Biology subjects

Ferrara, K.

Publications and source records attributed to Ferrara, K..

7 recordsLinked to original sources

bioRxiv2026

Ferrosome Organelles Spatially Insulate a Redox-Active Ferrous Phosphate Biomineral from Cytosolic ROS Chemistry

Ferrosomes are recently discovered lipid-bound bacterial organelles that store iron as iron-phosphate biominerals, yet the chemical nature and physiological consequences of ferrosome-stored iron remain poorly understood. Here, we combined X-ray absorption spectroscopy (XAS), electron microscopy, inductively coupled plasma mass spectrometry (ICP-MS), and physiological analyses to characterize ferrosome iron in Clostridioides difficile. XAS analysis of isolated ferrosomes revealed an amorphous iron-phosphate biomineral containing mixed Fe(II)/Fe(III), consistent with partial oxidation during aerobic isolation. In contrast, whole-cell XAS of intact anaerobically maintained cells demonstrated that ferrosomes predominantly contain a structurally disordered ferrous phosphate biomineral with local Fe-O-P coordination features similar to those of vivianite. Upon air exposure, this ferrous biomineral rapidly oxidized to a ferric phosphate-like state, revealing a highly oxygen-sensitive iron-storage phase. Despite containing abundant redox-active Fe(II), ferrosome-stored iron contributed minimally to the cytosolic labile iron pool. Consistent with this observation, isolated ferrosomes exhibited little ROS-generating activity, and ferrosome-overproducing cells displayed no substantial increase in sensitivity to oxygen, peroxide, or paraquat stress relative to ferrosome-deficient controls. Together, these results establish ferrosomes as iron-storage organelles that sequester redox-active Fe(II) in a mineralized ferrous phosphate phase, limiting its participation in cytosolic ROS chemistry and providing a mechanism for the safe storage of reactive iron. Significance StatementIron is essential for life but can also damage cells because ferrous iron drives oxidative stress. How cells store large amounts of ferrous iron while limiting toxicity therefore remains a fundamental biological question. Ferrosomes are recently discovered bacterial organelles that store iron as iron-phosphate biominerals, but the chemical nature and physiological consequences of ferrosome-associated iron remained unknown. Using Fe K-edge X-ray absorption spectroscopy, we show that ferrosomes in Clostridioides difficile contain a redox-sensitive ferrous phosphate biomineral. Physiological analyses demonstrate that this iron is largely inaccessible to cytosolic reactive oxygen species (ROS) chemistry. These findings reveal that bacteria can combine biomineralization and subcellular compartmentalization to maintain large intracellular iron reservoirs while limiting iron-dependent oxidative damage.

microbiology↗

bioRxiv2026

Microbubble-Enhanced Focused Ultrasound Improves Targeted Adeno-Associated Virus Delivery in Brain Tumors Quantified by PET Imaging

Gene therapy using adeno-associated virus (AAV) vectors shows promise for cancer treatment through molecular intervention, yet achieving sufficient and targeted delivery to brain tumors via systemic administration remains limited by the biological barriers. Here, we investigate whether microbubble-enhanced focused ultrasound (MB-FUS) improves targeted delivery of systemically administered AAV9 to orthotopic gliomas, using quantitative PET imaging of 64Cu-radiolabeled AAV9 vectors and fluorescent reporter expression to assess biodistribution and functional efficacy. At 21 hours after injection, 64Cu-AAV9 accumulation was 3.2-fold higher in FUS-treated tumors compared to non-FUS-treated tumors (n=3, p=0.004). Quantitative PCR analysis of tumor tissue at the same timepoint confirmed a 6.4-fold increase in genome copies in FUS-treated tumors (p=0.0003). The enhanced vector delivery translated to a 5.3-fold increase in optical reporter protein expression in FUS-treated compared to control tumors (p=0.0002) at 17 days post-treatment. These results establish that MB-FUS enables spatially-targeted AAV delivery with quantifiable enhancement in both acute vector biodistribution and downstream transgene expression. The integration of radiolabeled AAV with PET imaging provides a non-invasive methodology for real-time assessment of vector delivery and optimization of treatment protocol for brain cancer gene therapy. HighlightsO_LIMB-FUS enables targeted systemic AAV delivery to brain tumors. C_LIO_LIMB-FUS enhanced vector delivery translates to increased transgene expression in gliomas. C_LIO_LIPET imaging of radiolabeled AAV allows non-invasive tracking of gene therapy vectors. C_LIO_LIReal-time imaging validates spatially-controlled gene delivery for brain cancer. C_LI

bioengineering↗

bioRxiv2025

An Inducible CRISPRi system for phenotypic analysis of essential genes in Pseudomonas aeruginosa

Precise and tunable genetic tools are essential for high throughput functional genomics. To address this need in the important gram-negative pathogen Pseudomonas aeruginosa, we developed and characterized a tightly regulated CRISPRi system that enables precise and tunable repression of essential genes. The system utilizes a rhamnose-inducible promoter to control both the Streptococcus pasteurianus-derived dCas9 and gene-specific sgRNAs, each encoded on separate plasmids for modularity and efficiency. The combination of tight regulation and high conjugation efficiency facilitated the rapid and facile construction of strains with regulated depletion of 16 essential genes spanning diverse pathways. Comparison of phenotypes across the different genetically depleted strains, including growth rate, susceptibility to antibiotics, and changes in transcriptional programs, revealed novel aspects of gene function or small molecule mechanism of action. Finally, the rhamnose-inducible CRISPRi system supports the generation and stable maintenance of pooled mutant libraries, thereby paving the way for future genome-wide, systematic assessment of individual gene vulnerabilities, which will provide critical insights for target prioritization in antibiotic discovery efforts against this recalcitrant pathogen. IMPORTANCECRISPRi has become an invaluable tool for studying genetics. In particular, the ability to knockdown genes enables the study of essential genes and their role in cell survival. However, a tightly regulated gene knockdown system is required to gain valuable insights into these vulnerable genes by virtue of their essentiality. We report a tightly regulated CRISPRi system to study the biology of essential gene perturbations in Pseudomonas aeruginosa, an important gram-negative pathogen that causes severe infections and is increasingly resistant to current antibiotics. This system enables characterization of both chemical genetic interactions between small molecules and specific gene depletions, and the impact of genetic perturbations on transcriptional networks. Genetic perturbations using CRISPRi can thus further our understanding of basic biology with translation towards future antimicrobial development.

microbiology↗

bioRxiv2024

Perturbation-Specific Transcriptional Mapping facilitates unbiased target elucidation of antibiotics

The rising prevalence of antibiotic resistance threatens human health. While more sophisticated strategies for antibiotic discovery are being developed, target elucidation of new chemical entities remains challenging. In the post-genomic era, expression profiling can play an important role in mechanism-of-action (MOA) prediction by reporting on the cellular response to perturbation. However, the broad application of transcriptomics has yet to fulfill its promise of transforming target elucidation due to challenges in identifying the most relevant, direct responses to target inhibition. We developed an unbiased strategy for MOA prediction, called Perturbation-Specific Transcriptional Mapping (PerSpecTM), in which large-throughput expression profiling of wildtype or hypomorphic mutants, depleted for essential targets, enables a computational strategy to address this challenge. We applied PerSpecTM to perform reference-based MOA prediction based on the principle that similar perturbations, whether chemical or genetic, will elicit similar transcriptional responses. Using this approach, we elucidated the MOAs of three new molecules with activity against Pseudomonas aeruginosa by comparing their expression profiles to those of a reference set of antimicrobial compounds with known MOAs. We also show that transcriptional responses to small molecule inhibition resemble those resulting from genetic depletion of essential targets by CRISPRi by PerSpecTM, demonstrating proof-of-concept that correlations between expression profiles of small molecule and genetic perturbations can facilitate MOA prediction when no chemical entities exist to serve as a reference. Empowered by PerSpecTM, this work lays the foundation for an unbiased, readily scalable, systematic reference-based strategy for MOA elucidation that could transform antibiotic discovery efforts. Significance StatementNew antibiotics are critically needed in the face of increasing antibiotic resistance. However, mechanism-of-action (MOA) elucidation remains challenging and imposes a major bottleneck in antibiotic discovery and development. Building on the principle that molecules with similar MOAs elicit similar transcriptional responses, we have developed a highly scalable strategy for MOA prediction in the important bacterial pathogen Pseudomonas aeruginosa based on correlations between the expression profiles of new molecules and known perturbations, either small molecule inhibition by known antibiotics or transcriptional repression of essential targets by CRISPRi. By rapidly assigning MOAs to three new molecules with anti-pseudomonal activity, we provide proof-of-concept for a rapid, comprehensive, systematic, reference-based approach to MOA prediction with the potential to transform antibiotic discovery efforts.

genomics↗

bioRxiv2024

Multiplexed screen identifies a Pseudomonas aeruginosa-specific small molecule targeting the outer membrane protein OprH and its interaction with LPS

SUMMARYThe surge of antimicrobial resistance threatens efficacy of current antibiotics, particularly against Pseudomonas aeruginosa, a highly resistant gram-negative pathogen. The asymmetric outer membrane (OM) of P. aeruginosa combined with its array of efflux pumps provide a barrier to xenobiotic accumulation, thus making antibiotic discovery challenging. We adapted PROSPECT1, a target-based, whole-cell screening strategy, to discover small molecule probes that kill P. aeruginosa mutants depleted for essential proteins localized at the OM. We identified BRD1401, a small molecule that has specific activity against a P. aeruginosa mutant depleted for the essential lipoprotein, OprL. Genetic and chemical biological studies identified that BRD1401 acts by targeting the OM {beta}-barrel protein OprH to disrupt its interaction with LPS and increase membrane fluidity. Studies with BRD1401 also revealed an interaction between OprL and OprH, directly linking the OM with peptidoglycan. Thus, a whole-cell, multiplexed screen can identify species-specific chemical probes to reveal novel pathogen biology.

microbiology↗

bioRxiv2023

Engineered probiotics limit CNS autoimmunity by stabilizing HIF-1α in dendritic cells

Dendritic cells (DCs) control the generation of self-reactive pathogenic T cells. Thus, DCs are considered attractive therapeutic targets for autoimmune diseases. Using single-cell and bulk transcriptional and metabolic analyses in combination with cell-specific gene perturbation studies we identified a negative feedback regulatory pathway that operates in DCs to limit immunopathology. Specifically, we found that lactate, produced by activated DCs and other immune cells, boosts NDUFA4L2 expression through a mechanism mediated by HIF-1. NDUFA4L2 limits the production of mitochondrial reactive oxygen species that activate XBP1-driven transcriptional modules in DCs involved in the control of pathogenic autoimmune T cells. Moreover, we engineered a probiotic that produces lactate and suppresses T-cell autoimmunity in the central nervous system via the activation of HIF-1/NDUFA4L2 signaling in DCs. In summary, we identified an immunometabolic pathway that regulates DC function, and developed a synthetic probiotic for its therapeutic activation.

immunology↗

bioRxiv2022

Highly Excretable Gold Supraclusters for Translatable In Vivo Raman Imaging of Tumors

Raman spectroscopy provides excellent specificity for in vivo preclinical imaging through a readout of fingerprint-like spectra. To achieve sufficient sensitivity for in vivo Raman imaging, metallic gold nanoparticles larger than 10 nm were employed to amplify Raman signals via surface-enhanced Raman scattering (SERS). However, the inability to excrete such large gold nanoparticles has restricted the translation of Raman imaging. Here we present Raman-active metallic gold supraclusters that are biodegradable and excretable as nanoclusters. Although the small size of the gold nanocluster building blocks compromises the electromagnetic field enhancement effect, the supraclusters exhibit bright and prominent Raman scattering comparable to that of large gold nanoparticle-based SERS nanotags due to high loading of NIR-resonant Raman dyes and much suppressed fluorescence background by metallic supraclusters. The bright Raman scattering of the supraclusters was pH-responsive, and we successfully performed in vivo Raman imaging of acidic tumors in mice. Furthermore, in contrast to large gold nanoparticles that remain in the liver and spleen, the supraclusters dissociated into small nanoclusters, and 73% of the administered dose to mice was excreted over 4 months. The highly excretable Raman supraclusters demonstrated here offer great potential for clinical applications of in vivo Raman imaging by replacing non-excretable large gold nanoparticles.

bioengineering↗