title: Upstream migration of Xylella fastidiosa via pilus-driven twitching motility.
abstract: Xylella fastidiosa is a xylem-limited nonflagellated bacterium that causes economically important diseases of plants by developing biofilms that block xylem sap flow. How the bacterium is translocated downward in the host plant's vascular system against the direction of the transpiration stream has long been a puzzling phenomenon. Using microfabricated chambers designed to mimic some of the features of xylem vessels, we discovered that X. fastidiosa migrates via type IV-pilus-mediated twitching motility at speeds up to 5 mum min(-1) against a rapidly flowing medium (20,000 mum min(-1)). Electron microscopy revealed that there are two length classes of pili, long type IV pili (1.0 to 5.8 mum) and short type I pili (0.4 to 1.0 mum). We further demonstrated that two knockout mutants (pilB and pilQ mutants) that are deficient in type IV pili do not twitch and are inhibited from colonizing upstream vascular regions in planta. In addition, mutants with insertions in pilB or pilQ (possessing type I pili only) express enhanced biofilm formation, whereas a mutant with an insertion in fimA (possessing only type IV pili) is biofilm deficient.
authors.affiliation: Department of Plant Pathology, Cornell University-New York State Agricultural Experiment Station, Geneva, NY 14456, USA.
authors.forename: Yizhi
authors.initials: Y
authors.lastname: Meng
authors.forename: Yaxin
authors.initials: Y
authors.lastname: Li
authors.forename: Cheryl D
authors.initials: CD
authors.lastname: Galvani
authors.forename: Guixia
authors.initials: G
authors.lastname: Hao
authors.forename: James N
authors.initials: JN
authors.lastname: Turner
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Burr
authors.forename: H C
authors.initials: HC
authors.lastname: Hoch
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms; D036781:Fimbriae Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000502:physiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009068:Movement; D016296:Mutagenesis; D010088:Oxidoreductases / Q000235:genetics; D010935:Plant Diseases / Q000382:microbiology*; D027843:Vitis / Q000382:microbiology* / Q000648:ultrastructure; D044167:Xylella / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; C063055:fimbrillin; C084295:pilQ protein, bacteria; D036781:Fimbriae Proteins; D010088:Oxidoreductases; C068255:pilB protein, Bacteria