Biology subjects

Eshraghi, A.

Publications and source records attributed to Eshraghi, A..

5 recordsLinked to original sources

bioRxiv2026

High-Throughput Profiling of Bacterial Respiration Using the Resipher Reveals Functional Responses to Nutrients and Antibiotics

Oxygen consumption is a direct functional readout of bacterial respiration and metabolic state, yet existing methods for quantifying oxygen dynamics are limited in throughput and temporal resolution. Here, we establish a high-throughput platform for real-time profiling of bacterial respiration by adapting the Resipher, a non-invasive oxygen quantification system, for use in bacterial cultures. Measurements obtained with the Resipher were comparable to those generated using a Clark-type electrode-based high-resolution respirometer, validating its quantitative accuracy. Across Gram-negative (Escherichia coli, Francisella novicida) and Gram-positive (Enterococcus faecalis, Staphylococcus aureus) species, the Resipher generated reproducible measurements under both growth-permissive and growth-limited conditions, enabling assessment of respiration, independent of proliferation. Functional profiling revealed that oxygen consumption responds dynamically to nutrient availability and electron transport chain perturbation, including species-specific inhibition by benzarone. Notably, oxygen consumption profiles distinguished bactericidal and bacteriostatic antibiotics, with bactericidal agents transiently increasing respiration and bacteriostatic agents suppressing metabolic activity. Together, these findings establish oxygen consumption as a sensitive physiological readout and highlight the potential utility of respiratory profiling for mechanistic studies.

microbiology↗

bioRxiv2026

Selective inhibition of respiratory complex I reveals a bioenergetic vulnerability in Francisella

F. tularensis is a highly infectious Gram-negative bacterial pathogen that causes tularemia, a re-emerging zoonosis of public health concern. Here we identify respiratory complex I as a selective vulnerability in Francisella and define the mechanism of action of a pyrazole compound, tolfenpyrad, with species-specific antibacterial activity. Using F. novicida as a surrogate model, we demonstrated that tolfenpyrad selectively inhibits growth with no measurable effect on E. coli or P. aeruginosa. Tolfenpyrad rapidly suppressed oxygen consumption, depleted ATP, collapsed proton motive force, and induced reactive oxygen species, indicating disruption of bacterial metabolism. Biochemical assays demonstrated selective inhibition of NADH-dependent respiration and membrane-associated NADH oxidation, whereas succinate-driven respiration was unaffected. Moreover, the alternative NADH dehydrogenase (ndh) was not required for tolfenpyrad activity. Structural docking identified a potential tolfenpyrad-binding pocket within the membrane subunit NuoM. These findings reveal species-specific inhibition of Francisella complex I and establish respiratory metabolism as a promising antimicrobial target in these bacteria.

microbiology↗

bioRxiv2026

Sustained Improvements in Student Outcomes Following Integration of Clinical Case Narratives in Veterinary Microbiology Curriculum

Microbiology education in veterinary curricula requires students to integrate complex foundational knowledge with clinical application, yet traditional lecture-based approaches often emphasize memorization over higher-order reasoning. In this study, we evaluated the impact of integrating clinically oriented, case-based instruction into a veterinary microbiology course within a Doctor of Veterinary Medicine curriculum. Using a quasi-experimental, multi-year design, student outcomes were compared before (2019, 2021) and after (2022-2025) implementation of case-based teaching while maintaining consistent course content, structure, and assessments. Introduction of clinical case examples was associated with significant and sustained improvements in student evaluations across multiple domains, including perceived relevance, critical thinking, and overall course value. Instructor-related evaluation metrics also improved. Student performance, measured by final course grades, increased following the intervention without evidence of grade inflation. These findings demonstrate that integrating clinically relevant case narratives into microbiology instruction enhances student engagement and student performance. This work highlights a practical and scalable strategy for improving microbiology education, particularly within veterinary and other health-professions curricula.

scientific communication and education↗

bioRxiv2025

Targeting deubiquitinating enzymes (DUBs) and ubiquitin pathway modulators to enhance host defense against bacterial infections

The rise of antibiotic-resistant bacterial pathogens poses a critical global health challenge, necessitating innovative therapeutic approaches. This study explores host-targeted therapies (HTTs) by focusing on deubiquitinating enzymes (DUBs), essential modulators of the ubiquitin-proteasome system (UPS) that regulate host-pathogen interactions during many bacterial infections. Using Salmonella-infected macrophages as a model, we identified UPS modulators that enhance bacterial clearance and observed significant changes in DUB expression, particularly USP25, USP46, and Otud7b. The small-molecule DUB inhibitor AZ-1 significantly reduced intracellular bacterial loads in vitro and mitigated early disease severity in a murine model by decreasing fecal bacterial loads and preserving host weight. However, AZ-1 alone did not achieve complete clearance of Salmonella and required combination with extracellular-targeting antibiotics for optimal efficacy. Notably, AZ-1 demonstrated broad-spectrum activity against multidrug-resistant pathogens, including Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Transcriptomic analyses revealed infection-induced DUB regulation and highlighted pathways modulating immune responses, including TNF- secretion. These findings highlight the potential of targeting the UPS as a host-directed antimicrobial strategy and provide a foundation for developing innovative therapies to combat antimicrobial resistance.

microbiology↗

bioRxiv2024

Pathogenicity determinant protein E is a Francisella type VI secretion system effector protein that modulates host death

Francisella tularensis is a highly pathogenic Gram-negative intracellular bacterial pathogen and the etiologic agent of tularemia, a fatal zoonotic disease that poses a threat to global public health. F. tularensis virulence is mediated by genes on the Francisella pathogenicity island (FPI), which encodes a unique contractile secretion apparatus with functional and structural similarity to bacterial type VI secretion systems (T6SSs). T6SSs can inject effector proteins into host cells to facilitate invasion, intracellular proliferation, and pathogenesis; however, the identity and function of Francisella effectors are still unclear. In this study, we measured T6SS activity in a series of FPI deletion mutants to identify genes that are required for core apparatus activity. We found that Pathogenicity Determinant Protein E (PdpE) is not required for secretion of T6SS substrates or intramacrophage growth. Instead, PdpE forms a complex with another T6SS-secreted effector, PdpC, and limits death of infected host cells by attenuating the macrophage type I interferon response. Importantly, a {Delta}pdpE mutant more rapidly induces death in an established invertebrate in vivo model for Francisella infection. These data define the role of a previously uncharacterized substrate of the Francisella T6SS and provide new insights into host-Francisella interaction.

microbiology↗