A simple mediatorless amperometric method using the cyanobacterium Synechococcus leopoliensis for the detection of phytotoxic pollutants.

The unicellular cyanobacterium Synechoccocus leopoliensis is used in a micro-electrochemical cell to generate photocurrents. The photocurrent is dependent on photosynthetic electron transport and is mediated by hydrogen peroxide formation following the reduction of oxygen on the acceptor side of photosystem I. This is the first known application of cyanobacteria in an electrochemical device where no artificial electroactive mediator is needed. The potential for the development of this micro-electrochemical cell for the detection of phytotoxic pollutants, such as herbicides and toxic metal cations, using the photosynthetic system of the cyanobacteria without interference from added electron acceptor is discussed.

Influence of current velocity on cadmium accumulation by an aquatic moss and the consequences for its use as a biomonitor.

Aquatic mosses are widely used as biomonitors of contaminant concentrations in running waters. The results of several previous studies suggest that metal concentrations in mosses are influenced by current velocity and that this variable should be taken into account when mosses are used as metal biomonitors. However, in these studies, the purported influence of water velocity was confounded by other uncontrolled variables. We conducted our study to test the influence of current velocity on Cd accumulation by the riverine moss Fontinalis dalecarlica. We found no difference in Cd accumulation over 2 weeks by moss exposed in the laboratory to a constant Cd concentration over a wide range of current velocities (0.01-0.70 m s-1) that occur in the field. Similarly, the results of a field experiment, in which we exposed F. dalecarlica in a Cd-contaminated creek to four current velocities (0.05-0.50 m s-1), confirmed that in nature Cd accumulation by this moss is not influenced by current velocity. We show that a bioaccumulation model that ignores current velocity describes Cd accumulation by F. dalecarlica very well. Our results suggest that current velocity does not have to be considered when using aquatic mosses as metal biomonitors.