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- Kennedy, K. M., et al.
(author)
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Questioning the fetal microbiome illustrates pitfalls of low-biomass microbial studies
- 2023
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 613:7945, s. 639-649
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Journal article (peer-reviewed)abstract
- Whether the human fetus and the prenatal intrauterine environment (amniotic fluid and placenta) are stably colonized by microbial communities in a healthy pregnancy remains a subject of debate. Here we evaluate recent studies that characterized microbial populations in human fetuses from the perspectives of reproductive biology, microbial ecology, bioinformatics, immunology, clinical microbiology and gnotobiology, and assess possible mechanisms by which the fetus might interact with microorganisms. Our analysis indicates that the detected microbial signals are likely the result of contamination during the clinical procedures to obtain fetal samples or during DNA extraction and DNA sequencing. Furthermore, the existence of live and replicating microbial populations in healthy fetal tissues is not compatible with fundamental concepts of immunology, clinical microbiology and the derivation of germ-free mammals. These conclusions are important to our understanding of human immune development and illustrate common pitfalls in the microbial analyses of many other low-biomass environments. The pursuit of a fetal microbiome serves as a cautionary example of the challenges of sequence-based microbiome studies when biomass is low or absent, and emphasizes the need for a trans-disciplinary approach that goes beyond contamination controls by also incorporating biological, ecological and mechanistic concepts.
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- Tolmacheva, T., et al.
(author)
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The Hunneberg Stage (Ordovician) in the area east of S. Petersburg, north-western Russia
- 2001
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In: Paläontologische Zeitschrift. ; 74:4, s. 543-561
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Journal article (peer-reviewed)abstract
- The bio- and lithostratigraphy of the poorly knownearly Ordovician (Arenig) Hunneberg Stage is described fromthe area east of St. Petersburg (Putilovo Quarry and Lava river),where the Lakity Beds (Leetse Fm.) consist of glauconiticsands and silty clays. The described fauna includes graptolites,conodonts, brachiopods, acritarchs, foraminifers, and severalproblematic groups. The Lakity Beds are unique within thelower Ordovician sequence of the East Baltic in the abundanceof graptolites, co-occurring with conodonts. The conodontsfrom the lower part of the Lakity Beds belong to the uppermostsubzone (Oelandodus elongatus - Acodus deltatus deltatus) ofthe Paroistodus proteus Zone, coinciding with the lower partof the Tetragraptus phyllograptoides Zone. This suggests thatthere is a hiatus between the Lakity Beds and the underlyingNazya Formation. The lower Lakity Beds also contain thebrachiopods Leptembolon lingulaeformis and Eosiphonotretacf. acrotretomorpha, which suggest that they may be correlatedwith the Joa Member of the Leetse Formation in NorthEstonia. In the upper part of the Lakity Beds, conodonts of thePrioniodus elegans Zone co-occur with graptolites indicatingthe upper subzone of the Tetragraptus phyllograptoides Zonein the Scandinavian sections. There are still problems of definingand correlating the base of the Billingen Regional Stage,which are outside the scope of this paper.
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