mRNA expression of a cadmium-responsive gene is a sensitive biomarker of cadmium exposure in the soil collembolan Folsomia candida

The gene expression of environmental organisms is useful as a biomarker of environmental pollution. One of its advantages is high sensitivity. We identified the cDNA of a novel cadmium-responsive gene in the soil collembolan Folsomia candida. The deduced protein, designated “metallothionein-like motif containing protein” (MTC), was cysteine-rich and contained a metallothionein-like motif with similarity to metallothionein, but had a much longer sequence than metallothionein and contained repeated sequences of amino acids. Expression of MTC mRNA was sensitively induced by cadmium exposure at 0.3 mg/kg of dry food, a concentration at which toxic effects are not observed, but expression was not affected by γ-ray exposure (an inducer of oxidative stress). These findings suggest that MTC is involved in cadmium-binding processes rather than in oxidative-stress responses. In conclusion, we suggest that gene expression of MTC may be a candidate biomarker for detecting low levels of cadmium contamination in soil.     

Iron-induced decomposition of perfluorohexanesulfonate in sub- and supercritical water

Decomposition of perfluorohexanesulfonate (PFHS), a bioaccumulative analogue of perfluorooctanesulfonate (PFOS), in sub- and supercritical water was investigated. Although PFHS was only slightly reactive in pure subcritical water at 350 degrees C, it decomposed to F(-) and SO(4)(2-) ions when the temperature was increased to 380 degrees C, at which temperature the water became supercritical state. Addition of zerovalent iron to the reaction system dramatically accelerated PFHS decomposition to F(-) ions in both sub- and supercritical water: for example, when the initial PFHS concentration was 741microM, the F(-) yields at 350 degrees C were 4.13-16.0 times as high as those in the absence of iron, depending on the amount and the particle size of the iron powder. After the reactions, small amounts of CO(2) and CF(3)H were also detected in the gas phase; these increased with temperature, and the amount of CF(3)H increased markedly when the reaction was carried out in supercritical water. Increasing the specific surface area of the iron powder markedly increased PFHS consumption and F(-) formation in the aqueous phase, which indicates that the reactions occurred on the iron surface and that the increased specific surface area was a key factor in accelerating the decomposition of PFHS to F(-) ions.