How Bacteria Evolved To Turn Into A Lethal Plague

Yersinia Pestis was the dreadful bacteria that caused major epidemics in our world’s history, epidemics like the Black Death. In a new research scientists have examined its genetic evolution and found that the acquisition of just one gene caused it to turn lethal from being harmless.

The study was conducted by a team of researchers from Northwestern University’s Feinberg School of Medicine, they examined the effects of ancestral strains of the bacteria in mouse models.

Studying the mouse models they determined that the ancestral bacteria could colonize the lung but was not the cause of the deadly infection that pneumonic plague is. This ability to infect the lung early on helped it find it new environments.

Wyndham Lathem, one of the study’s authors said they found how Yersinia Pestis had the ability to cause a severe respiratory infection very early in its evolution.

By being able to study its ancestry the researchers were better able to understand how the bacteria adapted to new environments by acquiring small bits of DNA.

Previously only causing gastrointestinal infections when Yersinia Pestis acquired the Pla gene it started causing the fatal pneumonic plague.

Pneumonic plague is a severe type of lung infection, the symptoms are fever, headache, weakness, and cough productive of bloody or watery saliva. The pneumonia progresses over 2 to 4 days and may cause septic shock and, without early treatment, death.

Person-to-person transmission of pneumonic plague occurs through respiratory droplets, which can only infect those who have face-to-face contact with the person who is ill.

The researchers modified the ancestral strains in animal models and noticed that it caused an illness similar to pneumonic plague, proving that the bacteria only needed the Pla gene to turn deadly.

The study published in Nature Communications also suggests that variations of the Pla gene helped the bacteria infect lymph nodes to cause bubonic plague.

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