Gene expression Reprogramming in the new host cell during bacterial conjugation by the YfjB plasmid-encoded factor – GRAB

Bacterial DNA conjugation is a widespread horizontal gene transfer mechanism responsible for the intra- and inter-species dissemination of various metabolic properties and accounts for 80% of acquired resistance in bacteria. Due to its fundamental and clinical importance, conjugation has been extensively studied, and we now have a detailed understanding of the molecular events that occur in the donor cell before transfer. However, despite decades of investigation, we still do not know what is the impact of plasmid entry in the new host cell or how plasmid-encoded factors facilitate the establishment of the plasmid and the development of associated biological functions. Answering these questions is essential to understand how a bacterium that receives exogenous DNA by conjugation becomes virulent or resistant to heavy metals or antimicrobials, and also able to further disseminate these functions in the bacterial community.
The consortium has identified a new plasmid-encoded factor, the YjfB protein, that reprograms gene expression in the new host cell after plasmid acquisition. The consortium showed that YfjB is produced immediately upon plasmid entry and forms intense and dynamic foci associated with the chromosome DNA in vivo. YfjB contains four domains: domains I and II are homologous to ParB-family proteins, while domains III and IV do not show a resemblance to any known protein. In vitro biochemical analysis showed that YfjB binds to the double-stranded DNA and forms dimers in solution. CryoEM data revealed that YfjB dimers are formed by a “dome” consisting of a dimer of domain IV, and two protruding “legs” adopting various conformations.
The GRAB research program will characterise the molecular structure and biological function of YfjB using an original and straightforward multidisciplinary framework that combines genetics, live-cell imaging, and biochemical and structural approaches. The bottom-line concepts of the GRAB project are unique to our consortium. Specific strengths of the proposal are (i) the originality and novelty of the topic; (ii) a clear working hypothesis that builds from solid preliminary data obtained within the consortium; (iii) high complementarity between the two teams that stand at the forefront of microbiology research; (iv) Interdisciplinary approach and straightforward experimental plan; (v) The availability of experimental tools and equipment.
Expected results will provide new insights helping to understand how a bacterium that receives exogenous DNA becomes resistant to antimicrobials and is capable of disseminating these functions in the bacterial community. This project will also extend our knowledge of the widespread ParB-family proteins and their diversity of functions in bacteria. This project fits with the Axis C.3 priority of the ANR call (CES12) and is in line with the WHO priority research recommendations.