title: Cell cycle constraints on capsulation and bacteriophage susceptibility.
abstract: Despite the crucial role of bacterial capsules in pathogenesis, it is still unknown if systemic cues such as the cell cycle can control capsule biogenesis. In this study, we show that the capsule of the synchronizable model bacterium Caulobacter crescentus is cell cycle regulated and we unearth a bacterial transglutaminase homolog, HvyA, as restriction factor that prevents capsulation in G1-phase cells. This capsule protects cells from infection by a generalized transducing Caulobacter phage (φCr30), and the loss of HvyA confers insensitivity towards φCr30. Control of capsulation during the cell cycle could serve as a simple means to prevent steric hindrance of flagellar motility or to ensure that phage-mediated genetic exchange happens before the onset of DNA replication. Moreover, the multi-layered regulatory circuitry directing HvyA expression to G1-phase is conserved during evolution, and HvyA orthologues from related Sinorhizobia can prevent capsulation in Caulobacter, indicating that alpha-proteobacteria have retained HvyA activity.
authors.affiliation: Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ardissone
authors.affiliation: Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.
authors.forename: Coralie
authors.initials: C
authors.lastname: Fumeaux
authors.affiliation: Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Bergé
authors.affiliation: Institute of Life Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Audrey
authors.initials: A
authors.lastname: Beaussart
authors.affiliation: Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.
authors.forename: Laurence
authors.initials: L
authors.lastname: Théraulaz
authors.affiliation: Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.
authors.forename: Sunish Kumar
authors.initials: SK
authors.lastname: Radhakrishnan
authors.affiliation: Institute of Life Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
authors.affiliation: Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva, University of Geneva, Geneva, Switzerland.
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Viollier
mesh_terms: D020561:Alphaproteobacteria; D016667:Bacterial Capsules / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001435:Bacteriophages / Q000502:physiology*; D016934:Caulobacter / Q000166:cytology* / Q000201:enzymology / Q000648:ultrastructure / Q000821:virology*; D002453:Cell Cycle; D005453:Fluorescence; D016193:G1 Phase; D015964:Gene Expression Regulation, Bacterial; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D055550:Protein Stability; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D011503:Transglutaminases / Q000378:metabolism; D014297:Trimethylsilyl Compounds / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D014297:Trimethylsilyl Compounds; D011503:Transglutaminases
keywords: BTLCP; Caulobacter crescentus; E. coli; bacteriophage; capsule; cell cycle; generalized transduction; infectious disease; microbiology