Selective Capture of<i>Salmonella enterica</i>Serovar Typhi Genes Expressed in Macrophages That Are Absent from the<i>Salmonella enterica</i>Serovar Typhimurium Genome

Faucher, Sébastien P.; Curtiss, Roy

doi:10.1128/iai.73.8.5217-5221.2005

Cited by 36 publications

(24 citation statements)

References 33 publications

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“…In typhoid fever patients, antibodies to three fimbrial systems, Tcf, Stb, and Csg, were detected (10). Nevertheless, we have previously detected the stgCЈ transcript during infection of macrophages (6). The optimal conditions for expression of Stg may not have been found yet, and we need to further investigate its regulation, but our results are consistent with the hypothesis that the stg fimbrial operon may be important for the initial interaction with host cells.…”

Section: Discussionsupporting

confidence: 78%

“…Serovar Typhi is restricted to humans and harbors 13 putative fimbrial systems and a type IV pilus (29). We have previously found that stg is transcribed by serovar Typhi within macrophages (6). In S. enterica, the stg fimbrial cluster located in the glmS-pstS region is present only in serovar Typhi (30).…”

Section: Discussionmentioning

confidence: 99%

“…Five of these operons, sef, sta, ste, stg, and tcf, and the type IV pili were not detected in serovar Typhimurium (29). In a previous study, we determined that STY3920 (stgC), a gene encoding the usher of the putative stg fimbrial operon, is absent in serovar Typhimurium and is expressed by serovar Typhi during infection of human macrophages (6). stgC contains a premature stop codon that disrupts the predicted open reading frame (ORF) encoding the usher, and it is therefore considered a pseudogene.…”

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confidence: 99%

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Contribution of thestgFimbrial Operon ofSalmonella entericaSerovar Typhi during Interaction with Human Cells

et al. 2007

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Salmonella serovars contain a wide variety of putative fimbrial systems that may contribute to colonization of specific niches. Salmonella enterica serovar Typhi is the etiologic agent of typhoid fever and is a pathogen specific to humans. In a previous study, we identified a gene, STY3920 (stgC), encoding the predicted usher of the stg fimbrial operon, that was expressed by serovar Typhi during infection of human macrophages. The stg genes are located in the glmS-pstS intergenic region in serovar Typhi and certain Escherichia coli strains, but they are absent in other S. enterica serovars. We cloned the stg fimbrial operon into a nonfimbriate E. coli K-12 strain and into S. enterica serovar Typhimurium. We demonstrated that the stg fimbrial operon contributed to increased adherence to human epithelial cells. Transcriptional fusion assays with serovar Typhi suggested that stg is preferentially expressed in minimal medium. Deletion of stg reduced adherence of serovar Typhi to epithelial cells. However, deletion of stg increased uptake of serovar Typhi by human macrophages, and overexpression of stg in serovar Typhi and serovar Typhimurium strains reduced phagocytosis by human macrophages. These strains survived inside macrophages as well as the wild-type parent. Although the stgC gene contains a premature stop codon that disrupts the expected open reading frame encoding the usher and is therefore considered a pseudogene, our results show that the stg operon may encode a functional fimbria. Thus, this serovar Typhi-specific fimbrial operon contributes to interactions with host cells, and further characterization is important for understanding the role of the stg fimbrial cluster in typhoid fever pathogenesis.

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Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

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Contribution of thestgFimbrial Operon ofSalmonella entericaSerovar Typhi during Interaction with Human Cells

et al. 2007

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“…Therefore, it is of interest to investigate the signals or conditions that activate this genetic system. For S. Typhi, the selective capture of genes expressed in macrophages showed that the third component of the CRISPR/Cas system, STY3068 (casC ortholog), is induced under these conditions (17), and according to Deiwick et al (15), a minimal medium deficient in magnesium and phosphate simulates the environmental niche encountered by Salmonella in the eukaryotic cell, since several genes of Salmonella pathogenicity island 2 that are relevant to the survival of this pathogen inside macrophages are induced in this medium (10).…”

Section: Vol 193 2011mentioning

confidence: 99%

The CRISPR/Cas Immune System Is an Operon Regulated by LeuO, H-NS, and Leucine-Responsive Regulatory Protein in Salmonella enterica Serovar Typhi

et al. 2011

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Prokaryotes have developed multiple strategies to survive phage attack and invasive DNA. Recently, a novel genetic program denominated the CRISPR/Cas system was demonstrated to have a role in these biological processes providing genetic immunity. This defense mechanism is widespread in the Archaea and Bacteria, suggesting an ancient origin. In the last few years, progress has been made regarding the functionality of the CRISPR/Cas system; however, many basic aspects of the system remain unknown. For instance, there are few studies about the conditions and regulators involved in its transcriptional control. In this work, we analyzed the transcriptional organization of the CRISPR/Cas system as well as the positive and negative regulators involved in its genetic expression in Salmonella enterica serovar Typhi. The results obtained show that in S. Typhi the CRISPR/Cas system is a LeuO-dependent operon silenced by the global regulator LRP, in addition to the previously known nucleoidassociated protein H-NS; both LRP and H-NS bind upstream and downstream of the transcriptional start site of casA. In this study, relevant nucleotides of the casA regulatory region that mediate its LeuO transcriptional activation were identified. Interestingly, specific growth conditions (N-minimal medium) were found for the LeuOindependent expression of the CRISPR/Cas system in S. Typhi. Thus, our work provides evidence that there are multiple modulators involved in the genetic expression of this immune system in S. Typhi IMSS-1.

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“…To overcome these problems, the selective capture of transcribed sequences (SCOTS) was developed to identify bacterial genes expressed during infection (20). This technique has been successfully used with many pathogens, such as Mycobacterium, Salmonella, Actinobacillus, Helicobacter, and Streptococcus (4,8,12,15,21,27). SCOTS was recently used in combination with a DNA microarray in order to provide an effective way to elucidate the global bacterial expression profile, or transcriptome, from infected host cells (13).…”

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Escherichia coliO157:H7 Survives within Human Macrophages: Global Gene Expression Profile and Involvement of the Shiga Toxins

et al. 2008

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Escherichia coli O157:H7 is an important food-borne pathogen that specifically binds to the follicle-associated epithelium in the intestine, which rapidly brings this bacterial pathogen in contact with underlying human macrophages. Very little information is available about the interaction between E. coli O157:H7 and human macrophages. We evaluated the uptake and survival of strain EDL933 during infection of human macrophages. Surprisingly, EDL933 survived and multiplied in human macrophages at 24 h postinfection. The global gene expression profile of this pathogen during macrophage infection was determined. Inside human macrophages, upregulation of E. coli O157:H7 genes carried on O islands (such as pagC, the genes for both of the Shiga toxins, and the two iron transport system operons fit and chu) was observed. Genes involved in acid resistance and in the SOS response were upregulated. However, genes of the locus of enterocyte effacement or genes involved in peroxide resistance were not differentially expressed. Many genes with putative or unknown functions were upregulated inside human macrophages and may be newly discovered virulence factors. As the Shiga toxin genes were upregulated in macrophages, survival and cytotoxicity assays were performed with isogenic Shiga toxin mutants. The initial uptake of Shiga toxins mutants was higher than that of the wild type; however, the survival rates were significantly lower at 24 h postinfection. Thus, Shiga toxins are implicated in the interaction between E. coli O157:H7 and human macrophages. Understanding the molecular mechanisms used by E. coli to survive within macrophages may help in the identification of targets for new therapeutic agents.Enterohemorragic Escherichia coli (EHEC) causes an acute gastroenteritis, bloody diarrhea, and hemorrhagic colitis. Severe complications develop in up to 10% of cases, including the hemolytic-uremic syndrome, which can be fatal (45,56). EHEC strains share their genetic backbone with the laboratory strain K-12 and also contain 1.34 Mb of extra genetic material called O islands (OI) (46). In the EHEC strain EDL933 (O157: H7), 177 OI were identified; some of them harbor genes for important known virulence factors of EHEC, such as the locus of enterocyte effacement (LEE) and two different Shiga toxins, Stx1 and Stx2. Following the ingestion of contaminated food or water, EHEC enters the gastrointestinal tract, survives the acidic conditions of the stomach, and is released in the intestine. Adhesion of the bacteria to the intestinal wall is the first step in establishing infection. The LEE encodes a type III secretion system (T3SS) that injects effectors in host epithelial cells, creating an intimate binding, involving actin rearrangement and microvillus effacement, which results in the pathological lesions called attaching and effacing lesions (40, 52). In the large intestine, EHEC specifically adheres to the follicleassociated epithelium of Peyer's patches (47). Binding at the follicle-associated epithelium results in the rapid co...

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Selective Capture ofSalmonella entericaSerovar Typhi Genes Expressed in Macrophages That Are Absent from theSalmonella entericaSerovar Typhimurium Genome

Cited by 36 publications

References 33 publications

Contribution of thestgFimbrial Operon ofSalmonella entericaSerovar Typhi during Interaction with Human Cells

Contribution of thestgFimbrial Operon ofSalmonella entericaSerovar Typhi during Interaction with Human Cells

The CRISPR/Cas Immune System Is an Operon Regulated by LeuO, H-NS, and Leucine-Responsive Regulatory Protein in Salmonella enterica Serovar Typhi

Escherichia coliO157:H7 Survives within Human Macrophages: Global Gene Expression Profile and Involvement of the Shiga Toxins

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