Ancient DNA unravels the mystery of black death

In a recent study published in Nature Journals, researchers, plague outbreaks Yersinia pestis Started in Central Eurasia during 14 years^th century.

Study: Causes of black death in central Eurasia in the 14th century. Image Credits: Everett Collection / Shutterstock

Background

Bacterial plague outbreak Yersinia pestis ((((Yersinia pestis) Was the first wave of a second plague outbreak, one of the major infectious disease disasters in human history, lasting about 500 years. During those eight years, the plague outbreak wiped out about 60% of the population of western Eurasia.

Due to the long-term and widespread demographic effects of the pandemic, the origin of the medieval plague pandemic from 1346 to 1353 AD is under continuous investigation. Unfortunately, despite extensive interdisciplinary research, the location of the second plague outbreak is unknown.

To date, the most controversial archaeological evidence that a plague outbreak has begun comes from the cemetery around Lake Issyk Kul in modern Kyrgyzstan. The tombstone inscription, dated exactly 1338-1339, mentions “plague” as the cause of death, so it is possible that 14 victims lived on these sites.^th-Century fads.

About research

In this study, researchers documented information on seven ancient deoxyribonucleic acid (aDNA) excavated from the Brana and Karazigach cemeteries near Lake Isikkul, which may be related to the cause of the second plague pandemic. Investigate some evidence. Excavations of these cemeteries around 1885 and 1892 revealed a unique archaeological community that may be associated with 14.^th-Century epidemics that have influenced the region.

Issyk Kul Lake on a summer day in Kyrgyzstan. Image credit: V. Smirnov / Shutterstock

To find out more about the situation at the Brana Cemetery and the Karajgach Cemetery, the team translated and investigated existing archived evidence from the excavations of these tombs. Next, they used hybridization captures of approximately 1.24 million ancestral single nucleotide polymorphisms (SNPs) to generate human genome data from 7 individuals (5 from Kara-Djigach and 2 from Burana). did. This process resulted in four individuals with sufficient genomic coverage for population genetic evaluation, or over 30,000 SNPs. In addition, scientists used ancestor modeling and component analysis to analyze genomic data generated from seven individuals.

Shotgun metagenome details from seven individuals utilize heuristic operations in the Pathogen Screening (HOPS) pipeline to assess signs of ancient pathogen DNA that can elucidate the presumed cause of the epidemic. It was classified taxonomically. The authors also analyzed the SNP patterns of BSK003 and BSK001. Yersinia pestis Genome to see if they represent different bacterial strains. They used MALT software to perform taxonomically informative metagenomic screening to reduce variant calls due to environmental pollution. This was important given the large number of multiallelic domains found in both genomes.

Researchers have compared the Kara-Djigach genome with previously documented historical and currently circulating ones. Yersinia pestis Diversity in SNP analysis. They also calculated the Faith phylogenetic diversity (FPD) index and the average pairwise distance (MPD) of 203 genomes from the entire latest dataset and 130 genomes from branches 1-4 to the present. I calculated the amount. Yersinia pestis Branch 1–4 Genetic diversity derived from polytomy. Scientists have raised the possibility of local emergence in connection with the introduction of the BSK001 / 003 strain into the Chui Valley from another region to solve the current hypothesis of the geographic origin of the plague pandemic. I looked it up.

A scientifically accurate 3D illustration showing the structure of cells containing Yersinia pestis, DNA, plasmids and ribosomes. Image Credit: Kateryna Kon / Shutterstock

Results and conclusions

Current analysis of historical, ancient, and archaeological genomic evidence by Yersinia pestis Yersinia pestis I was involved in a pandemic of black death.The latest shared ancestors of prominent diversification are generally associated with pandemic developments, dating back to the first half of 14 here.^th Identified as two reconstructed ancient times in the century Yersinia pestis Genomes forming a single strain (BSK003 and BSK001).

The local awakening of the restored ancient sequence, Yersinia pestis A reservoir in the wider Tianshan area. Current data support the cause of the second plague pandemic in Central Eurasia in early 2014.^th It is based on various evidences of the century.

Overall, current research presents ancient times Yersinia pestis 14 Evidence from Central Eurasia suggesting^th-The Occurrence of the Century; Therefore, the attribution of previous outbreaks requires further investigation. Currently, the focused sampling of this study cannot assess the spread of the BSK003 / 001 strain.Previous analysis shows that Yersinia pestis It can spread rapidly without accumulating genetic variation, allowing the same sequence to co-exist over a large geographic area.

Current studies do not provide evidence to speculate on the link between environmental factors and the Karajgach epidemic. However, the authors believe that the new exact 1338-1339 dates will be a benchmark for future archaeological, environmental and historical studies focused on the incident that caused them. Yersinia pestis Caused the emergence of humans and the second plague pandemic.

Scientists point out that past and present experience shows that identifying the cause of a pandemic is a difficult task and cannot be completed in a single scientific discipline.Although it is ancient Yersinia pestis The genome revealed in this publication provided biological data to resolve old controversies, and the scope and value of current research was defined by clear historical and archaeological contexts. As a result, the team hopes that future synergies will provide important information for the complete restructuring of the dynamics that led to the second plague pandemic.