Comprehensive analysis of microorganisms accompanying human archaeological remains

Exploring correlations between gut mycobiome and lymphocytes in melanoma patients undergoing anti-PD-1 therapy

Research has shown that the microbiome can influence how the immune system responds to melanoma cells, affecting the course of the disease and the outcome of the therapy. Here, we used the metagenomic approach and flow cytometry analyses of blood cells to discover correlations between gut fungi of metastatic melanoma patients enrolled in anti-PD-1 therapy and lymphocytes in their blood.We analyzed the patterns of associations before the first administration of anti-PD-1 therapy (BT, n = 61) and in the third month of the therapy (T3, n = 37), allowing us to track changes during treatment. To understand the possible impact of gut fungi on the efficacy of anti-PD-1 therapy, we analyzed the associations in clinical beneficiaries (CB, n = 37) and non-beneficiaries (NB, n = 24), as well as responders (R, n = 28) and non-responders (NR, n = 33).Patients with LDH < 338 units/L, overall survival (OS) > 12, CB, as well as R, had lower levels of Shannon diversity (p = 0.02, p = 0.05, p = 0.05, and p = 0.03, respectively). We found that the correlation pattern between intestinal fungi and lymphocytes was specific to the type of response, positive or negative. When comparing CB and NB groups, correlations with opposite directions were detected for C. albicans, suggesting a response-specific immune reaction. For CB, M. restricta exhibited a set of correlations with different types of lymphocytes, with prevalent positive correlations, suggesting a robust immune response in the CB group. This result extends our former research, where M. restricta and C. albicans were associated with an increased risk of melanoma progression and a poorer response to anti-PD-1 treatment.

Insight into the microbial diversity and community in the sacrificial pits of Sanxingdui site (Sichuan, China)

Introduction

The Sanxingdui site (Sichuan, China) is the typical representative of the ancient Shu culture, which lasts from the late Neolithic to early Western Zhou. The sacrificial pits are located in the core region of Sanxingdui site, and numerous artifacts are unearthed including ivory, seashells, bronzes, pottery, jade, stone, gold, bone, and horn products. The function of the pits and buried artifacts has always been the focus, but the microbiome around artifacts attracts less attention. Recently, the microbiome in buried ivory soil has just been identified; however, the microbiome around other artifacts has never been studied. In term of the unique perspective for interpretation the archaeological issues, the study was carried out for: (1) the microbial diversity and community of soil in the lower layer of artifacts in sacrificial pits, (2) the potential biodeterioration behavior of organic and inorganic relics, and (3) the impact of sacrificial and burial activities in different sacrificial pits on microbiome.

Methods

There were 45 soil samples around different artifacts in three sacrificial pits and 12 raw soil samples inside or outside the sacrificial pit sampling from Sanxingdui site. The microbial genomes were then identified and analyzed using the next-generation high-throughput sequencing.

Results

The represented bacterial phyla were Proteobacteria, Actinobacteriota, GAL15, Chloroflexi, Acidobacteriota, Methylomirabilota, Thermoplasmatota, Crenarchaeota, Gemmatimonadota, and Firmicutes, and the represented fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota. Further microbial functional analysis found that the bacterial genera Sphingopyxis, Limnobacter, and Streptomyces and the fungal genera Cladosporium, Acremonium, and Mortierella were concerned with the degradation of organic matter, while the genera Pseudomonas, Arthrobacter, Variovorax, Aspergillus, and Penicillium might be related to the biocorrosion of bronzes. In addition, the microbial composition and principal co-ordinate analysis (PCoA) demonstrated the significant differences in microbial composition and structure between the raw soil samples and the soil samples around the artifacts and also between the soil samples in different sacrificial pits.

Discussion

It is important to understand the biodeterioration of the buried artifacts and the sacrificial activities in Sanxingdui site according to the results of microbial diversity and community. The combination of microbiology and archaeology will shed light on the archaeological issues related to the ancient human activities and behaviors.

Methanobrevibacter smithii cell variants in human physiology and pathology: A review

Methanobrevibacter smithii (M. smithii), initially isolated from human feces, has been recognised as a distinct taxon within the Archaea domain following comprehensive phenotypic, genetic, and genomic analyses confirming its uniqueness among methanogens. Its diversity, encompassing 15 genotypes, mirrors that of biotic and host-associated ecosystems in which M. smithii plays a crucial role in detoxifying hydrogen from bacterial fermentations, converting it into mechanically expelled gaseous methane. In microbiota in contact with host epithelial mucosae, M. smithii centres metabolism-driven microbial networks with Bacteroides, Prevotella, Ruminococcus, Veillonella, Enterococcus, Escherichia, Enterobacter, Klebsiella, whereas symbiotic association with the nanoarchaea Candidatus Nanopusillus phoceensis determines small and large cell variants of M. smithii. The former translocate with bacteria to induce detectable inflammatory and serological responses and are co-cultured from blood, urine, and tissular abscesses with bacteria, prototyping M. smithii as a model organism for pathogenicity by association. The sources, mechanisms and dynamics of in utero and lifespan M. smithii acquisition, its diversity, and its susceptibility to molecules of environmental, veterinary, and medical interest still have to be deeply investigated, as only four strains of M. smithii are available in microbial collections, despite the pivotal role this neglected microorganism plays in microbiota physiology and pathologies.

Gut Mycobiota Dysbiosis Is Associated with Melanoma and Response to Anti-PD-1 Therapy

Recent research indicates that gut microbiota may be vital in the advancement of melanoma. In this study, we found that melanoma patients exhibited a distinct gut mycobiota structure compared with healthy participants. Candida albicans, Candida dubliniensis, and Neurospora crassa were more abundant in samples from patients with melanoma, whereas Saccharomyces cerevisiae and Debaryomyces hansenii were less abundant. During anti-PD-1 treatment, the relative amount of Malassezia restricta and C. albicans increased. A higher level of Saccharomyces paradoxus was associated with a positive response to anti-PD-1 treatment, whereas a higher level of Tetrapisispora blattae was associated with a lack of clinical benefits. High levels of M. restricta and C. albicans, elevated serum lactate dehydrogenase, and being overweight were linked to increased risk of melanoma progression and poorer response to anti-PD-1 treatment. Thus, this study has revealed melanoma-associated mycobiome dysbiosis, characterized by altered fungal composition and fungi species associated with a higher risk of melanoma progression, identifying a role for the gut mycobiome in melanoma progression.

Ancient Genomes From Bronze Age Remains Reveal Deep Diversity and Recent Adaptive Episodes for Human Oral Pathobionts

Ancient microbial genomes can illuminate pathobiont evolution across millenia, with teeth providing a rich substrate. However, the characterization of prehistoric oral pathobiont diversity is limited. In Europe, only preagricultural genomes have been subject to phylogenetic analysis, with none compared to more recent archaeological periods. Here, we report well-preserved microbiomes from two 4,000-year-old teeth from an Irish limestone cave. These contained bacteria implicated in periodontitis, as well as Streptococcus mutans, the major cause of caries and rare in the ancient genomic record. Despite deriving from the same individual, these teeth produced divergent Tannerella forsythia genomes, indicating higher levels of strain diversity in prehistoric populations. We find evidence of microbiome dysbiosis, with a disproportionate quantity of S. mutans sequences relative to other oral streptococci. This high abundance allowed for metagenomic assembly, resulting in its first reported ancient genome. Phylogenetic analysis indicates major postmedieval population expansions for both species, highlighting the inordinate impact of recent dietary changes. In T. forsythia, this expansion is associated with the replacement of older lineages, possibly reflecting a genome-wide selective sweep. Accordingly, we see dramatic changes in T. forsythia's virulence repertoire across this period. S. mutans shows a contrasting pattern, with deeply divergent lineages persisting in modern populations. This may be due to its highly recombining nature, allowing for maintenance of diversity through selective episodes. Nonetheless, an explosion in recent coalescences and significantly shorter branch lengths separating bacteriocin-carrying strains indicate major changes in S. mutans demography and function coinciding with sugar popularization during the industrial period.

Benchmarking Metagenomic Classifiers on Simulated Ancient and Modern Metagenomic Data

Taxonomic profiling of ancient metagenomic samples is challenging due to the accumulation of specific damage patterns on DNA over time. Although a number of methods for metagenome profiling have been developed, most of them have been assessed on modern metagenomes or simulated metagenomes mimicking modern metagenomes. Further, a comparative assessment of metagenome profilers on simulated metagenomes representing a spectrum of degradation depth, from the extremity of ancient (most degraded) to current or modern (not degraded) metagenomes, has not yet been performed. To understand the strengths and weaknesses of different metagenome profilers, we performed their comprehensive evaluation on simulated metagenomes representing human dental calculus microbiome, with the level of DNA damage successively raised to mimic modern to ancient metagenomes. All classes of profilers, namely, DNA-to-DNA, DNA-to-protein, and DNA-to-marker comparison-based profilers were evaluated on metagenomes with varying levels of damage simulating deamination, fragmentation, and contamination. Our results revealed that, compared to deamination and fragmentation, human and environmental contamination of ancient DNA (with modern DNA) has the most pronounced effect on the performance of each profiler. Further, the DNA-to-DNA (e.g., Kraken2, Bracken) and DNA-to-marker (e.g., MetaPhlAn4) based profiling approaches showed complementary strengths, which can be leveraged to elevate the state-of-the-art of ancient metagenome profiling.

Ancient Clostridium DNA and variants of tetanus neurotoxins associated with human archaeological remains

The analysis of microbial genomes from human archaeological samples offers a historic snapshot of ancient pathogens and provides insights into the origins of modern infectious diseases. Here, we analyze metagenomic datasets from 38 human archaeological samples and identify bacterial genomic sequences related to modern-day Clostridium tetani, which produces the tetanus neurotoxin (TeNT) and causes the disease tetanus. These genomic assemblies had varying levels of completeness, and a subset of them displayed hallmarks of ancient DNA damage. Phylogenetic analyses revealed known C. tetani clades as well as potentially new Clostridium lineages closely related to C. tetani. The genomic assemblies encode 13 TeNT variants with unique substitution profiles, including a subgroup of TeNT variants found exclusively in ancient samples from South America. We experimentally tested a TeNT variant selected from an ancient Chilean mummy sample and found that it induced tetanus muscle paralysis in mice, with potency comparable to modern TeNT. Thus, our ancient DNA analysis identifies DNA from neurotoxigenic C. tetani in archaeological human samples, and a novel variant of TeNT that can cause disease in mammals.

Host Factors Associated with Gut Mycobiome Structure

Recent studies revealed a significant role of the gut fungal community in human health. Here, we investigated the content and variation of gut mycobiota among subjects from the European population. We explored the interplay between gut fungi and various host-related sociodemographic, lifestyle, health, and dietary factors. The study included 923 participants. Fecal DNA samples were analyzed by whole-metagenome high-throughput sequencing. Subsequently, fungi taxonomic profiles were determined and accompanied by computational and statistical analyses of the association with 53 host-related factors. Fungal communities were characterized by a high prevalence of Saccharomyces, Candida, and Sporisorium. Ten factors were found to correlate significantly with the overall mycobiota variation. Most were diet related, including the consumption of chips, meat, sodas, sweetening, processed food, and alcohol, followed by age and marital status. Differences in α- and/or β-diversity were also reported for other factors such as body mass index (BMI), job type, autoimmunological diseases, and probiotics. Differential abundance analysis revealed fungal species that exhibited different patterns of changes under specific conditions. The human gut mycobiota is dominated by yeast, including Saccharomyces, Malassezia, and Candida. Although intervolunteer variability was high, several fungal species persisted across most samples, which may be evidence that a core gut mycobiota exists. Moreover, we showed that host-related factors such as diet, age, and marital status influence the variability of gut mycobiota. To our knowledge, this is the first large and comprehensive study of the European cohort in terms of gut mycobiota associations with such an extensive and differentiated host-related set of factors. IMPORTANCE The human gut is inhabited by many organisms, including bacteria and fungi, that may affect human health. However, research on human gut mycobiome is still rare. Moreover, the large European-based cohort study is missing. Here, we analyzed the first large European cohort in terms of gut mycobiota associations with a differentiated host-related set of factors. Our results showed that chips, meat, sodas, sweetening, processed food, beer, alcohol consumption, age, and marital status were associated with the variability of gut mycobiota. Moreover, our analysis revealed changes in abundances at the fungal species level for many investigated factors. Our results can suggest potentially valuable paths for further, narrowly focused research on gut mycobiome and its impact on human health. In the coming era of gut microbiome-based precision medicine, further research into the relationship between different mycobial structures and host-related factors may result in new preventive approaches or therapeutic procedures.

Functional biomes beyond the bacteriome in the oral ecosystem

Selective constraint and pressures upon the host tissues often signifies a beneficial microbiome in any species. In the context of oral microbiome this displays a healthy microbial cosmos resisting the colonization and helps in rendering protection. This review highlights the endeavors of the oral microbiome beyond the bacteriome encompassing virome, mycobiome, protozoa and archaeomes in maintaining the oral homeostasis in health and disease. Scientific data based on the peer-reviewed publications on the microbial communities of the oral microbiome were selected and collated from the scientific database collection sites of web of science (WOS), pubmed central, Inspec etc., from 2010 to 2021 using the search key words like oral microbiome, oral microbiota, oral virome, oral bacteriome, oral mycobiome and oral archaeome. Data excluded were from conference proceedings, abstracts and book chapters. The oral homeostasis in both the health and disease conditions, mostly is balanced by the unrevealed virome, mycobiome, oral protozoa and archaeome. The review documents the need to comprehend the diversity that prevails among the kingdoms in order to determine the specific role played by each domain. Oral microbiome is also a novel research arena to develop drug and targeted therapies to treat various oro-dental infections.

Ancient DNA diffuses from human bones to cave stones

Recent studies have demonstrated the potential to recover ancient human mitochondrial DNA and nuclear DNA from cave sediments. However, the source of such sedimentary ancient DNA is still under discussion. Here we report the case of a Bronze Age human skeleton, found in a limestone cave, which was covered with layers of calcite stone deposits. By analyzing samples representing bones and stone deposits from this cave, we were able to: i) reconstruct the full human mitochondrial genome from the bones and the stones (same haplotype); ii) determine the sex of the individual; iii) reconstruct six ancient bacterial and archaeal genomes; and finally iv) demonstrate better ancient DNA preservation in the stones than in the bones. Thereby, we demonstrate the direct diffusion of human DNA from bones into the surrounding environment and show the potential to reconstruct ancient microbial genomes from such cave deposits, which represent an additional paleoarcheological archive resource.

Badania kopalnego DNA – możliwości i ograniczenia

Ostatnie cztery dekady przyniosły znaczący rozwój archeologii molekularnej i badania nad kopalnym DNA (aDNA). Nowatorskie metody uwzględniają szeroki zakres badań, począwszy od sekwencjonowania niewielkich fragmentów mitochondrialnego DNA po wielkoskalowe badania całych populacji, łączące sekwencjonowanie genomów mitochondrialnych, genów podlegających doborowi naturalnemu, jak i całych genomów jądrowych. Postęp, zwłaszcza w dziedzinie technologii sekwencjonowania DNA, umożliwił pozyskanie informacji ze szczątków paleontologicznych i materiału archeologicznego, umożliwiając zbadanie związków filogenetycznych między wymarłymi i współczesnymi gatunkami. Dzięki zastosowaniu technologii sekwencjonowania nowej generacji możliwe stało się poznanie sekwencji DNA nie tylko bezpośrednio ze szczątków ludzkich lub zwierzęcych, ale także z osadów sedymentacyjnych z głębin jezior oraz jaskiń. W artykule przedstawiono możliwości i ograniczenia występujące w badaniach nad kopalnym DNA ludzi, zwierząt czy bakterii z podkreśleniem wkładu polskich badaczy w rozwój tej dziedziny nauki.

Components of a Neanderthal gut microbiome recovered from fecal sediments from El Salt

A comprehensive view of our evolutionary history cannot ignore the ancestral features of our gut microbiota. To provide some glimpse into the past, we searched for human gut microbiome components in ancient DNA from 14 archeological sediments spanning four stratigraphic units of El Salt Middle Paleolithic site (Spain), including layers of unit X, which has yielded well-preserved Neanderthal occupation deposits dating around 50 kya. According to our findings, bacterial genera belonging to families known to be part of the modern human gut microbiome are abundantly represented only across unit X samples, showing that well-known beneficial gut commensals, such as Blautia, Dorea, Roseburia, Ruminococcus, Faecalibacterium and Bifidobacterium already populated the intestinal microbiome of Homo since as far back as the last common ancestor between humans and Neanderthals.

Biodeteriogens Characterization and Molecular Analyses of Diverse Funeral Accessories from XVII Century

A historical crypt offers us a particular view of the conditions of some buried materials (in this case textiles) and the various biogenic phenomena to which they were subjected over the centuries. In addition, significant knowledge can come by studying the DNA of buried objects which allows the recognition of materials, but also to reveal some practice of the funeral ceremony. In this study, the deteriorating microbial communities colonizing various funeral textile items were identified and characterized using microscopic observation, cultivation, polymerase chain reaction (PCR) and sequencing, hydrolytic tests; and culture-independent analysis (high-throughput sequencing, MinION platform). Different PCR assays and consequent sequencing of amplicons were employed to recognize the animal origin of bodice reinforcements and the type of plant used to embellish the young girl. The analysis of ancient DNA (aDNA from animal and plant) was also completed by the application of high-throughput sequencing through Illumina platform. The combination of all these techniques permitted the identification of a complex microbiota composed by dangerous degradative microorganisms able to hydrolyze various organic substrates such as fibroin, keratin, and cellulose. Bacteria responsible for metal corrosion and bio-mineralization, and entomopathogenic and phytopathogenic fungi. The analysis of aDNA identified the animal component used in bodice manufacturing, the plant utilized as ornament and probably the season of this fatal event.

Microbial community types and signature-like soil bacterial patterns from fortified prehistoric hills of Thuringia (Germany)

16S rRNA profiling has been applied for the investigation of bacterial communities of surface soil samples from forest-covered areas of ten prehistorical ramparts from different parts of Thuringia. Besides the majority bacterial types that are present in all samples, there could be identified bacteria that are highly abundant in some places and absent or low abundant in others. These differences are mainly related to the acidity of substrate and distinguish the communities of lime stone hills from soils of sand/quartzite and basalt hills. Minority components of bacterial communities show partially large differences that cannot be explained by the pH of the soil or incidental effects, only. They reflect certain relations between the communities of different places and could be regarded as a kind of signature-like patterns. Such relations had also been found in a comparison of the data from ramparts with formerly studied 16S rRNA profiling from an iron-age burial field. The observations are supporting the idea that a part of the components of bacterial communities from soil samples reflect their ecological history and can be understood as the “ecological memory” of a place. Probably such memory effects can date back to prehistoric times and might assist in future interpretations of archaeological findings on the prehistoric use of a place, on the one hand. On the other hand, the genetic profiling of soils of prehistoric places contributes to the evaluation of anthropogenic effects on the development of local soil bacterial diversity.

Analysis of oral microbiome from fossil human remains revealed the significant differences in virulence factors of modern and ancient Tannerella forsythia

BACKGROUND

Recent advances in the next-generation sequencing (NGS) allowed the metagenomic analyses of DNA from many different environments and sources, including thousands of years old skeletal remains. It has been shown that most of the DNA extracted from ancient samples is microbial. There are several reports demonstrating that the considerable fraction of extracted DNA belonged to the bacteria accompanying the studied individuals before their death.

RESULTS

In this study we scanned 344 microbiomes from 1000- and 2000- year-old human teeth. The datasets originated from our previous studies on human ancient DNA (aDNA) and on microbial DNA accompanying human remains. We previously noticed that in many samples infection-related species have been identified, among them Tannerella forsythia, one of the most prevalent oral human pathogens. Samples containing sufficient amount of T. forsythia aDNA for a complete genome assembly were selected for thorough analyses. We confirmed that the T. forsythia-containing samples have higher amounts of the periodontitis-associated species than the control samples. Despites, other pathogens-derived aDNA was found in the tested samples it was too fragmented and damaged to allow any reasonable reconstruction of these bacteria genomes. The anthropological examination of ancient skulls from which the T. forsythia-containing samples were obtained revealed the pathogenic alveolar bone loss in tooth areas characteristic for advanced periodontitis. Finally, we analyzed the genetic material of ancient T. forsythia strains. As a result, we assembled four ancient T. forsythia genomes - one 2000- and three 1000- year-old. Their comparison with contemporary T. forsythia genomes revealed a lower genetic diversity within the four ancient strains than within contemporary strains. We also investigated the genes of T. forsythia virulence factors and found that several of them (KLIKK protease and bspA genes) differ significantly between ancient and modern bacteria.

CONCLUSIONS

In summary, we showed that NGS screening of the ancient human microbiome is a valid approach for the identification of disease-associated microbes. Following this protocol, we provided a new set of information on the emergence, evolution and virulence factors of T. forsythia, the member of the oral dysbiotic microbiome.

The Oral Archaeome: A Scoping Review

The Archaea domain was recognized as a separate phylogenetic lineage in the tree of life nearly 3 decades ago. It is now known as part of the human microbiome; however, given that its roles in oral sites are still poorly understood, this review aimed to establish the current level of evidence regarding archaea in the oral cavity to guide future research, providing insights on the present knowledge about the human oral archaeome. A scoping review was conducted with the PRISMA Extension for Scoping Reviews checklist. Five electronic databases were searched, as well as gray literature. Two independent reviewers performed the selection and characterization of the studies. Clinical studies were included when the target population consisted of humans of any age who were donors of samples from the oral cavity. A qualitative analysis was performed, based on the type of oral site and by considering the methods employed for archaeal identification and taxonomy, including the DNA extraction protocols, primers, and probes used. Fifty articles were included in the final scoping review, published from 1987 to 2019. Most studies sampled periodontal sites. Methanogens were the most abundant archaea in those sites, and their presence could be associated with other periodontal pathogens. No consistent relationship with different disease conditions was observed in studies that evaluated the microbiota surviving in endodontic sites. Few articles analyzed the presence of archaea in dental caries, saliva, or tongue microbiota, as well as in archaeologic samples, also showing a relationship with healthy microbiota. Archaea have been detected in different oral niches of individuals from diverse geographic locations and clinical conditions, suggesting potential roles in oral diseases. Methodological limitations may hamper our current knowledge about archaeal diversity and prevalence in oral samples, and future research with diversified methodological approaches may lead to a better comprehension of the human oral archaeome.

Goth migration induced changes in the matrilineal genetic structure of the central-east European population

For years, the issues related to the origin of the Goths and their early migrations in the Iron Age have been a matter of hot debate among archaeologists. Unfortunately, the lack of new independent data has precluded the evaluation of the existing hypothesis. To overcome this problem, we initiated systematic studies of the populations inhabiting the contemporary territory of Poland during the Iron Age. Here, we present an analysis of mitochondrial DNA isolated from 27 individuals (collectively called the Mas-VBIA group) excavated from an Iron Age cemetery (dated to the 2^nd-4^th century A.D.) attributed to Goths and located near Masłomęcz, eastern Poland. We found that Mas-VBIA has similar genetic diversity to present-day Asian populations and higher diversity than that of contemporary Europeans. Our studies revealed close genetic links between the Mas-VBIA and two other Iron Age populations from the Jutland peninsula and from Kowalewko, located in western Poland. We disclosed the genetic connection between the Mas-VBIA and ancient Pontic-Caspian steppe groups. Similar connections were absent in the chronologically earlier Kowalewko and Jutland peninsula populations. The collected results seem to be consistent with the historical narrative that assumed that the Goths originated in southern Scandinavia; then, at least part of the Goth population moved south through the territory of contemporary Poland towards the Black Sea region, where they mixed with local populations and formed the Chernyakhov culture. Finally, a fraction of the Chernyakhov population returned to the southeast region of present-day Poland and established the archaeological formation called the “Masłomęcz group”.

Differential preservation of endogenous human and microbial DNA in dental calculus and dentin

Dental calculus (calcified dental plaque) is prevalent in archaeological skeletal collections and is a rich source of oral microbiome and host-derived ancient biomolecules. Recently, it has been proposed that dental calculus may provide a more robust environment for DNA preservation than other skeletal remains, but this has not been systematically tested. In this study, shotgun-sequenced data from paired dental calculus and dentin samples from 48 globally distributed individuals are compared using a metagenomic approach. Overall, we find DNA from dental calculus is consistently more abundant and less contaminated than DNA from dentin. The majority of DNA in dental calculus is microbial and originates from the oral microbiome; however, a small but consistent proportion of DNA (mean 0.08 ± 0.08%, range 0.007–0.47%) derives from the host genome. Host DNA content within dentin is variable (mean 13.70 ± 18.62%, range 0.003–70.14%), and for a subset of dentin samples (15.21%), oral bacteria contribute > 20% of total DNA. Human DNA in dental calculus is highly fragmented, and is consistently shorter than both microbial DNA in dental calculus and human DNA in paired dentin samples. Finally, we find that microbial DNA fragmentation patterns are associated with guanine-cytosine (GC) content, but not aspects of cellular structure.

A mosaic genetic structure of the human population living in the South Baltic region during the Iron Age

Despite the increase in our knowledge about the factors that shaped the genetic structure of the human population in Europe, the demographic processes that occurred during and after the Early Bronze Age (EBA) in Central-East Europe remain unclear. To fill the gap, we isolated and sequenced DNAs of 60 individuals from Kowalewko, a bi-ritual cemetery of the Iron Age (IA) Wielbark culture, located between the Oder and Vistula rivers (Kow-OVIA population). The collected data revealed high genetic diversity of Kow-OVIA, suggesting that it was not a small isolated population. Analyses of mtDNA haplogroup frequencies and genetic distances performed for Kow-OVIA and other ancient European populations showed that Kow-OVIA was most closely linked to the Jutland Iron Age (JIA) population. However, the relationship of both populations to the preceding Late Neolithic (LN) and EBA populations were different. We found that this phenomenon is most likely the consequence of the distinct genetic history observed for Kow-OVIA women and men. Females were related to the Early-Middle Neolithic farmers, whereas males were related to JIA and LN Bell Beakers. In general, our findings disclose the mechanisms that could underlie the formation of the local genetic substructures in the South Baltic region during the IA.