Essay On Yersinia Pestis

There have been few times in the history of the human race where civilization has been under the threat of extinction. One such time, arguably the most infamous, was when the Black Death ravaged the western hemisphere. For several hundred years, the cause of this devastating disease remained a mystery, however, recent analysis from the DNA of the victims of the plague indicate that Yersinia pestis a bacillus shaped bacterium, was the likely cause of this tragedy (Perry and Fetherston, 1997). The road leading up to Y. pestis becoming God’s bacterial agent of judgement was a relatively short one, as evidence suggests that the bacteria had divulged from Yersinia pseudotuburculosis as close to 800 years beforehand (Chain et al., 2004).
This change in the genome of Y. pseudotuburculosis actually yielded eight separate populations of the species Y. pestis, distinct only in the slight variations of their DNA (Achtman et al., 2004). These distinct populations are known as biovars. Three of these biovars, known as Antiqua, Medievalis, and Orientalis, have started endemic plagues: the Justinian plague in the sixth century, the Black Death in …show more content…
This was because the hemin storage locus (hms locus) was modified in this particular population of Y. pestis so that it infected the midgut instead of the proventriculus, a spiny chamber between the midgut and the esophagus. This in turn, caused the fleas to overindulge themselves, as the blood they were feeding on pooled in the proventriculus, until the point of regurgitation of blood contaminated with the bacteria (Hinnebusch et al., 1996). This modification of the hms locus almost caused the extinction of many countries, as the more populated areas such as Italy and Paris suffered losses of up to 80% of their pre-plague levels due to the levels of transference caused by the fleas