Biophysics Seminar 2 TT3
Venue change - Physics Beecroft Building, Simpkins Lee Seminar Room
Talk 1: DNA reactions for successful plasmid conjugation
Dr Yoshiharu Yamaichi, CNRS Group Leader, I2BC Institute of Université Paris-Saclay
Bacterial conjugation is a major horizontal gene transfer mechanism through which DNA is transferred from a donor to a recipient bacterium by direct cell-to-cell contact, being a major driving force of bacterial genome evolution and the dissemination of metabolic properties, such as resistance to antibiotics.
Even though conjugation is known since 1940s, and has been extensively studied using a variety of approaches, our recent results highlighted we still have some important knowledge gaps in the events occurring within the recipient cell between DNA entry and the establishment of exconjugant cell.
Briefly, pESBL, a multidrug resistant conjugative plasmid isolated from E. coli O104 outbreak strain, encodes a very atypical DNA methyltransferase, M.EcoGIX. It methylates adenine residues without specific recognition sequence but only one strand of the double-stranded (ds) DNA. We first showed that M.EcoGIX counteracts host restriction mechanism, involving successful establishment of the plasmid in a new host cell. Follow-up study on the mode of function of M.EcoGIX suggested that DNA methylation likely happens inside the recipient cell, instead of transferring single-stranded (ss)DNA already methylated in the donor cell. In this scenario, gene expression and function (DNA methylation) precede the recognition of the target dsDNA by restriction enzyme in the recipient cell, suggesting a surprising temporal cascade of DNA reactions.
Furthermore, our genome-wide approach unveiled that host-encoded UvrD helicase plays important role for successful conjugative transfer. Study on UvrD function during conjugation proposed a model that in the recipient cell, host single strand binding proteins and RecA bind to the ssDNA upon its entry. RecA filament formation on ssDNA can disturb hairpin formation, which is shown to be important for transcription and dsDNA synthesis. UvrD removes RecA from ssDNA, allowing to reconstitute hairpin and dsDNA synthesis and so on.
Talk 2: How to detect viruses in under 5min
Nicolas Shiaelis, Kapanidis Group, Biophysics & Kavli Institute for Nanoscience Discovery (Oxford)
The ongoing surge in viral outbreaks, highlighted by the COVID-19 pandemic, underscores the critical need for quick and accurate viral diagnostics. We introduce an innovative virus detection method combining fluorescence microscopy and convolutional neural networks, capable of identifying viruses directly from clinical samples in under five minutes without the need for sample purification or amplification. This technique distinguishes between various viruses and strains, including SARS-CoV-2 and influenza, demonstrating a 98% accuracy rate in clinical evaluations. The platform’s design allows for seamless updates to include new pathogens, offering a scalable solution for future outbreak surveillance and response.
Date:
10 May 2024, 10:00 (Friday, 3rd week, Trinity 2024)
Venue:
Beecroft Building
Venue Details:
Simpkins Lee Seminar Room
Speakers:
Dr Yoshiharu Yamaichi (I2BC, Paris-Saclay University),
Nicolas Shiaelis (University of Oxford)
Organisers:
Dr Jagadish Prasad Hazra (Biophysics, University of Oxford),
Dr Stelios Chatzimichail (Biophysics, University of Oxford),
Emma Lalande (Biophysics, University of Oxford)
Part of:
Biophysics Seminar Series 2023-2024
Booking required?:
Not required
Audience:
Members of the University only
Editor:
Emma Lalande
