery of IMP-2380, a drug-like chemical probe for the multidrug efflux pump NorA that delivers low-nanomolar potentiation of ciprofloxacin activity in vitro and activity in an in vivo S. aureus infection model. A phenotypic high-throughput screen for inhibitors of the ciprofloxacin-activated SOS DNA repair pathway in methicillin-resistant Staphylococcus aureus (MRSA) identified hit compounds targeting NorA, and subsequent optimization established IMP-2380 as the most potent NorA inhibitor discovered to date. The structure of NorA bound to IMP-2380 was solved by cryo-electron microscopy at 2.52 [A] resolution, revealing that the small molecule locks the pump in the outward-open conformation. This closes the inner face and prevents antibiotics binding from the cytosol, providing an explanation for the exceptional potency of IMP-2380 and structure-activity relationship across the series. IMP-2380 represents an in vivo active NorA inhibitor, functioning via a structurally defined outward-open binding mode, and will enable future exploration of NorA as a druggable target to combat antibiotic resistance.

biochemistry↗

bioRxiv2025

High-Affinity, Structure-Validated and Selective Macrocyclic Peptide Tools for Chemical Biology Studies of Huntingtin

Huntingtons disease (HD) is a fatal neurodegenerative disorder caused by a CAG repeat expansion in the Huntingtin (HTT) gene, with no disease-modifying therapies currently available. The precise molecular function of the HTT protein is unclear, and the lack of selective chemical tools has limited functional studies. We have identified and characterized macrocyclic peptide binders targeting HTT. These binders exhibit low-nanomolar affinity in vitro and engage distinct HTT and HTT-HAP40 interfaces, as revealed by hydrogen-deuterium exchange mass spectrometry and cryo-electron microscopy. Chemoproteomics confirmed selective binding in cell extracts from wildtype but not HTT-null cell lines. HAP40 consistently and stoichiometrically co-purified with HTT across cell lines, including with HTT variants containing different CAG repeat lengths, highlighting the broad presence of the HTT-HAP40 complex. Significance StatementHuntingtin (HTT) is a large, essential protein with conserved roles in development, intracellular trafficking, and protein homeostasis, yet its precise molecular functions remain incompletely defined. Here, we report the first high-affinity, selective, and structurally validated macrocyclic peptide ligands for HTT. These chemical tools bind HTT and its complex with HAP40 across polyglutamine repeat lengths, enabling direct interrogation of HTT structure and function in health and disease contexts. By overcoming longstanding barriers to studying HTT at the molecular level, these ligands open new avenues for discovery in neurobiology, cell biology, and offer opportunities for therapeutic development. This study delivers urgently needed tools to both the Huntingtons disease field and the broader scientific community seeking to understand this elusive and biologically fundamental protein.

biochemistry↗

bioRxiv2025

Polymyxin heteroresistance in Klebsiella oxytoca

Antibiotic heteroresistance presents a growing public health concern since the phenotype is associated with treatment failure and is hard to detect using conventional diagnostic testing. In this study, we characterized polymyxin B heteroresistance in a collection of clinical and environmental isolates of Klebsiella oxytoca, an opportunistic pathogen associated with hospital-acquired infections. All six of the isolates tested exhibited heteroresistance, indicated by a 16-fold difference between the highest non-inhibitory concentration (2 {micro}g/mL) and the minimum inhibitory concentration (32-64 {micro}g/mL) observed in population analysis profile (PAP) assays. Heteroresistance was found to be due to the presence of a stable sub-population of resistant bacteria and was unaffected by growth phase or the presence of host antimicrobial factors present in human serum. MALDI-TOF analysis revealed L-Ara4N modifications of the lipid A of resistant sub-populations. This pilot study identifies polymyxin heteroresistance in K. oxytoca may complicate treatment of infections caused by this organism.

microbiology↗

bioRxiv2025

Polymyxin B lethality requires energy-dependent outer membrane disruption

Polymyxin antibiotics target lipopolysaccharide (LPS) in both membranes of the bacterial cell envelope, leading to bacterial killing through a mechanism that remains poorly understood. Here, we demonstrate that metabolic activity is essential for polymyxin lethality and leverage this insight to determine its mode of action. Polymyxin B (PmB) efficiently killed exponential phase E. coli but was unable to eliminate stationary phase cells unless a carbon source was available. Antibiotic lethality correlated with surface protrusions, LPS loss, and a significant reduction in outer membrane (OM) barrier function, processes that required LPS synthesis and transport. While the energy-dependent OM disruption was not directly lethal, it facilitated PmB access to the inner membrane (IM), which the antibiotic permeabilised in an energy-independent manner, leading to cell death. Finally, we show that the polymyxin resistance determinant MCR-1 prevents PmB-mediated LPS loss and OM protrusions and thereby renders the antibiotic ineffective.

microbiology↗

bioRxiv2025

High-throughput protein target mapping enables accelerated bioactivity discovery for ToxCast and PFAS compounds

Chemical pollution is a global threat to human health, yet the toxicity mechanism of most contaminants remains unknown. Here, we applied an ultrahigh-throughput affinity-selection mass spectrometry (AS-MS) platform to systematically identify protein targets of prioritized chemical contaminants. After benchmarking the platform, we screened 50 human proteins against 481 prioritized chemicals, including 446 ToxCast chemicals and 35 per-and polyfluoroalkyl substances (PFAS). Among 24,050 interactions assessed, we discovered 35 novel interactions involving 14 proteins, with fatty acid-binding proteins (FABPs) emerging as the most ligandable protein family. Given this, we selected FABPs for further validation, which revealed a distinct PFAS binding pattern: legacy PFAS selectively bound to FABP1, whereas replacement compounds, PFECAs, unexpectedly interacted with all FABPs. X-ray crystallography further revealed that the ether group enhances molecular flexibility of alternative PFAS, to accommodate the binding pockets of FABPs. Our findings demonstrate that AS-MS is a robust platform for the discovery of novel protein targets beyond the scope of the ToxCast program and highlight the broader protein-binding spectrum of alternative PFAS as potential regrettable substitutes.

pharmacology and toxicology↗

bioRxiv2024

ABHD2 activity is not required for the non-genomic action of progesterone on human sperm

Study questionIs the hydrolase ABHD2 required for progesterone-induced Ca2+ influx via CatSper and the resulting motility responses in human sperm? Summary answerProgesterone-induced Ca2+ influx via CatSper and the resulting motility responses in human sperm do not require ABHD2 activity. What is known alreadySperm motility is tightly regulated by signalling pathways that are activated as sperm ascend the female reproductive tract, including progesterone triggering Ca2+ influx via the CatSper channel and inducing hyperactivated motility needed for fertilization. This process is thought to involve ABHD2, which may hydrolyse the endogenous CatSper inhibitor 2-arachidonoylglycerol (2-AG), thereby relieving inhibition and enabling calcium entry into the flagellum. Study design, size, durationPotent small molecule inhibitors of ABHD2 activity were synthesized, characterized, and used as tools to scrutinize the role of ABHD2 in activation of CatSper and regulation of sperm motility. Participants/materials, setting, methodsDerivatives of published ABHD2 inhibitors were optimised for in vitro potency and cellular activity and subsequently tested in human sperm motility and Ca2+ influx assays. Main results and the role of chanceProgesterone does not activate ABHD2 in vitro. In addition, inhibition of ABHD2 in human sperm has no effect on progesterone-induced Ca2+ influx through CatSper nor on basal or progesterone-induced hyperactivated motility. This demonstrates that ABHD2 activity is, in fact, not required for the non-genomic action of progesterone on human sperm. Large scale datanone Limitations, reasons for cautionWe examined the effects of inhibition of the enzymatic activity of ABHD2. We cannot exclude that ABHD2 functions as a part of a larger multiprotein complex, in which it may play a structural role independent of its hydrolase activity. Wider implications of the findingsThis study presents conclusive evidence that ABHD2 does not bind progesterone and that its hydrolase activity is not required for progesterone activation of CatSper and resulting changes in motility of human sperm. These results highlight the need for further research to elucidate the mechanism underlying the non-genomic action of progesterone on human sperm. Study funding/competing interest(s)This publication is based on research funded by the Gates Foundation. The findings and conclusions contained within are those of the authors and do not necessarily reflect positions or policies of the Gates Foundation. LT, CB, and TS were supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - project numbers 329621271 (CRU326; CB, TS), and 404595355 (Research Training Group "Chemical biology of ion channels (Chembion); LT, TS). This work was funded by the German Federal Ministry of Education and Research (BMBF) within the framework of Contraception Research, grant number 01GR2501A and 01GR2502A. A.A., K.V., A.T., N.D., A.H., M.W. and R.L. are employees of Nuvisan ICB GMBH, Berlin, Germany. Nuvisan is recipient of a Gates Foundation grant. A.A is associate editor of Human Reproduction Open.

cell biology↗

bioRxiv2024

A resource to enable chemical biology and drug discovery of WDR Proteins

Protein class-focused drug discovery has a long and successful history in pharmaceutical research, yet most members of druggable protein families remain unliganded, often for practical reasons. Here we combined experiment and computation to enable discovery of ligands for WD40 repeat (WDR) proteins, one of the largest human protein families. This resource includes expression clones, purification protocols, and a comprehensive assessment of the druggability for hundreds of WDR proteins. We solved 21 high resolution crystal structures, and have made available a suite of biophysical, biochemical, and cellular assays to facilitate the discovery and characterization of small molecule ligands. To this end, we use the resource in a hit-finding pilot involving DNA-encoded library (DEL) selection followed by machine learning (ML). This led to the discovery of first-in-class, drug-like ligands for 9 of 20 targets. This result demonstrates the broad ligandability of WDRs. This extensive resource of reagents and knowledge will enable further discovery of chemical tools and potential therapeutics for this important class of proteins.

biochemistry↗

bioRxiv2023

Assessing the performance of commercial reagent antibodies

Antibodies are critical reagents to detect and characterize proteins. It is commonly understood that many commercial antibodies do not recognize their intended targets, but information on the scope of the problem remains largely anecdotal, and as such, feasibility of the goal of at least one potent and specific antibody targeting each protein in a proteome cannot be assessed. Focusing on antibodies for human proteins, we have scaled a standardized characterization approach using parental and knockout cell lines (Laflamme et al., 2019) to assess the performance of 614 commercial antibodies for 65 neuroscience-related proteins. Side-by-side comparisons of all antibodies against each target, obtained from multiple commercial partners, demonstrates that: i) more than 50% of all antibodies failed in one or more tests, ii) yet, [~]50-75% of the protein set was covered by at least one high-performing antibody, depending on application, suggesting that coverage of human proteins by commercial antibodies is significant; and iii) recombinant antibodies performed better than monoclonal or polyclonal antibodies. The hundreds of underperforming antibodies identified in this study were found to have been used in a large number of published articles, which should raise alarm. Encouragingly, more than half of the underperforming commercial antibodies were reassessed by the manufacturers, and many had alterations to their recommended usage or were removed from the market. This first such study helps demonstrate the scale of the antibody specificity problem but also suggests an efficient strategy toward achieving coverage of the human proteome; mine the existing commercial antibody repertoire, and use the data to focus new renewable antibody generation efforts.

molecular biology↗

bioRxiv2023

Antimicrobial peptide glatiramer acetate targets Pseudomonas aeruginosa lipopolysaccharides to breach membranes without altering lipopolysaccharide modification

Antimicrobial peptides (AMPs) are key components of innate immunity across all kingdoms of life. Both natural and synthetic AMPs are receiving renewed attention in the efforts to combat the antimicrobial resistance (AMR) crisis and the loss of antibiotic efficacy. The gram-negative pathogen Pseudomonas aeruginosa is one of the most concerning infectious bacteria in AMR, particularly in people with cystic fibrosis (CF) where respiratory infections are difficult to eradicate and are associated with increased morbidity and mortality. Cationic AMPs exploit the negative charge of lipopolysaccharides (LPS) on P. aeruginosa to bind to and disrupt the bacterial membrane(s) and cause lethal damage. P. aeruginosa modifies its LPS, via environmental or genetic factors, to neutralise the charge of the cell and evade AMP killing. Free-LPS is also a component of CF sputum, as is anionic extracellular DNA (eDNA), each of which can bind AMPs by electrostatic interaction. Both free LPS and eDNA also feed into pro-inflammatory cycles. Glatiramer acetate (GA) is a random peptide co-polymer of glycine, lysine, alanine, and tyrosine and used as drug in the treatment of multiple sclerosis (MS); we have previously shown GA to be an AMP which synergises with tobramycin against P. aeruginosa from CF, functioning via bacterial membrane disruption. Here, we demonstrate direct binding and sequestration/neutralisation of P. aeruginosa LPS in keeping with GAs ability to disrupt the outer membrane. Binding and neutralisation of eDNA was also seen. At CF-relevant concentrations, however, neither strongly inhibited membrane disruption by GA. Furthermore, in both type strains and clinical CF isolates of P. aeruginosa, exposure to GA did not result in increased modification of the Lipid A portion of LPS or in increased expression of genetically encoded systems involved in AMP sensing and LPS modification. With this low selective pressure on P. aeruginosa for known AMP resistance mechanisms, the potential to neutralise pro-inflammatory CF sputum components, as well as the previously described enhancement of antibiotic function, GA is a promising candidate for drug repurposing.

microbiology↗

bioRxiv2023

IS1-related large-scale deletion of chromosomal regions harbouring oxygen-insensitive nitroreductase gene nfsB causes nitrofurantoin heteroresistance in Escherichia coli

Nitrofurantoin is a broad-spectrum first-line antimicrobial used for managing uncomplicated urinary tract infection. Loss-of-function mutations in chromosomal genes nfsA, nfsB, and ribE of Escherichia coli are known to reduce nitrofurantoin susceptibility. Here, we report monoclonal nitrofurantoin heteroresistance in E. coli and a novel genetic mechanism associated with this phenomenon. Subpopulations with reduced nitrofurantoin susceptibility in cultures of two E. coli blood strains were identified using population analysis profiling. Four colonies of each strain growing on agar with 0.5xMIC nitrofurantoin were sub-cultured in broth with 0.5xMIC nitrofurantoin (n=2) or without nitrofurantoin (n=2). Moreover, one colony of each strain growing without nitrofurantoin exposure was selected as a reference for genomic comparison. Whole-genome sequencing of all isolates were conducted on Illumina and Nanopore MinION systems. Both strains had a nitrofurantoin MICs of 64 mg/L. The proportion of cells grown at 0.5xMIC was two and 99 per million, respectively, which is distinct to that of a homogeneously susceptible or resistant isolate. All isolates grown at 0.5xMIC had 11-66 kbp deletions in chromosomal regions harbouring nfsB, and all these deletions were immediately adjacent to IS1-family insertion sequences. Although this study is limited to E. coli and nitrofurantoin, our findings suggest IS1-associated genetic deletion represents a hitherto unrecognised mechanism of heteroresistance that could compromise infection management and impact conventional antimicrobial susceptibility testing. Impact statementNitrofurantoin is widely used for treating and preventing urinary tract infection. Prevalence of nitrofurantoin resistance generally is low in E. coli. Here, we report nitrofurantoin heteroresistance in two E. coli blood strains and attribute this phenotype to IS1-associated deletion of chromosomal regions harbouring oxygen-insensitive nitroreductase gene nfsB. Our discoveries demonstrate a novel genetic mechanism of heteroresistance and suggest detecting nitrofurantoin heteroresistance in E. coli urinary isolates for improving prescribing. Data summaryWhole-genome sequencing reads and genome assemblies generated in this study have been deposited under BioProject PRJEB58678 in the European Nucleotide Archive (ENA). Accession numbers are listed in Supplementary Table 1. Previously generated Illumina whole-genome sequencing reads of parental isolates EC0026B and EC0880B are available under ENA accessions ERR3142418 and ERR3142524, respectively.

microbiology↗

bioRxiv2023

Staphylococcal host adaptation compromises neutrophil killing by concealing bound opsonins with peptidoglycan

The bacterial pathogen Staphylococcus aureus adapts to the host environment by increasing the thickness of its cell wall. However, the impact of cell wall thickening on susceptibility to host defences is unclear. Here, we show that as bacteria adapted to serum, the resulting increase in cell wall thickness led to a reduction in the exposure of bound antibody and complement and a corresponding reduction in phagocytosis and killing by neutrophils. The exposure of opsonins bound to protein antigens or LTA were most significantly reduced, whilst opsonisation by IgG against wall teichoic acid or peptidoglycan was largely unaffected. Partial digestion of accumulated cell wall in host adapted cells using the enzyme lysostaphin restored opsonin exposure and promoted phagocytosis and killing. Concordantly, the antibiotic fosfomycin inhibited cell wall remodelling and maintained full susceptibility of S. aureus to opsonophagocytic killing by neutrophils. These findings reveal that the adaptation of S. aureus to the host environment reduces the ability of the immune system to detect and kill this pathogen through reduced exposure of protein- and LTA-bound opsonins via cell wall remodelling.

microbiology↗

bioRxiv2022

Human serum induces daptomycin tolerance in Enterococcus faecalis and viridans group streptococci

Daptomycin is a membrane-targeting lipopeptide antibiotic used in the treatment of infective endocarditis caused by multidrug-resistant Gram-positive bacteria such as Staphylococcus aureus, enterococci and viridans group streptococci. Despite demonstrating excellent in vitro activity and a low prevalence of resistant isolates, treatment failure is a significant concern, particularly for enterococcal infection. We have shown recently that human serum triggers daptomycin tolerance in S. aureus, but it was not clear if a similar phenotype occurred in other major infective endocarditis pathogens. We found that Enterococcus faecalis, Streptococcus gordonii or Streptococcus mutans grown under standard laboratory conditions were efficiently killed by daptomycin, whereas bacteria pre-incubated in human serum survived exposure to the antibiotic, with >99% cells remaining viable. Incubation of enterococci or streptococci in serum led to peptidoglycan accumulation, as shown by increased incorporation of the fluorescent D-amino analogue HADA. Inhibition of peptidoglycan accumulation using the antibiotic fosfomycin resulted in a >10-fold reduction in serum-induced daptomycin tolerance, demonstrating the important contribution of the cell wall to the phenotype. We also identified a small contribution to daptomycin tolerance in E. faecalis from cardiolipin synthases, although this may reflect the inherent susceptibility of cardiolipin-deficient mutants. In summary, serum-induced daptomycin tolerance is a consistent phenomenon between Gram-positive infective endocarditis pathogens, but it may be mitigated using currently available antibiotic combination therapy.

microbiology↗

bioRxiv2022

XerC is required for the repair of antibiotic- and immune-mediated DNA damage in Staphylococcus aureus

To survive in the host environment, pathogenic bacteria need to be able repair DNA damage caused by both antibiotics and the immune system. The SOS response is a key bacterial pathway to repair DNA double strand breaks and may therefore be a good target for novel therapeutics to sensitise bacteria to antibiotics and the immune response. However, the genes required for the SOS response in Staphylococcus aureus have not been fully established. Therefore, we carried out a screen of mutants involved in various DNA repair pathways to understand which were required for induction of the SOS response. This led to the identification of 16 genes that may play a role in SOS response induction, and of these, 3 that affected susceptibility of S. aureus to ciprofloxacin. Further characterisation revealed that, in addition to ciprofloxacin, loss of the tyrosine recombinase XerC increased the susceptibility of S. aureus to various classes of antibiotics, as well as to host immune defences. Therefore, the inhibition of XerC may be a viable therapeutic approach to sensitise S. aureus to both antibiotics and the immune response.

microbiology↗