Soil microbial community structure and functionality changes in response to long-term metal and radionuclide pollution

Microbial communities are essential for a healthy soil ecosystem. Metals and radionuclides can exert a persistent pressure on the soil microbial community. However, little is known on the effect of long-term co-contamination of metals and radionuclides on the microbial community structure and functionality. We investigated the impact of historical discharges of the phosphate and nuclear industry on the microbial community in the Grote Nete river basin in Belgium. Eight locations were sampled along a transect to the river edge and one location further in the field. Chemical analysis demonstrated a metal and radionuclide contamination gradient and revealed a distinct clustering of the locations based on all metadata. Moreover, a relation between the chemical parameters and the bacterial community structure was demonstrated. Although no difference in biomass was observed between locations, cultivation-dependent experiments showed that communities from contaminated locations survived better on singular metals than communities from control locations. Furthermore, nitrification, a key soil ecosystem process seemed affected in contaminated locations when combining metadata with microbial profiling. These results indicate that long-term metal and radionuclide pollution impacts the microbial community structure and functionality and provides important fundamental insights into microbial community dynamics in co-metal-radionuclide contaminated sites

Effects of environmental parameters on Lemna minor growth: An integrated experimental and modelling approach

Pollution of surface waters is a worldwide problem for people and wildlife. Remediation and phytoremediation approaches can offer a solution to deal with specific scenarios. Lemna minor, commonly known as duckweed, can absorb and accumulate pollutants in its biomass. To evaluate if L. minor could be applied for phytoremediation purposes, it is necessary to further investigate its remediation capability and to identify which parameters affect the remediation process. Such a model must include both plant growth and pollutant exchange. A remediation model based on a robust experimental study can help to evaluate L. minor as a proper remediation strategy and to predict the outcome of a L. minor based remediation system. To set up this model, this paper focusses on a detailed experimental study and a comprehensive mathematical modelling approach to represent L. minor growth as a function of biomass, temperature, light irradiation and variable nutrient concentrations. The influence of environmental conditions on L. minor growth was studied, by composing 7 days growth curves. Plants were grown under predefined environmental conditions (25°C, 14h photoperiod, 220 μmol m−2 s−1 light intensity and a modified Hoagland solution with 23.94 mg N L−1 and 3.10 mg P L−1 (N:P ratio of 7.73)) as standard for all experiments. The influence of different temperatures (6, 10, 15, 20, 25, 30 and 35°C), light intensities (63, 118, 170, 220 and 262 μmol m−2 s−1), photoperiods (12h and 14h) and N:P ratios (1.18, 3.36, 7.73 and 29.57) were tested in the model. As a result, a growth model was optimised using separate datasets for temperature, light intensity, photoperiod and nutrients and validated by further integrated testing. The growth model is a stable platform for application in phytoremediation of radionuclides in contaminated water, to be extended in future studies with information of pollutant uptake, pollutant-nutrient interactions and transfer to the biomass

Rhizophagus irregularis MUCL 41833 can colonize and improve P uptake of Plantago lanceolata after exposure to ionizing gamma radiation in root organ culture

Long-lived radionuclides such as 90Sr and 137Cs can be naturally or accidentally deposited in the upper soil layers where they emit β/γ radiation. Previous studies have shown that arbuscular mycorrhizal fungi (AMF) can accumulate and transfer radionuclides from soil to plant, but there have been no studies on the direct impact of ionizing radiation on AMF. In this study, root organ cultures of the AMF Rhizophagus irregularis MUCL 41833 were exposed to 15.37, 30.35, and 113.03 Gy gamma radiation from a 137Cs source. Exposed spores were subsequently inoculated to Plantago lanceolata seedlings in pots, and root colonization and P uptake evaluated. P. lanceolata seedlings inoculated with non-irradiated AMF spores or with spores irradiated with up to 30.35 Gy gamma radiation had similar levels of root colonization. Spores irradiated with 113.03 Gy gamma radiation failed to colonize P. lanceolata roots. P content of plants inoculated with non-irradiated spores or of plants inoculated with spores irradiated with up to 30.35 Gy gamma radiation was higher than in non-mycorrhizal plants or plants inoculated with spores irradiated with 113.03 Gy gamma radiation. These results demonstrate that spores of R. irregularis MUCL 41833 are tolerant to chronic ionizing radiation at high doses

Computer-mediated communication in TEI: What lies ahead

The social web has brought forth various genres of interpersonal communication (computer-mediated communication, henceforth: cmc) such as chats, discussion forums, wiki talk pages, Twitter, comment and discussion threads on weblogs and social network sites. These genres display linguistic and structural peculiarities which differ both from speech and from written text. Projects that want to build and exchange cmc corpora would greatly benefit from a standard that allows the user to annotate these peculiarities in TEI. From the perspective of several corpus projects which aim at building and annotating cmc corpora for several European languages, this panel will discuss how the models provided by the TEI encoding framework may be adapted to the special requirements of cmc genres. The basis of the discussion is a customized TEI schema presented at the TEI conference held in Würzburg 2011 (Beißwenger et al. 2012)1. The panel papers will elaborate on basic features that a TEI standard for cmc resources should include and outline open issues with which further work will have to deal. The overall goal of the panel is to stimulate the discussion within the TEI community about how a standard for the representation of cmc in TEI should look like and what might be a practical and reasonable way to go about creating such a standard. In order to push the development of a general standard for the representation of cmc genres and cmc discourse forward, the papers in the panel will present problem overviews for basic issues in representing cmc features in TEI P5 and outline perspectives as well as first suggestions for the treament of these challenges through modifications and expansions of the encoding framework. Starting from these suggestions, the group is planning to work out feature requests and load them onto the TEI projects page on sourceforge.net