Y. Pestis

Interesting research being done on the microbe that caused the Black Death:

While studying Yersinia pestis, the bacteria responsible for epidemics of plague such as the Black Death, researchers have found a single small genetic change that fundamentally influenced the evolution of the deadly pathogen, and thus the course of human history.

In a paper published in Nature Communications, Wyndham Lathem, Ph.D., assistant professor in microbiology-immunology at Northwestern University Feinberg School of Medicine, and first author Daniel Zimbler, Ph.D., a Feinberg post-doctoral fellow, demonstrated how the acquisition of a single gene caused the shift of Y. pestis from causing a primarily gastrointestinal infection to a more serious and often fatal respiratory disease.

They further showed how later modifications of this gene enhanced infections associated with the bubonic plague.

Lathem and his team inserted the Pla gene into this strain to observe changes in the health of the lungs. They found the newly mutated strain had gained the ability to cause respiratory infection identically to modern strains of Y. pestis that cause disease today, demonstrating that the Pla gene was necessary for Y. pestis to infect the lungs. In addition, they found that no other changes to Y. pestis were required, even though the bacteria has continued to gain and lose genes over the last several thousand years.

The lab also looked at variations of the gene Pla and discovered that a single modification only found in modern strains of Y. pestis was a critical adaptation for the bacteria to spread in the body and infect the lymph nodes, a form of the infection that causes bubonic plague. According to Lathem, the surprising conclusion from this aspect of the study is that, contrary to current thinking in the field, Y. pestis may have first evolved as a respiratory pathogen before it could cause the more common form of disease, bubonic plague.

Lathem said the new research may explain how Y. pestis transitioned from causing only localized outbreaks of plague to the pandemic spread of Y. pestis such as the sixth century’s Justinian Plague and the fourteenth century’s Black Death.