What is it about?
Salmonella, which causes diarrhoea and other diseases, behaves differently depending on the environment it's in. When it's in parts of the human body, it acts in ways that allow it to cause disease. We know two genes that are responsible for directing this behaviour, and we removed them from Salmonella to get a better understanding of the things Salmonella does when it causes disease. What we learned from this were that the ability of Salmonella to swim, and to resist oxidative products from the human immune system (chemically similar to household bleach) are coordinated with the signature aspects of how Salmonella causes disease.
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Why is it important?
Most normal biological functions are inherited from a long familial line and are refined during that time. The distinctive disease causing traits of Salmonella evolved differently. They originated in a different organism- at some point in recent evolutionary time these traits jumped into Salmonella, and have subsequently been an important part of Salmonella biology. Since that jump, these traits have been subject to typical evolutionary processes in Salmonella just like other, garden variety functions. The findings in this paper are important because they demonstrate how the traits that jumped into Salmonella recently, through evolutionary processes, have come to have some control over the other, normal processes. It's another example of the complexity of evolution in it's mechanisms, and provides insight into understanding how Salmonella causes disease.
Perspectives
This work is the culmination of years of thinking and discussions with colleagues about the idea of how the disease causing traits of Salmonella, which jumped into Salmonella from a different organism, have affected the functions that Salmonella had before that jump. I didn't start this project aiming to address this issue, it presented itself when analyzing the data from that large scale experiments in the first stages of the project. So personally, it was very satisfying to see a hypothesis that was popular among me and my colleagues present itself so serendipitously. The findings are likely to be the tip of the iceberg in terms of how the original Salmonella functions have adapted to the traits that jumped in, and will serve as an example more broadly in biology where traits are acquired outside the normal, parent-child manner.
Nat Brown
Read the Original
This page is a summary of: A Horizontally Acquired Transcription Factor Coordinates Salmonella Adaptations to Host Microenvironments, mBio, September 2014, ASM Journals,
DOI: 10.1128/mbio.01727-14.
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