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Updated: Apr 16, 2026

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Lipopolysaccharide surface structure does not influence IcsA polarity.

Matthew Thomas Doyle1, Marcin Grabowicz2, Kerrie Leanne May2

  • 1Department of Molecular and Cellular Biology, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.

FEMS Microbiology Letters
|March 18, 2015
PubMed
Summary

Shigella bacteria use actin-based motility for gut invasion. This study refutes models of asymmetric O-antigen masking and membrane diffusion, supporting symmetric masking of the IcsA protein for proper bacterial movement.

Keywords:
Shigellaautotransporterbacterial polelipopolysaccharideminicellouter membrane

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Area of Science:

  • Microbiology
  • Cell Biology
  • Bacterial Pathogenesis

Background:

  • Shigella species cause bacillary dysentery by invading host cells.
  • Actin-based motility, initiated by the IcsA protein, is crucial for Shigella spread within the gut.
  • Lipopolysaccharide (LPS) O-antigen has been proposed to regulate IcsA positioning for efficient motility.

Purpose of the Study:

  • To investigate the role of LPS O-antigen chain length and distribution in maintaining IcsA polarity.
  • To test proposed models of asymmetric O-antigen masking and membrane fluidity restriction on IcsA positioning.
  • To elucidate the precise mechanism by which O-antigen influences IcsA surface distribution.

Main Methods:

  • Utilized bacterial minicells for controlled study of surface protein localization.
  • Employed quantitative microscopy techniques to analyze IcsA distribution.
  • Compared wild-type Shigella strains with O-antigen deficient strains.

Main Results:

  • Data refutes models suggesting asymmetric O-antigen masking of IcsA.
  • Evidence contradicts the hypothesis that LPS O-antigen restricts IcsA diffusion by altering membrane fluidity.
  • Findings support a model of symmetric O-antigen masking of IcsA.
  • Demonstrated equivalent IcsA surface distribution between wild-type and O-antigen deficient strains.

Conclusions:

  • Previous conclusions on IcsA polarity regulation may have been confounded by variations in total cellular IcsA levels.
  • Symmetric masking by O-antigen, rather than asymmetric masking or membrane diffusion effects, is the likely mechanism influencing IcsA localization.
  • This study refines the understanding of bacterial motility and host cell invasion mechanisms in Shigella.