Biology subjects

Sargison, F. A.

Publications and source records attributed to Sargison, F. A..

3 recordsLinked to original sources

bioRxiv2026

Single-molecule imaging of DNA repair and cytoplasmic rigidification in intracellular bacteria

DNA damage is an important component of the antibacterial response of phagocytes, but which DNA repair mechanisms are active in intracellular bacteria remains unclear. We developed a live-cell single-molecule tracking approach to directly measure DNA repair activity in Escherichia coli within macrophages. Phagocytosis activates bacterial base excision and nucleotide excision repair pathways and increases DNA mismatch repair foci indicative of DNA replication errors. Phagocyte-generated stresses also cause a general slowdown in protein diffusion within bacteria, consistent with a transition of the cytoplasm towards a glass-like state, which is associated with reduced metabolic activity. At the single-cell level, DNA repair activity is highly heterogeneous, with metabolically inactive bacteria showing the greatest engagement of repair proteins. Together, these findings reveal how distinct DNA repair pathways are deployed during macrophage infection and link repair activity to the metabolic and biophysical states of individual intracellular bacteria.

microbiology↗

bioRxiv2023

Time-lapse mesoscopy of Candida albicans and Staphylococcus aureus dual-species biofilms reveals a structural role for the hyphae of C. albicans in biofilm formation

Polymicrobial infection with Candida albicans and Staphylococcus aureus may result in a concomitant increase in virulence and resistance to antimicrobial drugs. This enhanced pathogenicity phenotype is mediated by numerous factors including metabolic processes and direct interaction of S. aureus with C. albicans hyphae. The overall structure of biofilms is known to contribute to their recalcitrance to treatment, however the dynamics of direct interaction between species and how it contributes to pathogenicity is poorly understood. To address this, a novel time-lapse mesoscopic optical imaging method was developed to enable the formation of C. albicans/S. aureus whole dual-species biofilms to be followed. It was found that yeast-form or hyphal-form C. albicans in the biofilm founder-population profoundly affects the structure of the biofilm as it matures. Different sub-populations of C. albicans and S. aureus arise within each biofilm as a result of the different C. albicans morphotypes, resulting in distinct sub-regions. These data reveal that C. albicans cell morphology is pivotal in the development of global biofilm architecture and the emergence of colony macrostructures and may temporally influence synergy in infection.

microbiology↗

bioRxiv2022

Nanoscaled discovery of a shunt rifamycin from Salinispora arenicola using a three-colour GFP-tagged Staphylococcus aureus macrophage infection assay.

Antimicrobial resistance has emerged as an urgent global public health threat, and development of novel therapeutics for treating infections caused by multi-drug resistant bacteria is urgent. Staphylococcus aureus is a major human and animal pathogen, responsible for high levels of morbidity and mortality worldwide. The intracellular survival of S. aureus in macrophages contributes to immune evasion, dissemination, and resilience to antibiotic treatment. Here, we present a confocal fluorescence imaging assay for monitoring macrophage infection by GFP-tagged Staphylococcus aureus as a front-line tool to identify antibiotic leads. The assay was employed in combination with nanoscaled chemical analyses to facilitate the discovery of a novel, active rifamycin analogue. Our findings indicate a promising new approach to the identification of anti-microbial compounds with macrophage intracellular activity. The novel antibiotic identified here may represent a useful addition to our armoury in tackling the silent pandemic of antimicrobial resistance.

cell biology↗