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Scientists have decoded how the toxin produced by the deadly typhoid bacterium hijacks an infected cell's natural DNA repair mechanism, and accelerates its ageing -- an advance that may help develop strategies to combat the killer disease.
As part of the study, published in the journal Nature Communications, researchers infected human cells cultured in a lab with the bacterial pathogen that causes typhoid -- Salmonella typhi.
According to the study, the DNA in our cells is constantly under threat by environmental factors such as smoking and ultraviolet (UV) light, but cells usually have robust DNA repair machines to combat these threats.
Using fluorescent microscopes to study how the toxin damaged the DNA at the molecular level, they discovered that it induces a peculiar form of DNA damage.
"Our findings have shown that pathogenic bacteria can speed up cellular ageing through a toxin and take advantage of this to establish infections" said Daniel Humphreys, lead author of the study from the University of Sheffield in the UK.
Angela Ibler, who made the discovery, dubbed the DNA damage response RING -- Response induced by a Genotoxin -- in reference to the single-strand breaks in the double helix of DNA that accumulate in a signature ring-like pattern.
"Until now, how the typhoid toxin of Salmonella Typhi contributed to infection had been a mystery," Professor Sherif El-Khamisy, who co-led the study, said.
According to a 2018 World Health Organization (WHO) report, typhoid fever is a major killer in low and middle-income countries, affecting 21 million people annually, and causing 168,000 deaths.
The researchers now hope to further investigate how this discovery can be exploited to help us diagnose and treat typhoid, and also determine whether the RING phenotype is a signature of other diseases associated with DNA damage, such as cancer.
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