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1.
Cell Microbiol ; 10(4): 958-84, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18031307

ABSTRACT

The biogenesis of the Salmonella-containing vacuole within mammalian cells has been intensively studied over recent years. However, the ability of Salmonella to sense and adapt to the intracellular environment of different types of host cells has received much less attention. To address this issue, we report the transcriptome of Salmonella enterica serovar Typhimurium SL1344 within epithelial cells and show comparisons with Salmonella gene expression inside macrophages. We report that S. Typhimurium expresses a characteristic intracellular transcriptomic signature in response to the environments it encounters within different cell types. The signature involves the upregulation of the mgtBC, pstACS and iro genes for magnesium, phosphate and iron uptake, and Salmonella pathogenicity island 2 (SPI2). Surprisingly, in addition to SPI2, the invasion-associated SPI1 pathogenicity island and the genes involved in flagellar biosynthesis were expressed inside epithelial cells at later stages of the infection, while they were constantly downregulated in macrophage-like cells. To our knowledge, this is the first report of the simultaneous transcription of all three Type Three Secretion Systems (T3SS) within an intracellular Salmonella population. We discovered that S. Typhimurium strain SL1344 was strongly cytotoxic to epithelial cells after 6 h of infection and hypothesize that the time-dependent changes in Salmonella gene expression within epithelial cells reflects the bacterial response to host cells that have been injured by the infection process.


Subject(s)
Epithelial Cells/microbiology , Salmonella typhimurium/growth & development , Salmonella typhimurium/genetics , Transcription, Genetic , Animals , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Caco-2 Cells , Cell Line , Epithelial Cells/cytology , Epithelial Cells/metabolism , Gene Expression Regulation, Bacterial , Genes, Bacterial/genetics , HeLa Cells , Humans , Immunohistochemistry , Macrophages/cytology , Macrophages/metabolism , Macrophages/microbiology , Microscopy, Electron, Transmission , Microscopy, Fluorescence , Oligonucleotide Array Sequence Analysis , Reverse Transcriptase Polymerase Chain Reaction , Salmonella typhimurium/ultrastructure
2.
J Microsc ; 218(Pt 1): 46-51, 2005 Apr.
Article in English | MEDLINE | ID: mdl-15817062

ABSTRACT

IcsA is an autotransporter protein that plays a role in the virulence of Shigella bacteria. We have examined the cellular localization of a fusion of an IcsA fragment to the green fluorescent protein (GFP) expressed in Escherichia coli using a dual epifluorescence and scanning near-field optical microscope. By combining the data obtained from far-field with near-field microscopy of the same sample, discrimination between surface-bound fusion proteins and fusion proteins located in the cellular cytoplasm becomes possible. Furthermore, and for the first time, the inherent advantages in resolution of the near-field images provides highly specific details of the location of a GFP fusion protein on a bacterial cell surface.


Subject(s)
Bacterial Proteins/metabolism , DNA-Binding Proteins/metabolism , Microscopy, Fluorescence/methods , Microscopy, Scanning Probe/methods , Transcription Factors/metabolism , Bacterial Proteins/genetics , DNA-Binding Proteins/genetics , Escherichia coli/genetics , Escherichia coli/metabolism , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Microscopy, Atomic Force , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Shigella/genetics , Transcription Factors/genetics
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