scholarly journals Salmonella typhimurium Encodes a Putative Iron Transport System within the Centisome 63 Pathogenicity Island

1999 ◽  
Vol 67 (4) ◽  
pp. 1974-1981 ◽  
Author(s):  
Daoguo Zhou ◽  
Wolf-Dietrich Hardt ◽  
Jorge E. Galán
Keyword(s):  
Salmonella Typhimurium ◽  
Transport System ◽  
Minimal Medium ◽  
Iron Transport ◽  
Binding Protein ◽  
Pathogenicity Island ◽  
Nucleotide Composition ◽  
Growth Defect ◽  
Dependent Manner ◽  
Restricted Environment

ABSTRACT Upon entry into the host, Salmonella enterica strains are presumed to encounter an iron-restricted environment. Consequently, these bacteria have evolved a variety of often-redundant high-affinity acquisition systems to obtain iron in this restricted environment. We have identified an iron transport system that is encoded within the centisome 63 pathogenicity island of Salmonella typhimurium. The nucleotide composition of this locus is significantly different from that of the rest of this pathogenicity island, suggesting a different ancestry and a mosaic structure for this region of the S. typhimurium chromosome. This locus, designated sit, consists of four open reading frames which encode polypeptides with extensive homology to the yfe ABC iron transport system of Yersinia pestis, as well as other ABC transporters. The sitA gene encodes a putative periplasmic binding protein, sitB encodes an ATP-binding protein, and sitC and sitD encode two putative permeases (integral membrane proteins). This operon is capable of complementing the growth defect of the enterobactin-deficient Escherichia coli strain SAB11 in iron-restricted minimal medium. Transcription of the sitoperon is repressed under iron-rich growth conditions in afur-dependent manner. Introduction of a sitBCDdeletion into wild-type S. typhimuriumresulted in no apparent growth defect in either nutrient-rich or minimal medium and no measurable virulence phenotype. These results further support the existence of redundant iron uptake systems in S. enterica.

scholarly journals Regulation of expression of human intestinal bile acid-binding protein in Caco-2 cells

1998 ◽  
Vol 330 (1) ◽  
pp. 261-265 ◽  
Author(s):  
Tatsuo KANDA ◽  
Laurent FOUCAND ◽  
Yuichi NAKAMURA ◽  
Isabelle NIOT ◽  
Philippe BESNARD ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bile Acid ◽  
Western Blot ◽  
Bile Acids ◽  
Transport System ◽  
Binding Protein ◽  
Dependent Manner ◽  
Acid Binding Protein ◽  
Bile Acid Binding ◽  
Active Transport System

Molecular mechanisms of the bile acid active transport system in the ileal enterocytes remain unknown. We examined whether bile acids affect human enterocyte gene expression of intestinal bile acid-binding protein (I-BABP), a component of this transport system. Differentiated Caco-2 cells were incubated in the presence of human bile, bile acids or other lipids. The level of I-BABP expression was evaluated by Northern and Western blot analyses. A 24 h incubation of Caco-2 cells in a medium containing either bile or bile acids resulted in a remarkable 7.5-fold increase in the I-BABP mRNA level over the control level. Neither cholesterol, palmitic acid, phosphatidylcholine nor cholestyramine treated bile showed any difference in I-BABP mRNA expression from the control. Bile acid treatment increased the level of I-BABP mRNA in Caco-2 cells in a time- and dose-dependent manner. Western blot analysis showed that this induction led to increase in cytosolic I-BABP. Chenodeoxycholic acid and deoxycholic acid showed greater induction effects than other hydrophilic bile acids, including their own glycine conjugates. Pretreatment by actinomycin D or cycloheximide completely inhibited the up-regulation of I-BABP expression by bile acid. Bile acids, especially lipophilic bile acids, increase the I-BABP expression in Caco-2-cells, suggesting that luminal bile acids play an important role in regulating the I-BABP gene expression.

scholarly journals Anaerobic Regulation of Shigella flexneri Virulence: ArcA Regulates fur and Iron Acquisition Genes

2007 ◽  
Vol 189 (19) ◽  
pp. 6957-6967 ◽  
Author(s):  
Megan L. Boulette ◽  
Shelley M. Payne
Keyword(s):  
Transcription Factors ◽  
Transport System ◽  
Iron Transport ◽  
Iron Acquisition ◽  
Shigella Flexneri ◽  
Plaque Assay ◽  
Plaque Formation ◽  
Transport Systems ◽  
Dependent Manner ◽  
Anaerobic Conditions

ABSTRACT Invasion and plaque formation in epithelial monolayers are routinely used to assess the virulence of Shigella flexneri, a causative agent of dysentery. A modified plaque assay was developed to identify factors contributing to the virulence of S. flexneri under the anaerobic conditions present in the colon. This assay demonstrated the importance of the ferrous iron transport system Feo, as well as the global transcription factors Fur, ArcA, and Fnr, for Shigella plaque formation in anoxic environments. Transcriptional analyses of S. flexneri iron transport genes indicated that anaerobic conditions activated feoABC while repressing genes encoding two other iron transport systems, the ABC transporter Sit and the Iuc/Iut aerobactin siderophore synthesis and transport system. The anaerobic transcription factors ArcA and Fnr activated expression of feoABC, while ArcA repressed iucABCD iutA. Transcription of fur, encoding the iron-responsive transcriptional repressor of bacterial iron acquisition, was also repressed anaerobically in an ArcA-dependent manner.

scholarly journals The aerobactin iron transport system genes in Shigella flexneri are present within a pathogenicity island

1999 ◽  
Vol 33 (1) ◽  
pp. 63-73 ◽  
Author(s):  
Steven A. Vokes ◽  
Stephanie A. Reeves ◽  
Alfredo G. Torres ◽  
Shelley M. Payne
Keyword(s):  
Transport System ◽  
Iron Transport ◽  
Shigella Flexneri ◽  
Pathogenicity Island

scholarly journals Differential Modulation of Burkholderia cenocepacia Virulence and Energy Metabolism by the Quorum-Sensing Signal BDSF and Its Synthase

2009 ◽  
Vol 191 (23) ◽  
pp. 7270-7278 ◽  
Author(s):  
Yinyue Deng ◽  
Calvin Boon ◽  
Leo Eberl ◽  
Lian-Hui Zhang
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Minimal Medium ◽  
Virulence Gene ◽  
Burkholderia Cenocepacia ◽  
Signal Interference ◽  
Growth Defect ◽  
Infection Model ◽  
Dependent Manner ◽  
Virulence Gene Expression

ABSTRACT Burkholderia cenocepacia produces the molecule cis-2-dodecenoic acid (BDSF), which was previously shown to play a role in antagonism against the fungal pathogen Candida albicans by interfering with its morphological transition. In this study, we show that production of BDSF is under stringent transcriptional control and the molecule accumulates in a cell density-dependent manner, typically found with quorum-sensing (QS) signals. B. cenocepacia mutant strain J2315 with a deleted Bcam0581 gene, which encodes an enzyme essential for BDSF production, exhibited a growth defect in minimal medium but not in rich medium, decreased virulence gene expression, and attenuated virulence in a zebrafish infection model. Exogenous addition of BDSF to the mutant rescues virulence gene expression but fails to restore its growth defect in minimal medium. We show that Bcam0581, but not BDSF, is associated with B. cenocepacia ATP biogenesis. We also provide evidence that some of the BDSF-regulated genes are also controlled by the acyl-homoserine-lactone-dependent QS system and are thus coregulated by two cell-to-cell signaling systems. These data demonstrate that in addition to the role in cross-kingdom signal interference, BDSF and its synthase are also important for the virulence and physiology of B. cenocepacia.

Hemoglobin Enhances the Binding of Bacterial Endotoxin to Human Endothelial Cells

1996 ◽  
Vol 76 (02) ◽  
pp. 258-262 ◽  
Author(s):  
Robert I Roth
Keyword(s):  
Endothelial Cells ◽  
Binding Protein ◽  
Bacterial Endotoxin ◽  
Dependent Manner ◽  
Serum Free Medium ◽  
Free Medium ◽  
Human Endothelial Cells ◽  
Serum Factors ◽  
Serum Free ◽  
Lps Binding

SummaryHuman endothelial cells, when incubated with bacterial endotoxin (lipopolysaccharide, LPS), modify their surface in association with prominent production of procoagulant tissue factor (TF) activity. This deleterious biological effect of LPS has been shown previously to be enhanced approximately 10-fold by the presence of hemoglobin (Hb), a recently recognized LPS binding protein that causes disaggregation of LPS and increases the biological activity of LPS in a number of in vitro assays. The present study was performed to test the hypothesis that Hb enhances the LPS-induced procoagulant activity of human umbilical vein endothelial cells (HUVEC) by increasing LPS binding to the cells. The binding of 3H-LPS to HUVEC was determined in the absence or presence of Hb or two other known LPS-binding proteins, human serum albumin (HSA) and IgG. LPS binding was substantially increased in the presence of Hb, in a Hb concentration-dependent manner, but was not increased by HSA or IgG. Hb enhancement of LPS binding was observed in serum-free medium, indicating that there was no additional requirement for any of the serum factors known to participate in the interaction of LPS with cells (e.g., lipopolysaccharide (LPS)-binding protein (LBP) and soluble CD14 (sCD14)). Hb enhancement of LPS binding also was observed in the more physiologic condition of 100% plasma. LPS-induced TF activity was stimulated by Hb, but not by HSA or IgG. In serum-free medium, TF activity was not stimulated under any of the conditions tested. Ultrafiltration of LPS was dramatically increased after incubation with Hb but not with HSA or IgG, suggesting that LPS disaggregation by Hb was responsible for the enhanced binding of LPS to HUVEC and the subsequent stimulation of TF activity.

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