Browsing by Subject "Microbiome"

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  • Ottman, Noora; Geerlings, Sharon Y.; Aalvink, Steven; de Vos, Willem M.; Belzer, Clara (2017)
    The discovery of Akkermansia muciniphila has opened new avenues for the use of this abundant intestinal symbiont in next generation therapeutic products, as well as targeting microbiota dynamics. A. muciniphila is known to colonize the mucosal layer of the human intestine where it triggers both host metabolic and immune responses. A. muciniphila is particularly effective in increasing mucus thickness and increasing gut barrier function. As a result host metabolic markers ameliorate. The mechanism of host regulation is thought to involve the outer membrane composition, including the type IV pili of A. muciniphila, that directly signal to host immune receptors. At the same time the metabolic activity of A. muciniphila leads to the production of short chain fatty acids that are beneficial to the host and microbiota members. This contributes to host-microbiota and microbe-microbe syntrophy The mucolytic activity and metabolite production make A. muciniphila a key species in the mucus layer, stimulating beneficial mucosal microbial networks. This well studied member of the microbiota has been studied in three aspects that will be further described in this review: i) A. muciniphila characteristics and mucin adaptation, ii) its role as key species in the mucosal microbiome, and iii) its role in host health. (C) 2017 Published by Elsevier Ltd.
  • Schwarz, Emanuel; Maukonen, Johanna; Hyytiäinen, Tiina; Kieseppä, Tuula; Oresic, Matej; Sabunciyan, Sarven; Mantere, Outi; Saarela, Maria; Yolken, Robert; Suvisaari, Jaana (2018)
    The effects of gut microbiota on the central nervous system, along its possible role in mental disorders, have received increasing attention. Here we investigated differences in fecal microbiota between 28 patients with first-episode psychosis (FEP) and 16 healthy matched controls and explored whether such differences were associated with response after up to 12 months of treatment. Numbers of Lactobacillus group bacteria were elevated in FEP-patients and significantly correlated with severity along different symptom domains. A subgroup of FEP patients with the strongest microbiota differences also showed poorer response after up to 12 months of treatment. The present findings support the involvement of microbiota alterations in psychotic illness and may provide the basis for exploring the benefit of their modulation on treatment response and remission. (C) 2017 Elsevier B.V. All rights reserved.
  • Swann, J. R.; Rajilic-Stojanovic, M.; Salonen, A.; Sakwinska, O.; Gill, C.; Meynier, A.; Fanca-Berthon, P.; Schelkle, B.; Segata, N.; Shortt, C.; Tuohy, K.; Hasselwander, O. (2020)
    With the growing appreciation for the influence of the intestinal microbiota on human health, there is increasing motivation to design and refine interventions to promote favorable shifts in the microbiota and their interactions with the host. Technological advances have improved our understanding and ability to measure this indigenous population and the impact of such interventions. However, the rapid growth and evolution of the field, as well as the diversity of methods used, parameters measured and populations studied, make it difficult to interpret the significance of the findings and translate their outcomes to the wider population. This can prevent comparisons across studies and hinder the drawing of appropriate conclusions. This review outlines considerations to facilitate the design, implementation and interpretation of human gut microbiota intervention studies relating to foods based upon our current understanding of the intestinal microbiota, its functionality and interactions with the human host. This includes parameters associated with study design, eligibility criteria, statistical considerations, characterization of products and the measurement of compliance. Methodologies and markers to assess compositional and functional changes in the microbiota, following interventions are discussed in addition to approaches to assess changes in microbiota-host interactions and host responses. Last, EU legislative aspects in relation to foods and health claims are presented. While it is appreciated that the field of gastrointestinal microbiology is rapidly evolving, such guidance will assist in the design and interpretation of human gut microbiota interventional studies relating to foods.
  • Chia, Loo Wee; Hornung, Bastian V. H.; Aalvink, Steven; Schaap, Peter J.; de Vos, Willem M.; Knol, Jan; Belzer, Clara (2018)
    Host glycans are paramount in regulating the symbiotic relationship between humans and their gut bacteria. The constant flux of host-secreted mucin at the mucosal layer creates a steady niche for bacterial colonization. Mucin degradation by keystone species subsequently shapes the microbial community. This study investigated the transcriptional response during mucin-driven trophic interaction between the specialised mucin-degrader Akkermansia muciniphila and a butyrogenic gut commensal Anaerostipes caccae. A. muciniphila monocultures and co-cultures with non-mucolytic A. caccae from the Lachnospiraceae family were grown anaerobically in minimal media supplemented with mucin. We analysed for growth, metabolites (HPLC analysis), microbial composition (quantitative reverse transcription PCR), and transcriptional response (RNA-seq). Mucin degradation by A. muciniphila supported the growth of A. caccae and concomitant butyrate production predominantly via the acetyl-CoA pathway. Differential expression analysis (DESeq 2) showed the presence of A. caccae induced changes in the A. muciniphila transcriptional response with increased expression of mucin degradation genes and reduced expression of ribosomal genes. Two putative operons that encode for uncharacterised proteins and an efflux system, and several two-component systems were also differentially regulated. This indicated A. muciniphila changed its transcriptional regulation in response to A. caccae. This study provides insight to understand the mucin-driven microbial ecology using metatranscriptomics. Our findings show that the expression of mucolytic enzymes by A. muciniphila increases upon the presence of a community member. This could indicate its role as a keystone species that supports the microbial community in the mucosal environment by increasing the availability of mucin sugars.
  • Gerritsen, Jacoline; Hornung, Bastian; Renckens, Bernadette; van Hijum, Sacha A. F. T.; dos Santos, Vitor A. P. Martins; Rijkers, Ger T.; Schaap, Peter J.; de Vos, Willem M.; Smidt, Hauke (2017)
    Background. The microbiota in the small intestine relies on their capacity to rapidly import and ferment available carbohydrates to survive in a complex and highly competitive ecosystem. Understanding how these communities function requires elucidating the role of its key players, the interactions among them and with their environment/host. Methods. The genome of the gut bacterium Romboutsia ilealis CRIBT was sequenced with multiple technologies (Illumina paired-end, mate-pair and PacBio). The transcriptome was sequenced (Illumina HiSeq) after growth on three different carbohydrate sources, and short chain fatty acids were measured via HPLC. Results. We present the complete genome of Romboutsia ilealis CRIBT, a natural inhabitant and key player of the small intestine of rats. R. ilealis CRIBT possesses a circular chromosome of 2,581,778 bp and a plasmid of 6,145 bp, carrying 2,351 and eight predicted protein coding sequences, respectively. Analysis of the genome revealed limited capacity to synthesize amino acids and vitamins, whereas multiple and partially redundant pathways for the utilization of different relatively simple carbohydrates are present. Transcriptome analysis allowed identification of the key components in the degradation of glucose, L-fucose and fructo-oligosaccharides. Discussion. This revealed that R. ilealis CRIBT is adapted to a nutrient-rich environment where carbohydrates, amino acids and vitamins are abundantly available.
  • Ventin-Holmberg, Rebecka (Helsingin yliopisto, 2019)
    Inflammatory bowel disease (IBD) is a globally increasing chronic disease, for which the pathogenesis still is unclear. The most common subtypes of IBD are Crohn’s disease (CD) and ulcerative colitis (UC). It is widely known that, in addition to the genetics, an altered immune response against the gut microbiome plays an important role in the development of the disease. For the IBD patients, to whom conventional medication is not sufficient, the TNF-α blocker infliximab, is given. However, about one third of the patients receiving infliximab treatment, do not respond to the drug, or lose response over time. Since there to this day are no reliable diagnostic markers available, the finding of such is of great importance. The goal of this study was to investigate possible markers for drug response in the gut mycobiota composition of IBD patients. The gut mycobiota composition of 72 IBD patients receiving infliximab was studied by MiSeq sequencing of fungal DNA from fecal samples, collected during one year. The sequencing data was analyzed using the mare package in R. In addition, anti-Saccharomyces cerevisiae antibody (ASCA) concentrations were measured from baseline serum samples by ELISA. Finally, calprotectin concentrations were measured from baseline and twelve weeks post infliximab serum samples by ELISA to study whether serum samples could be used instead of fecal samples for measuring calprotectin values. Results show an increase of the Candida and Spiromyces genera in the gut mycobiota of non-responding patients at baseline. At all timepoints, the Spiromyces genus was observed at a higher abundance, compared to the group of patients responding well or partially to the medication. Interestingly, the increase of Candida was seen only in Crohn’s disease patients, when looking at the composition at all timepoints. ASCA values did not differ between the response groups. The serum calprotectin values did not correlate with fecal calprotectin, and serum calprotectin can thus not be used as a marker of gut inflammation. In conclusion, the gut mycobiota can offer predictive markers for drug response prediction to infliximab in IBD patients, which can with further studies offer a clinical diagnostic tool for prediction of drug response.
  • Tuominen, Heidi; Rautava, Jaana; Kero, Katja; Syrjänen, Stina; Collado, Maria C; Rautava, Samuli (BioMed Central, 2021)
    Abstract Background Aberrant microbiota composition has been linked to disease development at numerous anatomical sites. Microbiota changes in reaction to viral infections, such as human papillomavirus (HPV), have been investigated almost exclusively in the female reproductive tract. However, HPV infection may also affect male health by reducing semen quality and fertility. The aim of this study was to investigate whether present HPV DNA is associated with detectable changes in semen bacterial microbiota composition and diversity. Methods This study relied on stored semen samples from 31 fertile healthy men who participated in the Finnish family HPV Study during the years 1998–2001. DNA was extracted from semen with PCR template preparation kit. HPV was genotyped using Luminex-based Multimetrix® assay. Microbiota was analyzed from the V3-V4 region of 16S rDNA gene following sequencing on an Illumina MiSeq platform. All statistical analyses were performed with Calypso software version 8.84. Results HPV DNA was detected in 19.4% (6/31) of the semen samples. HPV status in the semen did not impact the α-diversity estimations, as measured by Chao1 and Shannon indices, nor ß-diversity. Nevertheless, HPV-positive semen samples exhibited differences in the taxonomic composition of the bacterial microbiota including higher abundances of Moraxellaceae (p = 0.028), Streptococcus (p = 0.0058) and Peptostreptococcus (p = 0.012) compared to HPV-negative semen samples. Conclusion HPV infection is associated with altered bacterial microbiota composition in semen, and this might have in impact to male health in general. As of present, it is unclear whether these changes result from HPV infection or whether altered bacterial microbiota increases susceptibility to HPV infection. More research is needed on viral-bacterial interactions in the male reproductive system.
  • Muszer, Magdalena; Noszczynska, Magdalena; Kasperkiewicz, Katarzyna; Skurnik, Mikael (2015)
    The microorganisms that inhabit humans are very diverse on different body sites and tracts. Each specific niche contains a unique composition of the microorganisms that are important for a balanced human physiology. Microbial cells outnumber human cells by tenfold and they function as an invisible organ that is called the microbiome. Excessive use of antibiotics and unhealthy diets pose a serious danger to the composition of the microbiome. An imbalance in the microbial community may cause pathological conditions of the digestive system such as obesity, cancer and inflammatory bowel disease; of the skin such as atopic dermatitis, psoriasis and acne and of the cardiovascular system such as atherosclerosis. An unbalanced microbiome has also been associated with neurodevelopmental disorders such as autism and multiple sclerosis. While the microbiome has a strong impact on the development of the host immune system, it is suspected that it can also be the cause of certain autoimmune diseases, including diabetes or rheumatoid arthritis. Despite the enormous progress in the field, the interactions between the human body and its microbiome still remain largely unknown. A better characterization of the interactions may allow for a deeper understanding of human disease states and help to elucidate a possible association between the composition of the microbiome and certain pathologies. This review focuses on general findings that are related to the area and provides no detailed information about the case of study. The aim is to give some initial insight on the studies of the microbiome and its connection with human health.
  • Jalanka, Jonna; Mattila, Eero; Jouhten, Hanne; Hartman, Jorn; de Vos, Willem M; Arkkila, Perttu; Satokari, Reetta (BioMed Central, 2016)
    Abstract Background Faecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infection (rCDI). It restores the disrupted intestinal microbiota and subsequently suppresses C. difficile. The long-term stability of the intestinal microbiota and the recovery of mucosal microbiota, both of which have not been previously studied, are assessed herein. Further, the specific bacteria behind the treatment efficacy are also investigated. Methods We performed a high-throughput microbiota profiling using a phylogenetic microarray analysis of 131 faecal and mucosal samples from 14 rCDI patients pre- and post-FMT during a 1-year follow-up and 23 samples from the three universal donors over the same period. Results The FMT treatment was successful in all patients. FMT reverted the patients’ bacterial community to become dominated by Clostridium clusters IV and XIVa, the major anaerobic bacterial groups of the healthy gut. In the mucosa, the amount of facultative anaerobes decreased, whereas Bacteroidetes increased. Post-FMT, the patients’ microbiota profiles were more similar to their own donors than what is generally observed for unrelated subjects and this striking similarity was retained throughout the 1-year follow-up. Furthermore, the universal donor approach allowed us to identify bacteria commonly established in all CDI patients and revealed a commonly acquired core microbiota consisting of 24 bacterial taxa. Conclusions FMT induces profound microbiota changes, therefore explaining the high clinical efficacy for rCDI. The identification of commonly acquired bacteria could lead to effective bacteriotherapeutic formulations. FMT can affect microbiota in the long-term and offers a means to modify it relatively permanently for the treatment of microbiota-associated diseases.
  • Jalanka, Jonna; Mattila, Eero; Jouhten, Hanne; Hartman, Jorn; de Vos, Willem M.; Arkkila, Perttu; Satokari, Reetta (2016)
    Background: Faecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infection (rCDI). It restores the disrupted intestinal microbiota and subsequently suppresses C. difficile. The long-term stability of the intestinal microbiota and the recovery of mucosal microbiota, both of which have not been previously studied, are assessed herein. Further, the specific bacteria behind the treatment efficacy are also investigated. Methods: We performed a high-throughput microbiota profiling using a phylogenetic microarray analysis of 131 faecal and mucosal samples from 14 rCDI patients pre- and post-FMT during a 1-year follow-up and 23 samples from the three universal donors over the same period. Results: The FMT treatment was successful in all patients. FMT reverted the patients' bacterial community to become dominated by Clostridium clusters IV and XIVa, the major anaerobic bacterial groups of the healthy gut. In the mucosa, the amount of facultative anaerobes decreased, whereas Bacteroidetes increased. Post-FMT, the patients' microbiota profiles were more similar to their own donors than what is generally observed for unrelated subjects and this striking similarity was retained throughout the 1-year follow-up. Furthermore, the universal donor approach allowed us to identify bacteria commonly established in all CDI patients and revealed a commonly acquired core microbiota consisting of 24 bacterial taxa. Conclusions: FMT induces profound microbiota changes, therefore explaining the high clinical efficacy for rCDI. The identification of commonly acquired bacteria could lead to effective bacteriotherapeutic formulations. FMT can affect microbiota in the long-term and offers a means to modify it relatively permanently for the treatment of microbiota-associated diseases.
  • Knip, Mikael; Honkanen, Jarno (2017)
    Purpose of Review The purpose of this review is to summarize potential modulations of the intestinal microbiome aimed at preventing or delaying progression to overt type 1 diabetes in the light of recently identified perturbations of the gut microbiota associated with the development of type 1 diabetes. Recent Findings Accumulated data suggest that the gut microbiota is involved at two different steps in the evolution of type 1 diabetes. At the first step, the intestinal tract is colonized by a microbial community unable to provide an adequate education of the immune system. As a consequence, the infant acquires susceptibility to immune-mediated diseases, type 1 diabetes included. At the other step, the young child seroconverts to positivity for diabetes-associated autoantibodies. This is preceded or accompanied by a decrease in the diversity of the intestinal microbiota and an increased abundance of Bacteroides species. These changes will affect the disease process promoting progression toward overt type 1 diabetes. Summary By providing specific probiotics, one can affect the colonization of the intestinal tract in the newborn infant or strengthen the immune education in early life. Human milk oligosaccharides function as nutrients for "healthy" bacteria. Dietary interventions applying modified starches can influence the numbers and activities of both autoreactive and regulatory T cells and provide protection against autoimmune diabetes in non-obese diabetic mice. Modulation of the intestinal microbiome holds the promise of effective protection against human type 1 diabetes.
  • van der Ark, Kees C. H.; van Heck, Ruben G. A.; Dos Santos, Vitor A. P. Martins; Belzer, Clara; de Vos, Willem M. (2017)
    The human gut is colonized with a myriad of microbes, with substantial interpersonal variation. This complex ecosystem is an integral part of the gastrointestinal tract and plays a major role in the maintenance of homeostasis. Its dysfunction has been correlated to a wide array of diseases, but the understanding of causal mechanisms is hampered by the limited amount of cultured microbes, poor understanding of phenotypes, and the limited knowledge about interspecies interactions. Genome-scale metabolic models (GEMs) have been used in many different fields, ranging from metabolic engineering to the prediction of interspecies interactions. We provide showcase examples for the application of GEMs for gut microbes and focus on (i) the prediction of minimal, synthetic, or defined media; (ii) the prediction of possible functions and phenotypes; and (iii) the prediction of interspecies interactions. All three applications are key in understanding the role of individual species in the gut ecosystem as well as the role of the microbiota as a whole. Using GEMs in the described fashions has led to designs of minimal growth media, an increased understanding of microbial phenotypes and their influence on the host immune system, and dietary interventions to improve human health. Ultimately, an increased understanding of the gut ecosystem will enable targeted interventions in gut microbial composition to restore homeostasis and appropriate host-microbe crosstalk.
  • Hugenholtz, Floor; de Vos, Willem M. (2018)
    Since the early days of the intestinal microbiota research, mouse models have been used frequently to study the interaction of microbes with their host. However, to translate the knowledge gained from mouse studies to a human situation, the major spatio-temporal similarities and differences between intestinal microbiota in mice and humans need to be considered. This is done here with specific attention for the comparative physiology of the intestinal tract, the effect of dietary patterns and differences in genetics. Detailed phylogenetic and metagenomic analysis showed that while many common genera are found in the human and murine intestine, these differ strongly in abundance and in total only 4% of the bacterial genes are found to share considerable identity. Moreover, a large variety of murine strains is available yet most of the microbiota research is performed in wild-type, inbred strains and their transgenic derivatives. It has become increasingly clear that the providers, rearing facilities and the genetic background of these mice have a significant impact on the microbial composition and this is illustrated with recent experimental data. This may affect the reproducibility of mouse microbiota studies and their conclusions. Hence, future studies should take these into account to truly show the effect of diet, genotype or environmental factors on the microbial composition.
  • Pereira, Pedro A. B.; Aho, Velma T. E.; Paulin, Lars; Pekkonen, Eero; Auvinen, Petri; Scheperjans, Filip (2017)
    Introduction: Parkinson's disease (PD) is associated with neuropathological changes in olfactory and gastrointestinal tissues, and PD patients frequently suffer from hyposmia, hyposalivation, and dysphagia. Since hyposmia and gastrointestinal dysfunction are frequently premotor symptoms, it has been speculated that an external, for example microbial, agent could trigger the pathologic process in the corresponding organs, subsequently spreading to the central nervous system. We recently showed evidence for compositional differences between the fecal microbiota of PD patients and control subjects. In this study, our objective was to explore a possible connection between nasal and oral microbiota and PD. Methods: We compared the oral and nasal bacterial communities of PD patients (oral: n = 72, nasal: n = 69) and control subjects (oral: n = 76, nasal: n = 67) using a 16S rRNA gene amplicon sequencing approach. Results: Oral and nasal microbiota differed markedly from each other, with no notable similarity within subjects. Oral microbiota of PD patients and control subjects had differences in beta diversity and abundances of individual bacterial taxa. An increase in the abundance of opportunistic oral pathogens was detected in males, both with and without PD. Our data did not reveal convincing differences between the nasal microbiota of control subjects and PD patients. Conclusion: The oral microbiome deserves additional research regarding its connection to PD and its biomarker potential. The higher abundance of oral pathogens in men underlines the importance of monitoring and promoting male dental health. (C) 2017 Elsevier Ltd. All rights reserved.
  • Santos-Cortez, R.L.P.; Bhutta, M.F.; Earl, J.P.; Hafrén, Lena; Jennings, M.; Mell, J.C.; Pichichero, M.E.; Ryan, A.F.; Tateossian, Hilda; Ehrlich, G.D. (2020)
    Objective: To review the most recent advances in human and bacterial genomics as applied to pathogenesis and clinical management of otitis media. Data sources: PubMed articles published since the last meeting in June 2015 up to June 2019. Review methods: A panel of experts in human and bacterial genomics of otitis media was formed. Each panel member reviewed the literature in their respective fields and wrote draft reviews. The reviews were shared with all panel members, and a merged draft was created. The panel met at the 20th International Symposium on Recent Advances in Otitis Media in June 2019, discussed the review and refined the content. A final draft was made, circulated, and approved by the panel members. Conclusion: Trans-disciplinary approaches applying pan-omic technologies to identify human susceptibility to otitis media and to understand microbial population dynamics, patho-adaptation and virulence mechanisms are crucial to the development of novel, personalized therapeutics and prevention strategies for otitis media. Implications for practice: In the future otitis media prevention strategies may be augmented by mucosal immunization, combination vaccines targeting multiple pathogens, and modulation of the middle ear microbiome. Both treatment and vaccination may be tailored to an individual's otitis media phenotype as defined by molecular profiles obtained by using rapidly developing techniques in microbial and host genomics. © 2020 Elsevier B.V.
  • Kolmeder, Carolin A.; de Vos, Willem M. (2021)
    It is known for more than 100 years that the intestinal microbes are important for the host's health and the last decade this is being intensely studied with a focus on the mechanistic aspects. Among the fundamental functions of the intestinal microbiome are the priming of the immune system, the production of essential vitamins and the energy harvest from foods. By now, several dozens of diseases, both intestinal and non-intestinal related, have been associated with the intestinal microbiome. Initially, this was based on the description of the composition between groups of different health status or treatment arms based on phylogenetic approaches based on the 16S rRNA gene sequences. This way of analysis has mostly moved to the analysis of all the genes or transcripts of the microbiome i.e. metagenomics and meta-transcriptomics. Differences are regularly found but these have to be taken with caution as we still do not know what the majority of genes of the intestinal microbiome are capable of doing. To circumvent this caveat researchers are studying the proteins and the metabolites of the microbiome and the host via metaproteomics and metabolomics approaches. However, also here the complexity is high and only a fraction of signals obtained with high throughput instruments can be identified and assigned to a known protein or molecule. Therefore, modern microbiome research needs advancement of existing and development of new analytical techniques. The usage of model systems like intestinal organoids where samples can be taken and processed rapidly as well as microfluidics systems may help. This review aims to elucidate what we know about the functionality of the human intestinal microbiome, what technologies are advancing this knowledge, and what innovations are still required to further evolve this actively developing field. (C) 2020 The Authors. Published by Elsevier B.V.
  • Ventura, Marco; O'Toole, Paul W.; de Vos, Willem M.; van Sinderen, Douwe (2018)
    The gut microbiota represents a highly complex assembly of microbes, which interact with each other and with their host. These interactions have various implications in terms of health and disease, and this multi-author review issue will address a number of selected aspects pertaining to gut microbiota research.
  • Pulkkinen, Essi (Helsingin yliopisto, 2019)
    The Baltic Sea is a geologically and biologically unique sea highly vulnerable to environmental hazards, and the most emphasized threat is the risk of oil spills. The microbiology of the Baltic Sea has not been extensively studied, and most studies have focused on bacteria, leaving archaea and fungi to less attention. In addition to the natural microbial communities of different parts of the Baltic Sea, the effects of diesel oil, and dispersants applied in case of an oil spill, on these microbial communities is yet to be elucidated. The focus of this Master’s thesis was to compare the bacterial, archaeal and fungal community compositions of the Baltic Sea surface water at three distinct locations; the open sea, a pristine archipelago, and putatively oil contaminated coastal water at an oil refinery. In addition, the short-term effects of diesel oil and dispersant on the three locations were studied during a 72-hour microcosm experiment. Next-generation Ion Torrent sequencing of bacterial V3–V4 and archaeal V4 regions of 16S rDNA and fungal ITS regions was used for a community composition analysis. Quantitative polymerase chain reaction (qPCR) was applied to determine the changes in the copy numbers of bacterial 16S rRNA genes and two genes associated with microbial hydrocarbon degradation, i.e. ring-hydroxylating dioxygenases (RHD) and alkane hydroxylases (AlkB). Based on the findings, the three sites under investigation harbored differing surface water microbiomes demonstrating differing responses to diesel and dispersant amendments, and furthermore, the results indicate that the putatively oil contaminated coastal site has higher natural petroleum hydrocarbon degradation potential compared to the pristine archipelago and especially the open sea. It is noteworthy, that over 90% of the fungal sequences from the open sea and the pristine archipelago, and over half of the fungal sequences from the putatively oil contaminated coastal site were unidentified even at phylum level. In addition, almost half of the archaeal sequences from the putatively oil contaminated site were unindentified. Assessing the petroleum hydrocarbon degradation potential of the indigenous microbiome in different parts of the Baltic Sea is of great importance, since the data can potentially be utilized when developing suitable biological oil spill response methods as well as predicting the rates of petroleum hydrocarbon degradation in different parts of the Baltic Sea area.