An international study led by a team of Canadian researchers has identified and reconstructed what is believed to be the first ancient E. coli genome using fragments of a 16th-century Italian mummy.
Researchers from McMaster University, in collaboration with the Université de Paris Cité, were able to reconstruct the ancient bacterium using gallstone extractions from the remains of a Neapolitan noble from the Renaissance period.
The researchers say the genome of E. coli’s “400-year ancestor” offers scientists a comparison to study how the bacterium evolved and adapted over time.
The discovery was published Thursday in the peer-reviewed journal Communications Biology and was funded by the Canadian Institute for Advanced Research.
Escherichia coli (E. coli) is a commensal bacterium that lives in the intestines of healthy people and animals. Although most strains of E. coli are harmless, others can cause serious illness, including outbreaks of sometimes fatal food poisoning and bloodstream infections.
The bacterium is known as an “opportunistic pathogen,” causing infections when a person experiences stress, an underlying disease, or an immunodeficiency. It is also known to be resistant to antibiotics and treatments.
THE. coli is a major public health problem, but it is not a source of pandemics. However, the researchers note that its evolution remained a mystery.
There is no historical record of deaths caused by E. coli, however, evolutionary geneticist McMaster Hendrik Poinar says its impact on health and mortality was likely to be significant.
“A rigorous focus on the pathogens driving the pandemic as the only narrative of mass mortality in our past ignores the heavy burden that comes from life-stress-driven opportunistic diners,” Poinar said in a press release.
According to the study, the mummified remains are those of Giovani d’Avalos, a 48-year-old noble who died in 1586. According to the researchers, he suffered from chronic inflammation of the gallbladder due to gallstones. His remains were recovered with a group of Italian nobles from the Abbey of San Domenico Maggiore in Naples in 1983.
“When we were examining these remains, there was no evidence that this man had the E. coli. Unlike an infection such as smallpox, there are no physiological indicators. Nobody knew what it was, “said George, lead author of the study and McMaster graduate student.
According to the researchers, isolating E. coli fragments from leftovers is complex because the bacterium lives in human microbiomes, but it can also be found in soil. The study author says the mummy’s gallbladder fragments were broken down by environmental contamination and had to work carefully to recover the DNA material and then rebuild the genome.
Researchers say E. coli was found to be a single strain, but still belonged to a phylogenetic lineage characteristic of human diners that still currently cause gallstones.
The study authors say ancient E. coli helps “paint a more complete picture of the opportunistic infection load of the past.”
“We were able to identify what an opportunistic pathogen was, delve into the functions of the genome, and provide guidelines to help researchers who might explore other hidden pathogens,” Long said in the release.