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Published on: December 23, 2022
An in silico analysis of osmotolerance in the emerging gastrointestinal pathogen Cronobacter sakazakii
1Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland.
Insights
Cronobacter sakazakii, a pathogen causing infant mortality, survives low water activity in powdered infant formula. This study identified 53 osmotolerance loci, revealing multiple gene copies that enhance survival.
Area of Science:
- Microbiology
- Genomics
- Food Safety
Background:
- Cronobacter sakazakii is an emerging gastrointestinal pathogen responsible for high infant mortality.
- Powdered infant formula (PIF), with low water activity (aw), is a primary transmission route for C. sakazakii.
- Understanding C. sakazakii's osmotolerance is critical for preventing infant infections.
Purpose of the Study:
- To investigate the genetic mechanisms behind C. sakazakii's ability to survive in low water activity environments.
- To identify specific osmotolerance loci in the C. sakazakii genome.
- To provide a comprehensive overview of C. sakazakii's osmoregulation.
Main Methods:
- Comparative genomics approach.
- Review of bacterial osmoadaptation mechanisms.
- Homology transfer to identify osmotolerance loci in C. sakazakii.
- Analysis of gene copy number variations.
Main Results:
- Identified 53 osmotolerance loci in C. sakazakii, encompassing both hyper- and hypo-osmotic stress responses.
- C. sakazakii possesses multiple copies of key osmotolerance genes, including seven proP homologues and two OpuC systems.
- The pathogen shares osmotolerance loci with Escherichia coli but exhibits unique gene duplication patterns.
Conclusions:
- C. sakazakii's enhanced osmotolerance is attributed to multiple copies of specific osmotolerance loci.
- The osmotic stress response is regulated at multiple levels (transcriptional, translational, post-translational), with RpoS as a likely global regulator.
- Findings provide insights into C. sakazakii's persistence in PIF, informing food safety strategies.
Abstract:
Up to 80% of infants infected with Cronobacter sakazakii die within days of birth, making this emerging gastrointestinal pathogen a serious cause for concern. The mode of transmission most often associated with C. sakazakii infection is powdered infant formula (PIF), which typically has a water activity (aw) of ca 0.2--inhospitable to most bacterial pathogens. In the current study a comparative genomic approach was used to investigate the distinctive ability of this pathogen to survive and persist in such low aW conditions. A comprehensive review of the mechanisms involved in bacterial osmoadaptation was followed by an exhaustive homology transfer based approach to identify putative osmotolerance loci in the C. sakazakii genome. In total 53 osmotoleance loci were identified, including both hyper- and hypo-osmotic stress response systems, helping to construct a concise overview of the C. sakazakii osmotolerance response. Interestingly, while C. sakazakii contains homologues of all the principal osmotolerance loci of Escherichia coli; a key difference is that C. sakazakii contains multiple copies of certain osmotolerance loci; including seven copies of the E. coli proP homologue and two copies of OpuC--a multi component carnitine uptake system associated with Listeria monocytogenes and which has also been found to transport other compatible solutes such as glycine betaine, proline, ectoine and choline. Furthermore, the osmotic stress response of C. sakazakii appears to be regulated at the transcriptional, translational and post-translational levels, with RpoS most likely functioning as the global transcriptional regulator of the osmotolerance response.
