| 1. |
- Pelve, Erik A., 1980-, et al.
(författare)
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Cdv-based cell division and cell cycle organization in the thaumarchaeon Nitrosopumilus maritimus
- 2011
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 82:3, s. 555-566
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Tidskriftsartikel (refereegranskat)abstract
- Cell division is mediated by different mechanisms in different evolutionary lineages. While bacteria and euryarchaea utilize an FtsZ-based mechanism, most crenarchaea divide using the Cdv system, related to the eukaryotic ESCRT-III machinery. Intriguingly, thaumarchaeal genomes encode both FtsZ and Cdv protein homologues, raising the question of their division mode. Here, we provide evidence indicating that Cdv is the primary division system in the thaumarchaeon Nitrosopumilus maritimus. We also show that the cell cycle is differently organized as compared to hyperthermophilic crenarchaea, with a longer pre-replication phase and a shorter post-replication stage. In particular, the time required for chromosome replication is remarkably extensive, 15-18 h, indicating a low replication rate. Further, replication did not continue to termination in a significant fraction of N. maritimus cell populations following substrate depletion. Both the low replication speed and the propensity for replication arrest are likely to represent adaptations to extremely oligotrophic environments. The results demonstrate that thaumarchaea, crenarchaea and euryarchaea display differences not only regarding phylogenetic affiliations and gene content, but also in fundamental cellular and physiological characteristics. The findings also have implications for evolutionary issues concerning the last archaeal common ancestor and the relationship between archaea and eukaryotes.
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| 2. |
- Pelve, Erik A., et al.
(författare)
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Mapping of active replication origins in vivo in thaum- and euryarchaeal replicons
- 2013
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 90:3, s. 538-550
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Tidskriftsartikel (refereegranskat)abstract
- We report mapping of active replication origins in thaum- and euryarchaeal replicons using high-throughput sequencing-based marker frequency analysis. The chromosome of the thaumarchaeon Nitrosopumilus maritimus is shown to contain a single origin of replication, whereas the main chromosome in the halophilic euryarchaea Haloferax mediterranei and Haloferax volcanii each contains two origins. All replication origins specified bidirectional replication, and the two origins in the halophiles were initiated in synchrony. The pHM500 plasmid of H.mediterranei is shown to contain a single origin, and the copy numbers of five plasmid replicons in the two halophiles were inferred to be close to that of the main chromosome. Origin recognition boxes (ORBs) that provide binding sites for Orc1/Cdc6 replication initiator proteins are identified at all chromosomal origins, as well as in a range of additional thaumarchaeal species. An annotation update is provided for all three species.
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| 3. |
- Andersson, Anders, et al.
(författare)
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Replication-biased genome organisation in the crenarchaeon Sulfolobus
- 2010
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 11, s. 454-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Species of the crenarchaeon Sulfolobus harbour three replication origins in their single circular chromosome that are synchronously initiated during replication. Results: We demonstrate that global gene expression in two Sulfolobus species is highly biased, such that early replicating genome regions are more highly expressed at all three origins. The bias by far exceeds what would be anticipated by gene dosage effects alone. In addition, early replicating regions are denser in archaeal core genes (enriched in essential functions), display lower intergenic distances, and are devoid of mobile genetic elements. Conclusion: The strong replication-biased structuring of the Sulfolobus chromosome implies that the multiple replication origins serve purposes other than simply shortening the time required for replication. The higher-level chromosomal organisation could be of importance for minimizing the impact of DNA damage, and may also be linked to transcriptional regulation.
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| 4. |
- Ettema, Thijs J. G., et al.
(författare)
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Rolf Bernander (1956-2014) : pioneer of the archaeal cell cycle Obituary
- 2014
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 92:5, s. 903-909
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- On 19 January 2014 Rolf (Roffe') Bernander passed away unexpectedly. Rolf was a dedicated scientist; his research aimed at unravelling the cell biology of the archaeal domain of life, especially cell cycle-related questions, but he also made important contributions in other areas of microbiology. Rolf had a professor position in the Molecular Evolution programme at Uppsala University, Sweden for about 8 years, and in January 2013 he became chair professor at the Department of Molecular Biosciences, The Wenner-Gren Institute at Stockholm University in Sweden. Rolf was an exceptional colleague and will be deeply missed by his family and friends, and the colleagues and co-workers that he leaves behind in the scientific community. He will be remembered for his endless enthusiasm for science, his analytical mind, and his quirky sense of humour.
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| 5. |
- Iversen, Kia Noehr, 1987, et al.
(författare)
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The Effects of High Fiber Rye, Compared to Refined Wheat, on Gut Microbiota Composition, Plasma Short Chain Fatty Acids, and Implications for Weight Loss and Metabolic Risk Factors (the RyeWeight Study)
- 2022
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Ingår i: Nutrients. - : MDPI AG. - 2072-6643 .- 2072-6643. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Consumption of whole grain and cereal fiber have been inversely associated with body weight and obesity measures in observational studies but data from large, long-term randomized interventions are scarce. Among the cereals, rye has the highest fiber content and high rye consumption has been linked to increased production of gut fermentation products, as well as reduced risks of obesity and metabolic disease. The effects on body weight and metabolic risk factors may partly be mediated through gut microbiota and/or their fermentation products. We used data from a randomized controlled weight loss trial where participants were randomized to a hypocaloric diet rich in either high fiber rye foods or refined wheat foods for 12 weeks to investigate the effects of the intervention on gut microbiota composition and plasma short chain fatty acids, as well as the potential association with weight loss and metabolic risk markers. Rye, compared to wheat, induced some changes in gut microbiota composition, including increased abundance of the butyrate producing Agathobacter and reduced abundance of [Ruminococcus] torques group, which may be related to reductions in low grade inflammation caused by the intervention. Plasma butyrate increased in the rye group. In conclusion, intervention with high fiber rye foods induced some changes in gut microbiota composition and plasma short chain fatty acid concentration, which were associated with improvements in metabolic risk markers as a result of the intervention.
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| 6. |
- Nordin, Elise, 1985, et al.
(författare)
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Effects of FODMAPs and Gluten on Gut Microbiota and Their Association with the Metabolome in Irritable Bowel Syndrome: A Double-Blind, Randomized, Cross-Over Intervention Study
- 2023
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Ingår i: Nutrients. - : MDPI AG. - 2072-6643 .- 2072-6643. ; 15:13
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Tidskriftsartikel (refereegranskat)abstract
- Background: A mechanistic understanding of the effects of dietary treatment in irritable bowel syndrome (IBS) is lacking. Our aim was therefore to investigate how fermentable oligo- di-, monosaccharides, and polyols (FODMAPs) and gluten affected gut microbiota and circulating metabolite profiles, as well as to investigate potential links between gut microbiota, metabolites, and IBS symptoms. Methods: We used data from a double-blind, randomized, crossover study with week-long provocations of FODMAPs, gluten, and placebo in participants with IBS. To study the effects of the provocations on fecal microbiota, fecal and plasma short-chain fatty acids, the untargeted plasma metabolome, and IBS symptoms, we used Random Forest, linear mixed model and Spearman correlation analysis. Results: FODMAPs increased fecal saccharolytic bacteria, plasma phenolic-derived metabolites, 3-indolepropionate, and decreased isobutyrate and bile acids. Gluten decreased fecal isovalerate and altered carnitine derivatives, CoA, and fatty acids in plasma. For FODMAPs, modest correlations were observed between microbiota and phenolic-derived metabolites and 3-indolepropionate, previously associated with improved metabolic health, and reduced inflammation. Correlations between molecular data and IBS symptoms were weak. Conclusions: FODMAPs, but not gluten, altered microbiota composition and correlated with phenolic-derived metabolites and 3-indolepropionate, with only weak associations with IBS symptoms. Thus, the minor effect of FODMAPs on IBS symptoms must be weighed against the effect on microbiota and metabolites related to positive health factors.
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| 7. |
- Pelve, Erik A., 1980-, et al.
(författare)
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Bacterial Succession on Sinking Particles in the Ocean's Interior
- 2017
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Sinking particles formed in the photic zone and moving vertically through the water column are a main mechanism for nutrient transport to the deep ocean, and a key component of the biological carbon pump. The particles appear to be processed by a microbial community substantially different from the surrounding waters. Single cell genomics and metagenomics were employed to describe the succession of dominant bacterial groups during particle processing. Sinking particles were extracted from sediment traps at Station Aloha in the North Pacific Subtropical Gyre (NPSG) during two different trap deployments conducted in July and August 2012. The microbial communities in poisoned vs. live sediment traps differed significantly from one another, consistent with prior observations by Fontanez et al. (2015). Partial genomes from these communities were sequenced from cells belonging to the genus Arcobacter (commensalists potentially associated with protists such as Radiolaria), and Vibrio carnpbellii (a group previously reported to be associated with crustacea). These bacteria were found in the particle-associated communities at specific depths in both trap deployments, presumably due to their specific host-associations. Partial genomes were also sequenced from cells belonging to Idiomarina and Kangiella that were enriched in live traps over a broad depth range, that represented a motile copiotroph and a putatively non-motile algicidal saprophyte, respectively. Planktonic bacterial cells most likely caught in the wake of the particles belonging to Actinomarina and the SAR11 Glade were also sequenced. Our results suggest that similar groups of eukaryote-associated bacteria are consistently found on sinking particles at different times, and that particle remineralization involves specific, reproducible bacterial succession events in oligotrophic ocean waters.
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| 8. |
- Pelve, Erik A., et al.
(författare)
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Four chromosome replication origins in the archaeon Pyrobaculum calidifontis
- 2012
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 85:5, s. 986-995
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Tidskriftsartikel (refereegranskat)abstract
- Replication origins were mapped in hyperthermophilic crenarchaea, using high-throughput sequencing-based marker frequency analysis. We confirm previous origin mapping in Sulfolobus acidocaldarius, and demonstrate that the single chromosome of Pyrobaculum calidifontis contains four replication origins, the highest number detected in a prokaryotic organism. The relative positions of the origins in both organisms coincided with regions enriched in highly conserved (core) archaeal genes. We show that core gene distribution provides a useful tool for origin identification in archaea, and predict multiple replication origins in a range of species. One of the P. calidifontis origins was mapped in detail, and electrophoretic mobility shift assays demonstrated binding of the Cdc6/Orc1 replication initiator protein to a repeated sequence element, denoted Orb-1, within the origin. The high-throughput sequencing approach also allowed for an annotation update of both genomes, resulting in the restoration of open reading frames encoding proteins involved in, e.g., sugar, nitrate and energy metabolism, as well as in glycosylation and DNA repair.
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| 9. |
- Pelve, Erik A., 1980-
(författare)
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Unique Solutions to Universal Problems : Studies of the Archaeal Cell
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Archaea is one of the three domains of life and studies of archaeal biology are important for understanding of life in extreme environments, fundamental biogeochemical processes, the origin of life, the eukaryotic cell and their own, unique biology. This thesis presents four studies of the archaeal cell, using the extremophilic Sulfolobus and ocean living Nitrosopumilus as model systems. Cell division in crenarchaea is shown to be carried out by a previously unknown system named Cdv (cell division). The system shares homology with the eukaryotic ESCRT-III system which is used for membrane reorganization during vesicle formation, viral release and cytokinesis. Organisms of the phylum Thaumarchaeota also use the Cdv system, despite also carrying genes for the euryarchaeal and bacterial cell division system FtsZ. The thaumarchaeal cell cycle is demonstrated to be dominated by the prereplicative and replicative stage, in contrasts to the crenarchaeal cell cycle where the cell at the majority of the time resides in the postreplicative stage. The replication rate is remarkably low and closer to what is measured for eukaryotes than other archaea. The gene organization of Sulfolobus is significantly associated with the three origins of replication. The surrounding regions are dense with genes of high importance for the organisms such as highly transcribed genes, genes with known function in fundamental cellular processes and conserved archaeal genes. The overall gene density is elevated and transposons are underrepresented. The archaeal virus SIRV2 displays a lytic life style where the host cell at the final stage of infection is disrupted for release of new virus particles. The remarkable pyramid-like structure VAP (virus associated pyramids), that is formed independently of the virus particle, is used for cell lysis. The research presented in this thesis describes unique features of the archaeal cell and influences our understanding of the entire tree of life.
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| 10. |
- Skantze, Viktor, 1992, et al.
(författare)
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Differential Responders to a Mixed Meal Tolerance Test Associated with Type 2 Diabetes Risk Factors and Gut Microbiota—Data from the MEDGI-Carb Randomized Controlled Trial
- 2023
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Ingår i: Nutrients. - : MDPI. - 2072-6643 .- 2072-6643. ; 15:20
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Tidskriftsartikel (refereegranskat)abstract
- The global prevalence of type 2 diabetes mellitus (T2DM) has surged in recent decades, and the identification of differential glycemic responders can aid tailored treatment for the prevention of prediabetes and T2DM. A mixed meal tolerance test (MMTT) based on regular foods offers the potential to uncover differential responders in dynamical postprandial events. We aimed to fit a simple mathematical model on dynamic postprandial glucose data from repeated MMTTs among participants with elevated T2DM risk to identify response clusters and investigate their association with T2DM risk factors and gut microbiota. Data were used from a 12-week multi-center dietary intervention trial involving high-risk T2DM adults, comparing high- versus low-glycemic index foods within a Mediterranean diet context (MEDGICarb). Model-based analysis of MMTTs from 155 participants (81 females and 74 males) revealed two distinct plasma glucose response clusters that were associated with baseline gut microbiota. Cluster A, inversely associated with HbA1c and waist circumference and directly with insulin sensitivity, exhibited a contrasting profile to cluster B. Findings imply that a standardized breakfast MMTT using regular foods could effectively distinguish non-diabetic individuals at varying risk levels for T2DM using a simple mechanistic model.
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