title: Visualization of the Serratia Type VI Secretion System Reveals Unprovoked Attacks and Dynamic Assembly.
abstract: The Type VI secretion system (T6SS) is a bacterial nanomachine that fires toxic proteins into target cells. Deployment of the T6SS represents an efficient and widespread means by which bacteria attack competitors or interact with host organisms and may be triggered by contact from an attacking neighbor cell as a defensive strategy. Here, we use the opportunist pathogen Serratia marcescens and functional fluorescent fusions of key components of the T6SS to observe different subassemblies of the machinery simultaneously and on multiple timescales in vivo. We report that the localization and dynamic behavior of each of the components examined is distinct, revealing a multi-stage and dynamic assembly process for the T6SS machinery. We also show that the T6SS can assemble and fire without needing a cell contact trigger, defining an aggressive strategy that broadens target range and suggesting that activation of the T6SS is tailored to survival in specific niches.
authors.affiliation: Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Gerc
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: Andreas
authors.initials: A
authors.lastname: Diepold
authors.affiliation: Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: Katharina
authors.initials: K
authors.lastname: Trunk
authors.affiliation: Centre of Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Porter
authors.affiliation: Edinburgh Super-Resolution Imaging Consortium, www.esric.org, and Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University, Edinburgh EH14 4AS, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Rickman
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: Judith P
authors.initials: JP
authors.lastname: Armitage
authors.affiliation: Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: Nicola R
authors.initials: NR
authors.lastname: Stanley-Wall
authors.affiliation: Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK. Electronic address: s.j.coulthurst@dundee.ac.uk.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Coulthurst
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D005810:Multigene Family; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012706:Serratia marcescens / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D000069376:Type VI Secretion Systems / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D000097573:Red Fluorescent Protein
chemical_list: D001426:Bacterial Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D000069376:Type VI Secretion Systems; D000097573:Red Fluorescent Protein