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1.
Appl Environ Microbiol ; 86(21)2020 10 15.
Article in English | MEDLINE | ID: mdl-32859594

ABSTRACT

Iron is a highly reactive metal that participates in several processes in prokaryotic and eukaryotic cells. Hosts and pathogens compete for iron in the context of infection. Chromobacterium violaceum, an environmental Gram-negative bacterial pathogen, relies on siderophores to overcome iron limitation in the host. In this work, we studied the role of the ferric uptake regulator Fur in the physiology and virulence of C. violaceum A Δfur mutant strain showed decreased growth and fitness under regular in vitro growth conditions and presented high sensitivity to iron and oxidative stresses. Furthermore, the absence of fur caused derepression of siderophore production and reduction in swimming motility and biofilm formation. Consistent with these results, the C. violaceum Δfur mutant was highly attenuated for virulence and liver colonization in mice. In contrast, a manganese-selected spontaneous fur mutant showed only siderophore overproduction and sensitivity to oxidative stress, indicating that Fur remained partially functional in this strain. We found that mutations in genes related to siderophore biosynthesis and a putative CRISPR-Cas locus rescued the Δfur mutant growth defects, indicating that multiple Fur-regulated processes contribute to maintaining bacterial cell fitness. Overall, our data indicated that Fur is conditionally essential in C. violaceum mainly by protecting cells from iron overload and oxidative damage. The requirement of Fur for virulence highlights the importance of iron in the pathogenesis of C. violaceumIMPORTANCE Maintenance of iron homeostasis, i.e., avoiding both deficiency and toxicity of this metal, is vital to bacteria and their hosts. Iron sequestration by host proteins is a crucial strategy to combat bacterial infections. In bacteria, the ferric uptake regulator Fur coordinates the expression of several iron-related genes. Sometimes, Fur can also regulate several other processes. In this work, we performed an in-depth phenotypic characterization of fur mutants in the human opportunistic pathogen Chromobacterium violaceum We determined that fur is a conditionally essential gene necessary for proper growth under regular conditions and is fully required for survival under iron and oxidative stresses. Fur also controlled several virulence-associated traits, such as swimming motility, biofilm formation, and siderophore production. Consistent with these results, a C. violaceumfur null mutant showed attenuation of virulence. Therefore, our data established Fur as a major player required for C. violaceum to manage iron, including during infection in the host.


Subject(s)
Bacterial Proteins/genetics , Chromobacterium/physiology , Chromobacterium/pathogenicity , Iron/toxicity , Oxidative Stress , Repressor Proteins/genetics , Siderophores/metabolism , Bacterial Proteins/metabolism , Repressor Proteins/metabolism , Virulence
2.
Infect Immun ; 87(12)2019 12.
Article in English | MEDLINE | ID: mdl-31570563

ABSTRACT

Bacteria use siderophores to scavenge iron from environmental or host sources. The iron acquisition systems of Chromobacterium violaceum, a ubiquitous environmental bacterium that can cause infections in humans, are still unknown. In this work, we demonstrated that C. violaceum produces putative distinct endogenous siderophores, here named chromobactin and viobactin, and showed that they are each required for iron uptake and virulence. An in silico analysis in the genome of C. violaceum revealed that genes related to synthesis and uptake of chromobactin (cba) and viobactin (vba) are located within two secondary-metabolite biosynthetic gene clusters. Using a combination of gene deletions and siderophore detection assays, we revealed that chromobactin and viobactin are catecholate siderophores synthesized from the common precursor 2,3-dihydroxybenzoate (2,3-DHB) on two nonribosomal peptide synthetase (NRPS) enzymes (CbaF and VbaF) and taken up by two TonB-dependent receptors (CbuA and VbuA). Infection assays in mice revealed that both the synthesis and the uptake of chromobactin or viobactin are required for the virulence of C. violaceum, since only the mutant strains that do not produce any siderophores or are unable to take up both of them were attenuated for virulence. In addition, the mutant strain unable to take up both siderophores showed a pronounced attenuation of virulence in vivo and reduced neutrophil extracellular trap (NET) formation in in vitro assays, suggesting that extracellularly accumulated siderophores modulate the host immune response. Overall, our results revealed that C. violaceum uses distinct endogenous siderophores for iron uptake and its establishment in the host.


Subject(s)
Chromobacterium/genetics , Chromobacterium/metabolism , Iron/metabolism , Siderophores/genetics , Siderophores/metabolism , Animals , Biological Transport/physiology , Chromobacterium/pathogenicity , Extracellular Traps/metabolism , Female , Hydroxybenzoates/metabolism , Mice , Mice, Inbred BALB C , Multigene Family/genetics , Neutrophils/metabolism , Peptide Synthases/metabolism
3.
Rev Inst Med Trop Sao Paulo ; 61: e7, 2019 Feb 14.
Article in English | MEDLINE | ID: mdl-30785561

ABSTRACT

Trypanosoma cruzi and Helicobacter pylori (HP) are pathogens that cause chronic diseases and have been associated with hypergastrinemia. The aim of this study was to evaluate the fasting gastrin levels in patients with different clinical forms of Chagas disease (CD), coinfected or not by HP. The enrolled individuals were outpatients attending at the university hospital. HP infection was assessed by serology and 13 C-urea breath test. Fasting serum gastrin concentration was measured by chemiluminescence assay. Gastric endoscopic and histological features were also evaluated. Associations between CD and serum gastrin level were evaluated in a logistical model, adjusting for age, gender and HP status. A total of 113 patients were evaluated (45 with Chagas disease and 68 controls). In the multivariate analysis, increasing serum gastrin levels (OR= 1.02; 95% CI= 1.01-1.12), increasing age (OR= 1.05; 95% CI= 1.02 - 1.09) and HP-positive status (OR = 2.88; 95% CI = 1.10 - 7.51) remained independently associated with CD. The serum gastrin levels were significantly higher in the group of patients with the cardiodigestive form ( P = 0.03) as well as with digestive form ( P = <0.001) of Chagas disease than in the controls. In conclusion, patients with cardiodigestive and digestive clinical forms of CD have increased basal serum gastrin levels in comparison with controls. Moreover, we also demonstrated that H. pylori coinfection contributes to the hypergastrinemia shown in CD.


Subject(s)
Chagas Disease/blood , Gastrins/blood , Helicobacter Infections/blood , Helicobacter pylori , Case-Control Studies , Chagas Disease/classification , Chagas Disease/complications , Coinfection , Cross-Sectional Studies , Female , Helicobacter Infections/complications , Humans , Male , Middle Aged
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