A 16th-century mummy helped scientists reconstruct the DNA of an E. coli

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An international collaboration of researchers has succeeded in reconstructing the genome of an E. coli from the remains of an Italian nobleman, mummified in the 16th century, a press release says.

Escherichia coli (E. coli) was originally thought to be a commensal – a microscopic organism that resides in the host’s body offering no benefit but causing no harm either. Over the years, scientists have discovered that inside the human intestine, E. coli helps us digest our food, protecting us from other infections, while helping to vitamin K production and B12.

But E.coli also has a nasty side. When the host body is under stress or has low immunity, E. coli assumes the role of an opportunistic pathogen that can launch a full-fledged attack on the host if it manages to enter the bloodstream, tracts urine or kidneys. Certain strains of the organism can also cause food poisoning and serious, even fatal, infections.

A silent killer in us?

Although. coli has often been associated with sporadic epidemics, it has never been considered as an organism with pandemic capacity, even if it is very resistant to treatment. Hendrik Poinar, an evolutionary geneticist at McMaster University in Canada, who participated in the research, said: “a strict focus on the pathogens causing the pandemic as the only narrative of mass mortality in our past misses the heavy burden that comes from opportunistic messmates. [such as E.coli].”

The researchers say that although we don’t have historical records of deaths caused by organisms like E. coli, their impact on human health and mortality has likely been enormous. To understand the evolutionary history of the organism, such as where it acquired its new genes or its resistance to antibiotics, researchers needed the genome of its ancestor, and the mummified remains from the 16th century were a good opportunity to achieve it.

The mummified Italian nobleman

Well-preserved mummified remains used in this study were found in 1983 at the Abbey of Saint Domenico Maggiore in the city of Naples, Italy. One of the remains has been confirmed to be that of Giovani d’Avalos, a Neapolitan nobleman from the Renaissance period. In 1586, d’Avalos died at the age of 48 from what is believed to be chronic inflammation of the gallbladder due to gallstones, the press release said.

Unlike infections like smallpox, the noble had no visible signs of infection, so there was no evidence that he also had an E. coli infection. The team worked meticulously to isolate the sample fragments while protecting them from environmental contamination. The recovered material was used to reconstruct the E. coli genome.

“It was so emotional to be able to hit this former E.coli and discover that, although unique, it belonged to a phylogenetic lineage characteristic of human commensals that still cause gallstones today,” said Erick Denamur, professor of biochemistry and molecular biology at Paris Cité University, who also participated in the study.

The results of the study were published today in the journal Communications Biology.

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