Harbeck, M. | Search bioRxiv

bioRxiv2018

A phylogeography of the second plague pandemic revealed through the analysis of historical Y. pestis genomes

The second plague pandemic (14th - 18th century AD), caused by the bacterium Yersinia pestis, is infamous for its initial wave, the Black Death (1346-1353 AD), and its repeated scourges in Europe and the vicinity until the Early Modern Era. Here, we report 32 ancient Y. pestis genomes spanning the 14th to 17th century AD through the analysis of human remains from nine European archaeological sites. Our data support an initial entry of the bacterium from Eastern Europe and the absence of genetic diversity during the Black Death as well as low diversity during local outbreaks thereafter. Moreover, analysis of post-Black Death genomes shows the diversification of a Y. pestis lineage into multiple genetically distinct clades that may have given rise to more than one disease reservoir in, or close to, Europe. Finally, we show the loss of a genomic region that includes virulence-associated genes in strains associated with late stages of the second plague pandemic (17th - 18th century AD). This deletion could not be detected in extant strains within our modern dataset, though it was identified in a today-extinct lineage associated with the first plague pandemic (6th - 8th century AD), suggesting convergent evolution during both pandemic events.

evolutionary biology↗

bioRxiv2018

Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541-750)

The first historically documented pandemic caused by Yersinia pestis started as the Justinianic Plague in 541 within the Roman Empire and continued as the so-called First Pandemic until 750. Although palaeogenomic studies have previously identified the causative agent as Y. pestis, little is known about the bacteriums spread, diversity and genetic history over the course of the pandemic.\n\nTo elucidate the microevolution of the bacterium during this time period, we screened human remains from 20 sites in Austria, Britain, Germany, France and Spain for Y. pestis DNA and reconstructed six new genomes. We present a novel methodological approach assessing SNPs in ancient bacterial genomes, facilitating qualitative analyses of low coverage genomes from a metagenomic background. Phylogenetic analysis reveals the existence of previously undocumented Y. pestis diversity during the 6th-7th centuries, and provides evidence for the presence of multiple distinct Y. pestis strains in Europe. We offer genetic evidence for the presence of the Justinianic Plague in the British Isles, previously only hypothesized from ambiguous documentary accounts, as well as southern France and Spain, and that southern Germany seems to have been affected by at least two distinct Y. pestis strains. Four of the reported strains form a polytomy similar to others seen across the Y. pestis phylogeny, associated with the Second and Third Pandemics. We identified a deletion of a 45 kb genomic region in the most recent First Pandemic strain affecting two virulence factors, intriguingly overlapping with a deletion found in 17th-18th-century genomes of the Second Pandemic.\n\nSignificance StatementThe first historically reported pandemic attributed to Yersinia pestis started with the Justinianic Plague (541-544) and continued for around 200 years as the so-called First Pandemic. To date, only one Y. pestis strain from this pandemic has been reconstructed using ancient DNA. In this study, we present six new genomes from Britain, France, Germany and Spain, demonstrating the geographic range of plague during the First pandemic and showing microdiversity in the Early Medieval Period. Moreover, we detect similar genome decay during the First and Second Pandemic (17th to 18th century) that includes the same two virulence factors, thus providing an example of potential convergent evolution of Y. pestis during large scale epidemics.

evolutionary biology↗