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Proc Natl Acad Sci U S A. 2014 Sep 16;111(37):E3910-8. doi: 10.1073/pnas.1414944111. Epub 2014 Sep 2.

Xylella fastidiosa outer membrane vesicles modulate plant colonization by blocking attachment to surfaces.

Author information

1
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and.
2
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, SP 05508-000, São Paulo, Brazil.
3
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and icelab@berkeley.edu.

Abstract

Outer membrane vesicles (OMVs) of Gram-negative bacteria have been studied intensively in recent years, primarily in their role in delivering virulence factors and antigens during pathogenesis. However, the near ubiquity of their production suggests that they may play other roles, such as responding to envelope stress or trafficking various cargoes to prevent dilution or degradation by other bacterial species. Here we show that OMVs produced by Xylella fastidiosa, a xylem-colonizing plant pathogenic bacterium, block its interaction with various surfaces such as the walls of xylem vessels in host plants. The release of OMVs was suppressed by the diffusible signal factor-dependent quorum-sensing system, and a X. fastidiosa ΔrpfF mutant in which quorum signaling was disrupted was both much more virulent to plants and less adhesive to glass and plant surfaces than the WT strain. The higher virulence of the ΔrpfF mutant was associated with fivefold higher numbers of OMVs recovered from xylem sap of infected plants. The frequency of attachment of X. fastidiosa to xylem vessels was 20-fold lower in the presence of OMVs than in their absence. OMV production thus is a strategy used by X. fastidiosa cells to adjust attachment to surfaces in its transition from adhesive cells capable of insect transmission to an "exploratory" lifestyle for systemic spread within the plant host which would be hindered by attachment. OMV production may contribute to the movement of other bacteria in porous environments by similarly reducing their contact with environmental constituents.

KEYWORDS:

Pierce disease; XadA; antiadhesiveness; phytopathogen

PMID:
25197068
PMCID:
PMC4169949
DOI:
10.1073/pnas.1414944111
[Indexed for MEDLINE]
Free PMC Article

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