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In the grave environment, microorganisms are major ecological participants in the successional decomposition of vertebrates and could infiltrate the skeleton/skeletal material during taphonomic processes. The diversity of archaeological skeleton-associated microbial assemblages and the impact of various factors are poorly understood. This study aimed to evaluate the taxonomic microbial composition of archaeological human bone and teeth samples from the 7th to 11th centuries AD from two burial sites in Latvia. Samples were analysed by a shotgun metagenomics-based approach. The results showed a strong presence of the environmental DNA in the samples, and variability in microbial community structure between individual samples. Differences in microbial composition were observed between bone and tooth samples, as well as between different burial sites. Furthermore, the presence of endogenous ancient DNA (aDNA) in tooth samples was detected. Overall, compositions of microbial communities associated with archaeological human remains in Latvia dated 7-11th century AD were influenced by the sample type and burial location. These findings indicate that, while the content of historical DNA in archaeological samples is low, the comparison of archaeological skeleton-associated microbial assemblages across time and space, along with aDNA damage profile analysis, is important and could help to reveal putative ancient microorganisms., (© 2023 The Authors. Environmental Microbiology Reports published by Applied Microbiology International and John Wiley & Sons Ltd.)

Natural sciences provide several modern methodologies that could be successfully applied in archaeological studies. In this pilot study, archaeological human remains from two Iron Age cemeteries (7th-twelfth centuries AD), Lejasbitēni and Čunkāni-Dreņģeri, which are located in different regions of Latvia, were studied. We applied ancient DNA (aDNA) and tooth enamel peptide analysis to determine the biological sex of the individuals. In addition, aDNA analysis was used to perform mtDNA haplogroup analysis. In most cases, the results of aDNA analysis regarding the biological sex of individuals coincided with the gender assigned based on grave orientation and grave goods. The results of sex determination using peptide analysis in all four individuals for whom data were available matched the possible gender. Of the 17 samples that had sufficient DNA for sequencing, seven samples had enough reads to perform mtDNA haplogroup analysis. The H2a2a, I4a1, H2a2a1, and H16c mtDNA haplogroups were identified in the individuals from the Lejasbitēni cemetery, while the T2b and K1a + 150 mtDNA haplogroups were identified in the individuals from the Čunkāni-Dreņģeri cemetery. Overall, the obtained results demonstrated the feasibility of applying aDNA and tooth enamel peptide analysis for biological sex determination within archaeological studies. The availability of human aDNA data will be highly useful for investigating the demographic history and social structures in Iron Age Latvia., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

A 5,000-year-old Yersinia pestis genome (RV 2039) is reconstructed from a hunter-fisher-gatherer (5300-5050 cal BP) buried at Riņņukalns, Latvia. RV 2039 is the first in a series of ancient strains that evolved shortly after the split of Y. pestis from its antecessor Y. pseudotuberculosis ∼7,000 years ago. The genomic and phylogenetic characteristics of RV 2039 are consistent with the hypothesis that this very early Y. pestis form was most likely less transmissible and maybe even less virulent than later strains. Our data do not support the scenario of a prehistoric pneumonic plague pandemic, as suggested previously for the Neolithic decline. The geographical and temporal distribution of the few prehistoric Y. pestis cases reported so far is more in agreement with single zoonotic events., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Recent advantages in paleomicrobiology have provided an opportunity to investigate the composition of ancient microbial ecologies. Here, using metagenome analysis, we investigated the microbial profiles of historic dental calculus retrieved from archaeological human remains from postmedieval Latvia dated 16-17th century AD and examined the associations of oral taxa and microbial diversity with specific characteristics. We evaluated the preservation of human oral microbiome patterns in historic samples and compared the microbial composition of historic dental calculus, modern human dental plaque, modern human dental calculus samples and burial soil microbiota. Overall, the results showed that the majority of microbial DNA in historic dental calculus originated from the oral microbiome with little impact of the burial environment. Good preservation of ancient DNA in historical dental calculus samples has provided reliable insight into the composition of the oral microbiome of postmedieval Latvian individuals. The relative stability of the classifiable oral microbiome composition was observed. Significant differences between the microbiome profiles of dental calculus and dental plaque samples were identified, suggesting microbial adaptation to a specific human body environment.