Updated: March 6, 2021 3:31:55 pm
Researchers at the University of Hyderabad (UoH), while studying the genomes of bacterial strains of E. coli, have found that 12% of such variants of mainly extra-intestinal origin could pose threats of progression of colorectal cancer.
The findings of the study were published in the form of a paper titled ‘Evolutionary Dynamics Based on Comparative Genomics of Pathogenic Escherichia coli Lineages Harboring Polyketide Synthase (pks) Island’ in the March 2, 2021 issue of an international journal called ‘mBio’, which is published by the American Society for Microbiology.
Researchers from Robert Koch Institute in Berlin and Dr. D.Y. Patil Vidyapeeth in Pune also participated in the study.
“This risk is basically attributable to a special class of bacterial metabolites called polyketides. It appears that polyketide carrying strains are evolving and spreading,” the paper states.
E. coli is a common bacterium found in the lower intestine and also in the environment, contaminated food and water.
The research team led by Prof Niyaz Ahmed, Department of Biotechnology and Bioinformatics at the School of Life Sciences in UoH, examined over five years 4,000 genomes of bacterial strains of E. coli using high-throughput comparative genomics and phylogenetic analyses. The aim was to understand the prevalence and epidemiology of the bacteria that produce colibactin, a genotoxin that causes DNA breaks leading to cancer.
According to Prof Ahmed, pathogenic E. coli strains are evolving with the horizontal acquisition of mobile genetic elements, including pathogenicity islands that produce colibactin, resulting possibly in severe clinical outcomes.
Speaking to indianexpress.com, Professor Ahmed said that the high-end computational informatics study led to certain conclusions on the evolution of E. coli.
“During evolution, they acquire certain genes and lose certain others. So, the process continues on an evolutionary time-scale. And they are not the only bacteria — there are trillions of organisms in the gut. And they are likely to get a foothold and secrete toxins such as colibactin over a period of time and try to become dominant,” said Prof Ahmed.
He added, “We consider such strains to be risk factors and not causative agents because the triggers could be multiple but they are surely the main risk factors for progression.”
These ideas need to be further tested in real-life situations, beyond computer platforms.
The study found out that though these types of strains are relatively small in number in nature as compared to other non-toxigenic E. coli populations, there is a danger that due to horizontal gene transfers occurring frequently in bacteria, the genotoxin encoding islands could be acquired by or shared with other innocuous bacteria as well. The study also highlights that good hygiene and sanitation could keep them at bay.
The study adopts a fundamental data-science approach that may support diagnostic systems or healthcare modalities aimed at understanding clinical implications of the potential bacterial toxins (read genotoxins) that are associated with colorectal cancer progression, Professor Ahmed said, adding that such studies are the main requirements for an exact risk assessment at population levels and hence significant.
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