title: Yersinia enterocolitica type III secretion injectisomes form regularly spaced clusters, which incorporate new machines upon activation.
abstract: Bacterial type III secretion systems or injectisomes are multiprotein complexes directly transporting bacterial effector proteins into eukaryotic host cells. To investigate the distribution of injectisomes in the bacterium and the influence of activation of the system on that distribution, we combined in vivo fluorescent imaging and high-resolution in situ visualization of Yersinia enterocolitica injectisomes by cryo-electron tomography. Fluorescence microscopy showed the injectisomes as regularly distributed spots around the bacterial cell. Under secreting conditions (absence of Ca(2+) ), the intensity of single spots significantly increased compared with non-secreting conditions (presence of Ca(2+) ), in line with an overall up-regulation of expression levels of all components. Single injectisomes observed by cryo-electron tomography tended to cluster at distances less than 100 nm, suggesting that the observed fluorescent spots correspond to evenly distributed clusters of injectisomes, rather than single injectisomes. The up-regulation of injectisome components led to an increase in the number of injectisomes per cluster rather than the formation of new clusters. We suggest that injectisome clustering may allow more effective secretion into the host cells.
authors.affiliation: Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University Basel, WRO-1058, Mattenstrasse 26, Basel, 4058, Switzerland; Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, 4056, Switzerland.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Kudryashev
authors.forename: Andreas
authors.initials: A
authors.lastname: Diepold
authors.forename: Marlise
authors.initials: M
authors.lastname: Amstutz
authors.forename: Judith P
authors.initials: JP
authors.lastname: Armitage
authors.forename: Henning
authors.initials: H
authors.lastname: Stahlberg
authors.forename: Guy R
authors.initials: GR
authors.lastname: Cornelis
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000235:genetics; D001692:Biological Transport; D055032:Electron Microscope Tomography; D008856:Microscopy, Fluorescence; D015854:Up-Regulation; D015008:Yersinia enterocolitica / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems