426 research outputs found

    Diatom-inferred salinity records from the Arctic Siverian margin: Implications for fluvial runoff patterns during the Holocene

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    Diatom assemblages were employed to study temporal changes of Siberian river runoff on the Laptev Sea shelf. Using a correlation between freshwater diatoms (%) in core-top sediments and summer surface water salinities from the inner Kara Sea, salinity conditions were reconstructed for a site northeast of the Lena River Delta (present water depth 32 m) since 9 calendar years (cal) ka. The reconstruction indicate a strong, near-coastal, and river-influenced environment at the site until about 8.6 cal ka. Corroborated by comparison with other proxy records from further to the east, surface salinities increased from 9 to 14 until about 7.4 cal ka, owing to ongoing global sea level rise and synchronous southward shift of the coastline. Although riverine water became less influential at the site since then, salinities still varied between 12.5 and 15, particularly during the last 3.5 kyr. These more recent salinity fluctuations agree well with reconstructions from just north of the Lena Delta, emphasizing the strong linkage between shelf hydrography and riverine discharge patterns in Arctic Siberia

    Human Intestinal Cells Modulate Conjugational Transfer of Multidrug Resistance Plasmids between Clinical Escherichia coli Isolates.

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    Bacterial conjugation in the human gut microbiota is believed to play a major role in the dissemination of antibiotic resistance genes and virulence plasmids. However, the modulation of bacterial conjugation by the human host remains poorly understood and there is a need for controlled systems to study this process. We established an in vitro co-culture system to study the interaction between human intestinal cells and bacteria. We show that the conjugation efficiency of a plasmid encoding an extended spectrum beta-lactamase is reduced when clinical isolates of Escherichia coli are co-cultured with human intestinal cells. We show that filtered media from co-cultures contain a factor that reduces conjugation efficiency. Protease treatment of the filtered media eliminates this inhibition of conjugation. This data suggests that a peptide or protein based factor is secreted on the apical side of the intestinal cells exposed to bacteria leading to a two-fold reduction in conjugation efficiency. These results show that human gut epithelial cells can modulate bacterial conjugation and may have relevance to gene exchange in the gut

    Communication in bacteria: an ecological and evolutionary perspective

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    Individual bacteria can alter their behaviour through chemical interactions between organisms in microbial communities - this is generally referred to as quorum sensing. Frequently, these interactions are interpreted in terms of communication to mediate coordinated, multicellular behaviour. We show that the nature of interactions through quorum-sensing chemicals does not simply involve cooperative signals, but entails other interactions such as cues and chemical manipulations. These signals might have a role in conflicts within and between species. The nature of the chemical interaction is important to take into account when studying why and how bacteria react to the chemical substances that are produced by other bacteria

    Designing a Resilient Waterscape Using a Living Lab and catalyzing Polycentric Governance

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    The both polycentric governance and Living Labs concepts are based on decentralized participatory planning, co-design, and decisionmaking. While the concept of Living Lab is still emerging, the Isar-Plan (2000 ~ 2011) pioneered the approach for selecting, co-designing, and implementing nature-based solutions along the Isar River in Munich, Germany. Despite multiple governing authorities involved in the decisionmaking process of the Isar-Plan, the polycentric governance that led to the success of the project has to date not been analyzed. This paper presents the results of an ex-post-analysis of the Isar-Plan restoration planning process based on stakeholder interviews and a literature review. The contribution describes the evolution of Isar-Plan governance arrangements and discusses the Living Lab approaches to cooperative governance. The analysis demonstrates how polycentricity facilitated trust, learning, and the co-design of a resilient waterscape. The paper concludes that Living Labs can be a way of applying polycentric governance when autonomous and multi-scale decision-makers are collaboratively involved in the design of policy solutions, and vice-versa
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