What is it about?
Digestion breaks complex nutrients like proteins into small fragments called amino acids. These are taken up by our bodies and used for energy. As a result, the amount of amino acid decreases as we descend towards the end of the gut. Enterohaemorrhagic E. coli (EHEC) causes nasty food poisoning disease both within the gut, and in serious cases can affect the kidneys and the brain. One of the main reasons for its destructive capabilities is that it attaches very tightly to the lining of the end of the human gut where amino acid is lowest. Here we show that when these bacteria break down amino acids, the breakdown products prevent production of factors required for attachment. In fact, these attachment factors are most strongly produced when the bacteria are starved of nitrogen, a component of amino acids. The bacteria in question were known to break down L-serine, but we show that this attachment control also happens with D-serine – an amino acid with a mirror image shape compared to L-serine. This leads us to propose that D-serine is also broken down to control attachment.
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Why is it important?
This is important because several amino acids could be used to treat infections with EHEC. It also sheds light on why EHEC bacteria do not cause infections outside of the gut – a capability held by other types of E. coli.
Perspectives
This research was a labour of love over several years. What started as a side quest to a postdoctoral research project grew into a cross-borders collaboration between the Roe and O’Boyle Groups. The study pushed us beyond our comfort zones, into engagements with metabolomics experts to finally reveal the mechanism by which EHEC adhesion is controlled by both mirror forms of serine. While there is much remaining to uncover about the effects of D-serine stress, it is incredibly satisfying to now be able to reveal the mechanism of virulence regulation at play. We hope readers enjoy our insight into the hard wiring of this destructive bacterial pathogen.
Dr Nicky O'Boyle
University of Dublin Trinity College
Read the Original
This page is a summary of: Catabolism of serine enantiomers represses enterohemorrhagic
Escherichia coli
virulence factors via modulation of the nitrogen stress response, Proceedings of the National Academy of Sciences, March 2026, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2532916123.
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