A genetic element present on megaplasmids allows Enterococcus faecium to use raffinose as carbon source.
Xinglin Zhang1, Joyce E P Vrijenhoek, Marc J M Bonten
1Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Environmental Microbiology
|October 16, 2010
Summary
Enterococcus faecium can metabolize raffinose sugar due to a specific gene cluster on megaplasmids. This ability, linked to alpha-galactosidases, aids adaptation and spread in various environments.
Area of Science:
- Microbiology
- Genetics
- Metabolic Engineering
Background:
- Enterococcus faecium is a common gut bacterium and an opportunistic nosocomial pathogen.
- Understanding Enterococcus faecium carbon metabolism is crucial for its adaptation to diverse ecological niches.
- The ability to utilize various sugars influences Enterococcus faecium's adaptability.
Purpose of the Study:
- To identify the genetic basis for raffinose metabolism in Enterococcus faecium.
- To investigate the prevalence and transferability of raffinose utilization genes.
- To understand the role of megaplasmids in Enterococcus faecium's metabolic capabilities.
Main Methods:
- Phenotypic testing of Enterococcus faecium isolates for raffinose growth.
- Genome analysis to identify relevant gene clusters (agaA and agaB).
- Gene disruption experiments and filter-mating to assess gene function and transfer.
Main Results:
- One Enterococcus faecium isolate (E980) demonstrated growth on raffinose.
- A unique gene cluster encoding two alpha-galactosidases (agaA and agaB) was identified in E980.
- Disruption of agaB, but not agaA, abolished raffinose utilization; genes are located on megaplasmids transferable via filter-mating.
Conclusions:
- Raffinose metabolism in Enterococcus faecium is mediated by the agaB gene, part of a megaplasmid-borne cluster.
- Megaplasmids carrying metabolic genes like those for raffinose utilization can significantly impact Enterococcus faecium's fitness and adaptability.
- Horizontal gene transfer of megaplasmids expands the metabolic potential of Enterococcus faecium, influencing its ecological success.
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