Optimized Fluorescence Complementation Platform for Visualizing Salmonella Effector Proteins Reveals Distinctly Different Intracellular Niches in Different Cell Types

ACS Infect Dis. 2017 Aug 11;3(8):575-584. doi: 10.1021/acsinfecdis.7b00052. Epub 2017 Jun 9.


The bacterial pathogen Salmonella uses sophisticated type III secretion systems (T3SS) to translocate and deliver bacterial effector proteins into host cells to establish infection. Monitoring these important virulence determinants in the context of live infections is a key step in defining the dynamic interface between the host and pathogen. Here, we provide a modular labeling platform based on fluorescence complementation with split-GFP that permits facile tagging of new Salmonella effector proteins. We demonstrate enhancement of split-GFP complementation signals by manipulating the promoter or by multimerizing the fluorescent tag and visualize three effector proteins, SseF, SseG, and SlrP, that have never before been visualized over time during infection of live cells. Using this platform, we developed a methodology for visualizing effector proteins in primary macrophage cells for the first time and reveal distinct differences in the effector-defined intracellular niche between primary macrophage and commonly used HeLa and RAW cell lines.

Keywords: Salmonella; bacterial effector proteins; host−pathogen interface; live cell imaging; split-GFP.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Cell Line
  • Gene Expression
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Host Specificity
  • Host-Pathogen Interactions*
  • Humans
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Macrophages / metabolism
  • Macrophages / microbiology*
  • Mice
  • Optical Imaging
  • Primary Cell Culture
  • Protein Transport
  • Salmonella typhimurium / genetics*
  • Salmonella typhimurium / growth & development
  • Salmonella typhimurium / pathogenicity
  • Staining and Labeling / methods
  • Type III Secretion Systems / genetics
  • Type III Secretion Systems / metabolism
  • Virulence Factors / genetics*
  • Virulence Factors / metabolism


  • Bacterial Proteins
  • Luminescent Proteins
  • SlrP protein, Salmonella typhimurium
  • SseG protein, Salmonella typhimurium
  • Type III Secretion Systems
  • Virulence Factors
  • red fluorescent protein
  • Green Fluorescent Proteins