For millennia, humans have built narratives that put us at the centre of the Universe, typically placing our species as the Alpha and Omega of the world that surrounds us. During my teenage years, readings of Greek classics, or films by visionaries like Hayao Miyazaki, instilled in me a sense of unease towards those anthropocentric views. Over the years, I became more and more curious about identifying the underlying causes behind the events occurring around me, rather than following narratives that conveniently fit my worldview. This shift in perspective had professional implications and prompted the development of my research programme: to understand the evolutionary origins of human pathogens. As I was starting my PhD, I read one paper that left me in awe. The article came from the laboratory of Dr Ronald K. Taylor, who a few years later became my postdoctoral mentor. The work by Kirn et al. was published in Nature in 2005 and left an indelible mark that shaped the direction of my future research programme and the perspective from which I frame my scientific inquiries. In the article, the authors connect the ecological origins of one facultative pathogen, Vibrio cholerae, with its ability to colonize the human host.
V. cholerae is a natural dweller of aquatic biomes and only a phylogenomically confined group within the species, the pandemic cholera group, can cause the severe diarrhoeal disease cholera in humans. Cholera remains a major scourge in places with limited access to clean drinking water, with millions of yearly cases worldwide. Naturally, even though only members of the pandemic cholera group can cause the disease, their evolutionary roots originated in the aquatic environment, a habitat that they share with hundreds of other V. cholerae strains. To comprehend the evolutionary origins of V. cholerae virulence traits, Kirn et al. wondered whether there are common mechanisms that allow the bacterium to colonize the human host and its natural reservoirs. They discovered one colonization factor termed N-acetylglucosamine-binding protein A (GbpA) that mediates attachment to intestinal epithelial cells and is also important for the attachment of V. cholerae to one of its critical environmental reservoirs: the chitinaceous surface of crustaceans. GbpA binds to the aminosugar N-acetylglucosamine, a molecule that is both highly abundant in the mucus layer of the human intestine and the monomer that makes up chitin.
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