Viral docking and maturation in whole bacterial cells at near atomic resolution and in 4 dimensions

Lead Research Organisation: John Innes Centre
Department Name: Contracts Office


Host-pathogen relationships are complex, dynamic and still poorly understood. No high-resolution structural information of intact host cells infected by a pathogen has been generated in four dimensions (4D) and our quantitative understanding of the underlying molecular interactions is limited. Here, we will use Caulobacter crescentus cells infected with a virus (bacteriophage fCb13) as a simple model system to investigate the structural, genetic and kinetic basis of host-pathogen relationships in 4D by electron cryo-tomography (ECT), fluorescence microscopy (FM), genetics and mathematical modeling.
The many conceptual similarities in the organization and function of prokaryotic and eukaryotic cells, lead us to hypothesize that bacteriophages, akin to eukaryotic viruses, interact with their host i) through >1 one host surface docking site (“receptor/co-receptor”), ii) at a discrete positions at the cell surface, iii) at a precise time point in the cell cycle and iv) through internal cytoskeletal structures to produce progeny. Our three-member team has targeted C. crescentus and its phage fCb13 as a host-pathogen model system. Relying on our three areas of expertise - Caulobacter genetics and fluorescence microscopy (Viollier), whole cell ECT and image processing (Wright), and mathematical modeling (Howard) – we will dissect in vitro and in situ
1) the multi-factorial nature of fCb13 infection (adsorption/adhesion/genome injection) in WT and mutants,
2) the influence of the bacterial cell-cycle and cytoskeleton on fCb13 progeny production.
These cytological, genetic and quantitative studies will not only shed light on the details of fCb13 infection and progeny production specific to C. crescentus and related host-pathogen systems, but also provide conceptual insights into conserved biological principles like attachment, spatio-temporal organization and energetic coupling of (sub)cellular processes.


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Description We discovered the minimal components required to regulate the asymmetric cell cycle of Caulobacter crescentus, where a single Caulobacter cell divides into two distinct daughter cells with different developmental programs. This research overturned the existing paradigms in the field, in particular demonstrating that cell cycle components that were believed to be essential were in fact dispensable. Our methodology of developing a minimal mathematical model for the system was also novel and should find wide applications in cell cycle studies.
Exploitation Route One way would be to use our understanding of the Caulobacter cell cycle to examine how it is corrupted by phages (viruses that infect bacteria). This would enable fundamental understanding, in a relatively simple system, of how viruses perturb cell cycle dynamics for their own benefit.
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology

Description Our findings related to fundamental microbiology and how to understand cell cycle dynamics through a minimal mathematical modelling and experimental approach. This should enable a deeper and more rapid understanding of how many other cells control their cell cycle. However, this understanding will take time to feed into more practical applications, which will, we hope, appear but on longer time horizons of 5-10 years.
Description MH+PV 
Organisation University of Geneva
Country Switzerland 
Sector Academic/University 
PI Contribution Mathematical modelling of the asymmetric Caulobacter crescentus cell cycle.
Collaborator Contribution Experimental genetic and imaging approaches to Caulobacter.
Impact Multi-disciplinary: experimental microbiology together with mathematical modelling
Start Year 2010