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Identification and characterization of Cronobacter iron acquisition systems.

ABSTRACT: Cronobacter spp. are emerging pathogens that cause severe infantile meningitis, septicemia, or necrotizing enterocolitis. Contaminated powdered infant formula has been implicated as the source of Cronobacter spp. in most cases, but questions still remain regarding the natural habitat and virulence potential for each strain. The iron acquisition systems in 231 Cronobacter strains isolated from different sources were identified and characterized. All Cronobacter spp. have both the Feo and Efe systems for acquisition of ferrous iron, and all plasmid-harboring strains (98%) have the aerobactin-like siderophore, cronobactin, for transport of ferric iron. All Cronobacter spp. have the genes encoding an enterobactin-like siderophore, although it was not functional under the conditions tested. Furthermore, all Cronobacter spp. have genes encoding five receptors for heterologous siderophores. A ferric dicitrate transport system (fec system) is encoded specifically by a subset of Cronobacter sakazakii and C. malonaticus strains, of which a high percentage were isolated from clinical samples. Phylogenetic analysis confirmed that the fec system is most closely related to orthologous genes present in human-pathogenic bacterial strains. Moreover, all strains of C. dublinensis and C. muytjensii encode two receptors, FcuA and Fct, for heterologous siderophores produced by plant pathogens. Identification of putative Fur boxes and expression of the genes under iron-depleted conditions revealed which genes and operons are components of the Fur regulon. Taken together, these results support the proposition that C. sakazakii and C. malonaticus may be more associated with the human host and C. dublinensis and C. muytjensii with plants.

SUBMITTER: Grim CJ

PROVIDER: S-EPMC3416605 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Identification and characterization of Cronobacter iron acquisition systems.

Grim C J CJ Kothary M H MH Gopinath G G Jarvis K G KG Beaubrun J Jean-Gilles JJ McClelland M M Tall B D BD Franco A A AA

Applied and environmental microbiology 20120615 17

Cronobacter spp. are emerging pathogens that cause severe infantile meningitis, septicemia, or necrotizing enterocolitis. Contaminated powdered infant formula has been implicated as the source of Cronobacter spp. in most cases, but questions still remain regarding the natural habitat and virulence potential for each strain. The iron acquisition systems in 231 Cronobacter strains isolated from different sources were identified and characterized. All Cronobacter spp. have both the Feo and Efe syst ...[more]

PMID: 22706064

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Project description:UnlabelledClostridium difficile is an anaerobic, Gram-positive, spore-forming opportunistic pathogen and is the most common cause of hospital-acquired infectious diarrhea. Although iron acquisition in the host is a key to survival of bacterial pathogens, high levels of intracellular iron can increase oxidative damage. Therefore, expression of iron acquisition mechanisms is tightly controlled by transcriptional regulators. We identified a C. difficile homologue of the master bacterial iron regulator Fur. Using targetron mutagenesis, we generated a fur insertion mutant of C. difficile. To identify the genes regulated by Fur in C. difficile, we used microarray analysis to compare transcriptional differences between the fur mutant and the wild type when grown in high-iron medium. The fur mutant had increased expression of greater than 70 transcriptional units. Using quantitative reverse transcriptase PCR (qRT-PCR), we analyzed several of the Fur-regulated genes identified by the microarray and verified that they are both iron and Fur regulated in C. difficile. Among those Fur- and iron-repressed genes were C. difficile genes encoding 7 putative cation transport systems of different classes. We found that Fur was able to bind the DNA upstream of three Fur-repressed genes in electrophoretic mobility shift assays. We also demonstrate that expression of Fur-regulated putative iron acquisition systems was increased during C. difficile infection using the hamster model. Our data suggest that C. difficile expresses multiple iron transport mechanisms in response iron depletion in vitro and in vivo.ImportanceClostridium difficile is the most common cause of hospital-acquired infectious diarrhea and has been recently classified as an "urgent" antibiotic resistance threat by the CDC. To survive and cause disease, most bacterial pathogens must acquire the essential enzymatic cofactor iron. While import of adequate iron is essential for most bacterial growth, excess intracellular iron can lead to extensive oxidative damage. Thus, bacteria must regulate iron import to maintain iron homeostasis. We demonstrate here that C. difficile regulates expression of several putative iron acquisition systems using the transcriptional regulator Fur. These import mechanisms are induced under iron-limiting conditions in vitro and during C. difficile infection of the host. This suggests that during a C. difficile infection, iron availability is limited in vivo.

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Identification and characterization of Cronobacter iron acquisition systems.

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Identification and characterization of Cronobacter iron acquisition systems.

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