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Identification and characterization of Cronobacter iron acquisition systems
C J Grim1, M H Kothary, G Gopinath
1CFSAN, FDA, Laurel, Maryland, USA.
Applied and Environmental Microbiology
|June 19, 2012
Summary
Cronobacter bacteria, a threat in infant formula, possess diverse iron acquisition systems. Specific systems suggest Cronobacter sakazakii and C. malonaticus are human-associated, while C. dublinensis and C. muytjensii may be plant-associated.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Genomics
Background:
- Cronobacter spp. are emerging pathogens linked to severe infant illnesses, often traced to contaminated powdered infant formula.
- Despite formula contamination being a known source, the natural habitat and virulence factors of Cronobacter strains require further investigation.
- Iron acquisition is crucial for bacterial survival and virulence, making these systems key targets for understanding Cronobacter ecology.
Purpose of the Study:
- To identify and characterize the iron acquisition systems in a diverse collection of Cronobacter strains.
- To investigate the potential correlation between specific iron acquisition systems and the ecological niche (human vs. plant) of different Cronobacter species.
- To elucidate the regulatory network (Fur regulon) governing iron metabolism in Cronobacter.
Main Methods:
- Genomic analysis of 231 Cronobacter strains to identify genes encoding iron uptake systems (Feo, Efe, siderophores, and their receptors).
- Phylogenetic analysis to compare the ferric dicitrate (fec) transport system with homologous genes in other bacteria.
- Gene expression studies under iron-depleted conditions and identification of Fur boxes to define the Fur regulon.
Main Results:
- All Cronobacter strains possess ferrous iron uptake systems (Feo, Efe) and most (98%) have cronobactin for ferric iron transport.
- A ferric dicitrate (fec) transport system, phylogenetically related to human-pathogenic strains, was found in a subset of Cronobacter sakazakii and C. malonaticus, often from clinical sources.
- Cronobacter dublinensis and C. muytjensii strains encode receptors for plant-pathogenic siderophores, suggesting a plant association.
Conclusions:
- Cronobacter sakazakii and C. malonaticus, possessing the fec system, may be more adapted to the human host.
- Cronobacter dublinensis and C. muytjensii, with receptors for plant siderophores, are likely associated with plant environments.
- Understanding these iron acquisition systems provides insights into the ecological niches and potential virulence of different Cronobacter species.
