Yersinia pestis DNA from skeletal remains from the 6(th) century AD reveals insights into Justinianic Plague

Abstract

Yersinia pestis, the etiologic agent of the disease plague, has been implicated in three historical pandemics. These include the third pandemic of the 19(th) and 20(th) centuries, during which plague was spread around the world, and the second pandemic of the 14(th)-17(th) centuries, which included the infamous epidemic known as the Black Death. Previous studies have confirmed that Y. pestis caused these two more recent pandemics. However, a highly spirited debate still continues as to whether Y. pestis caused the so-called Justinianic Plague of the 6(th)-8(th) centuries AD. By analyzing ancient DNA in two independent ancient DNA laboratories, we confirmed unambiguously the presence of Y. pestis DNA in human skeletal remains from an Early Medieval cemetery. In addition, we narrowed the phylogenetic position of the responsible strain down to major branch 0 on the Y. pestis phylogeny, specifically between nodes N03 and N05. Our findings confirm that Y. pestis was responsible for the Justinianic Plague, which should end the controversy regarding the etiology of this pandemic. The first genotype of a Y. pestis strain that caused the Late Antique plague provides important information about the history of the plague bacillus and suggests that the first pandemic also originated in Asia, similar to the other two plague pandemics.

Figure 1. Global phylogeny for Y. pestis.

This global phylogeny for Y. pestis is based upon figures 1A and S3B in Cui et al. . It includes four major branches (0–4) and is rooted with Y. pseudotuberculosis, the ancestor of Y. pestis . The identities of many of the major nodes defined by Cui et al. are presented in blue text. Circles represent specific populations; populations highlighted in gray have, to date, only been found in Asia , . Note that the location where strain Angola was isolated, which is the sole representative of population 0.PE3, is unknown. The phylogenetic position of Mongolian strain MNG 2972 is indicated with the blue box (see text). Five previously identified , key SNPs were utilized in the current study: s545, which occurs along the branch between nodes N06 and N07 (not shown); s87 and s89; which occur along the branch between N04 and N05; s82, which occurs along the branch between the branching point of strain MNG 2972 and N04; and s463, which occurs along the branch between the branching point of strain MNG 2972 and N03. It is known that these SNPs occur along these specific branches but the exact position and order of these SNPs along each branch is unknown. Sample A120 possesses ancestral states for SNPs s87, s89, and s545; and derived states for SNPs s82 and s463. Thus, the position of sample A120 in this phylogeny is along the branch between the branching point of strain MNG 2972 and N04, along branch N04-N05, along the branch from N04 to 0.ANT1 (red branches), or along one of the sub-branches within 0.ANT.1 (not shown). The phylogenetic positions of strains from the second pandemic , are indicated with the yellow boxes according to Cui et al. . The basal node for the 1.ORI group, which caused the third pandemic, is N14 .