| 21. |
- Fulde, M., et al.
(författare)
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Neonatal selection by Toll-like receptor 5 influences long-term gut microbiota composition
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 560:7719
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Tidskriftsartikel (refereegranskat)abstract
- Alterations in enteric microbiota are associated with several highly prevalent immune-mediated and metabolic diseases(1-3), and experiments involving faecal transplants have indicated that such alterations have a causal role in at least some such conditions(4-6). The postnatal period is particularly critical for the development of microbiota composition, host-microbe interactions and immune homeostasis(7-9). However, the underlying molecular mechanisms of this neonatal priming period have not been defined. Here we report the identification of a host-mediated regulatory circuit of bacterial colonization that acts solely during the early neonatal period but influences life-long microbiota composition. We demonstrate age-dependent expression of the flagellin receptor Toll-like receptor 5 (TLR5) in the gut epithelium of neonate mice. Using competitive colonization experiments, we demonstrate that epithelial TLR5-mediated REG3 gamma production is critical for the counter-selection of colonizing flagellated bacteria. Comparative microbiota transfer experiments in neonate and adult wild-type and Tlr5-deficient germ-free mice reveal that neonatal TLR5 expression strongly influences the composition of the microbiota throughout life. Thus, the beneficial microbiota in the adult host is shaped during early infancy. This might explain why environmental factors that disturb the establishment of the microbiota during early life can affect immune homeostasis and health in adulthood.
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| 22. |
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| 23. |
- Hansen, Karin
(författare)
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Environment and host as large-scale controls of ectomycorrhizal fungi
- 2018
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Ingår i: NATURE. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687.
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Tidskriftsartikel (refereegranskat)abstract
- Explaining the large-scale diversity of soil organisms that drive biogeochemical processes — and their responses to environmental change - is critical. However, identifying consistent drivers of belowground diversity and abundance for some soil organisms at large spatial scales remains problematic. Here we investigate a major guild, the ectomycorrhizal fungi, across European forests at a spatial scale and resolution that is -to our knowledge -unprecedented, to explore key biotic and abiotic predictors of ectomycorrhizal diversity and to identify dominant responses and thresholds for change across complex environmental gradients. We show the effect of 38 host, environment, climate and geographical variables on ectomycorrhizal diversity, and define thresholds of community change for key variables. We quantify host specificity and reveal plasticity in functional traits involved in soil foraging across gradients. We conclude that environmental and host factors explain most of the variation in ectomycorrhizal diversity, that the environmental thresholds used as major ecosystem assessment tools need adjustment and that the importance of belowground specificity and plasticity has previously been underappreciated.
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| 24. |
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| 25. |
- Hashimoto, Takuya, et al.
(författare)
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The onset of star formation 250 million years after the Big Bang
- 2018
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 557:7705, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang(1-3). The abundance of star-forming galaxies is known to decline(4,5) from redshifts of about 6 to 10, but a key question is the extent of star formation at even earlier times, corresponding to the period when the first galaxies might have emerged. Here we report spectroscopic observations of MACS1149-JD1(6), a gravitationally lensed galaxy observed when the Universe was less than four per cent of its present age. We detect an emission line of doubly ionized oxygen at a redshift of 9.1096 +/- 0.0006, with an uncertainty of one standard deviation. This precisely determined redshift indicates that the red rest-frame optical colour arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15. Our results indicate that it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes.
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| 26. |
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| 27. |
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| 28. |
- Kardol, Paul, et al.
(författare)
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Long-term effects of species loss on community properties across contrasting ecosystems
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 557, s. 710-713
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Tidskriftsartikel (refereegranskat)abstract
- Biodiversity loss can heavily affect the functioning of ecosystems, and improving our understanding of how ecosystems respond to biodiversity decline is one of the main challenges in ecology(1-4). Several important aspects of the longer-term effects of biodiversity loss on ecosystems remain unresolved, including how these effects depend on environmental context(5-7). Here we analyse data from an across-ecosystem biodiversity manipulation experiment that, to our knowledge, represents the world's longest-running experiment of this type. This experiment has been set up on 30 lake islands in Sweden that vary considerably in productivity and soil fertility owing to differences in fire history(8,9). We tested the effects of environmental context on how plant species loss affected two fundamental community attributes-plant community biomass and temporal variability-over 20 years. In contrast to findings from artificially assembled communities(10-12), we found that the effects of species loss on community biomass decreased over time; this decrease was strongest on the least productive and least fertile islands. Species loss generally also increased temporal variability, and these effects were greatest on the most productive and most fertile islands. Our findings highlight that the ecosystem-level consequences of biodiversity loss are not constant across ecosystems and that understanding and forecasting these consequences necessitates taking into account the overarching role of environmental context.
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| 29. |
- Kelber, Almut
(författare)
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Birds perceive colours in categories
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 560, s. 311-312
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Humans perceive colours in categories such as red, even though we can discernred hues including ruby and crimson. It emerges that birds also categorizecolours and this affects their colour-discrimination ability.
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| 30. |
- Kern, Jan, et al.
(författare)
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Structures of the intermediates of Kok’s photosynthetic water oxidation clock
- 2018
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 563, s. 421-425
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Tidskriftsartikel (refereegranskat)abstract
- Inspired by the period-four oscillation in flash-induced oxygen evolution of photosystem II discovered by Joliot in 1969, Kok performed additional experiments and proposed a five-state kinetic model for photosynthetic oxygen evolution, known as Kok’s S-state clock or cycle1,2. The model comprises four (meta)stable intermediates (S0, S1, S2 and S3) and one transient S4 state, which precedes dioxygen formation occurring in a concerted reaction from two water-derived oxygens bound at an oxo-bridged tetra manganese calcium (Mn4CaO5) cluster in the oxygen-evolving complex3–7. This reaction is coupled to the two-step reduction and protonation of the mobile plastoquinone QB at the acceptor side of PSII. Here, using serial femtosecond X-ray crystallography and simultaneous X-ray emission spectroscopy with multi-flash visible laser excitation at room temperature, we visualize all (meta)stable states of Kok’s cycle as high-resolution structures (2.04–2.08 Å). In addition, we report structures of two transient states at 150 and 400 µs, revealing notable structural changes including the binding of one additional ‘water’, Ox, during the S2→S3 state transition. Our results suggest that one water ligand to calcium (W3) is directly involved in substrate delivery. The binding of the additional oxygen Ox in the S3 state between Ca and Mn1 supports O–O bond formation mechanisms involving O5 as one substrate, where Ox is either the other substrate oxygen or is perfectly positioned to refill the O5 position during O2 release. Thus, our results exclude peroxo-bond formation in the S3 state, and the nucleophilic attack of W3 onto W2 is unlikely.
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