Heavy metal ion influence on the photosynthetic growth of Rhodobacter sphaeroides

The potential of purple non-sulphur bacteria for bioremediation was assessed by investigating the ability of Rhodobacter sphaeroides strain R26.1 to grow photosynthetically in heavy metal contaminated environments. Bacterial cultures were carried out in artificially polluted media, enriched with the transition metal ions Hg2+, Cu2+, Fe2+, Ni2+, Co2+, MoO4(2-), and CrO4(2-) in millimolar concentration range. For each investigated ion the effect on growth parameters was evaluated. The analysis of concentration-effect curves revealed a differentiated response, indicating that diverse mechanisms of tolerance and/or resistance are involved. Adaptation or selection procedures were not applied, leading to assess intrinsic abilities of coping with these contaminants. The microorganism proved to be highly tolerant to heavy metal exposure, especially towards Co2+, Fe2+ and MoO4(2-). In addition Ni2+ and Co2+ were found to decrease the cellular content of light harvesting complexes. A characteristic behavior was observed with mercuric ions, which produced a significant increase of the lag-phase.     

Arsenate tolerance in Silene paradoxa does not rely on phytochelatin-dependent sequestration

Arsenate tolerance, As accumulation and As-induced phytochelatin accumulation were compared in populations of Silene paradoxa, one from a mine site enriched in As, Cu and Zn, the other from an uncontaminated site. The mine population was significantly more arsenate-tolerant. Arsenate uptake and root-to-shoot transport were slightly but significantly higher in the non-mine plants. The difference in uptake was quantitatively insufficient to explain the difference in tolerance between the populations. As accumulation in the roots was similar in both populations, but the mine plants accumulated much less phytochelatins than the non-mine plants. The mean phytochelatin chain length, however, was higher in the mine population, possibly due to a constitutively lower cellular glutathione level. It is argued that the mine plants must possess an arsenic detoxification mechanism other than arsenate reduction and subsequent phytochelatin-based sequestration. This alternative mechanism might explain at least some part of the superior tolerance in the mine plants.     

Integrating methods for the environmental sustainability: the SPIn-Eco Project in the Province of Siena (Italy)

This paper shows how different methods can be integrated in order to provide an organic evaluation of the environmental sustainability at the territorial level. A territory is a complex, dynamic and open system where a population develops, uses resources, produces goods and services, consumes, depletes and finally obtains economic results. All these elements characterise human behaviour, which can be monitored, measured and compared to the capacity of the environment to sustain it in the long run. The SPIn-Eco Project for the Province of Siena (Italy) is described as an example of an environmental sustainability assessment of an area, and its methods (Ecological Footprint, Greenhouse Gas Inventory, Extended Exergy Analysis, Emergy Evaluation, Life Cycle Assessment (LCA) and Remote Sensing) are briefly introduced. This Project has been proposed and funded by the most important provincial administrative and financial institutions in the territory (the Administration of the Province of Siena and the Monte dei Paschi Foundation, respectively), and was designed and realised in 4 years (2001-2004) by a research team coordinated by the University of Siena.     

Use of sulfadimethoxine in intensive calf farming: evaluation of transfer to stable manure and soil

After prophylactic treatment of 50 calves with 62mgkg(-1)day(-1) of sulfadimethoxine (SDM) for five days, the levels of the drug over time were followed in feces, bedding and stable manure, and then in the soil of a manured field and surrounding drainage courses. Analysis were done by HPLC after applying to the different matrices a quick and simple extraction procedure. The half-life of the drug in bedding was very short (24h). In stable manure the degradation rate of the drug slowed down and the calculated half-life was 64 days, with 390microgkg(-1) of SDM still detectable after three months maturation. However, in a five months matured stable manure obtained from other groups of calves subjected to the same prophylactic treatment, levels of SDM were <50muicrokg(-1) (LOD of the analytical method). After field fertilization with this manure, no traces of SDM were found in soil (LOD 10microgkg(-1)) or in the water (LOD 2microgl(-1)) from the surrounding drainage courses. Using the internationally recognised DAPHTOXKIT-Ftrade mark, a SDM toxicity test toward Daphnia magna was performed in the range 10-100mgl(-1). The test gave negative results both after 24 and 48h, confirming that microcrustaceans are less sensitive than other models to the toxicity of antibacterials. However, based on data from other authors, concerning algal toxicity and microbial inhibition, and on the analytical results from the current field study, the calculated worst-case EC50/PEC ratio for SDM both in freshwater and in soil was still >1000.