Recently it has been proposed to use sensors based on genetically engineered reporter cells to perform continuous online water monitoring. Here we describe the design, assembly and performance of a novel flow-through device with immobilized genetically modified yeast cells that produce a fluorescent protein upon stimulation with diclofenac whose intensity is then detected by fluorescence microscopy. Although other devices employing immobilized cells for the detection of various analytes have already been described before, as novelty our system allows safe enclosure of the sensor cells, and thus, to obtain fluorescent signals that are not falsified by a loss of cells. Furthermore, the yeast cells are prevented from being released into the environment. Despite the safe containment, the immobilized reporter cells are accessible to nutrients and analytes. They thus have both the ability to grow and respond to the analyte. Both in cell culture medium and standardized synthetic wastewater, we are able to differentiate between diclofenac concentrations in a range from 10 to 100 μM. As particularly interesting feature, we show that only the biologically active fraction of diclofenac is detected. Nowadays, contamination of wastewater with diclofenac and other pharmaceutical residues is becoming a severe problem. Our investigations may pave the way for an easy-to-use and cost-efficient wastewater monitoring method.

During the obligate biotrophic interaction of Plasmodiophora brassicae with members of the Brassicaceae, the host roots show hypertrophy and galls are established. An increased auxin pool appears to correlate with cell expansion and cell division, but the origin of the free auxin is not yet clear. As previous results point to increased IAA-hydrolytic activity in infected roots of Brassica rapa at later time points of infection, we isolated IAA-amidohydrolase-like genes from various tissues. We cloned full-length cDNAs of two genes with high homology to the Arabidopsis IAR3 (Br-IAR3) as well as full-length clones corresponding to the Arabidopsis ILL2/ILL1 (Br-ILL2) and ILL6 (Br-ILL6) hydrolase genes. Using heterologous expression in Escherichia coli, we showed that Br-IAR3 24 and Br-ILL2 possess hydrolytic activity in vitro. Real-time reverse transcription (RT)-PCR revealed that only Br-IAR3 25 and Br-ILL6 are expressed differentially during clubroot disease, but showed a decreased expression at later time point of infection. These findings are discussed with regard to a negative regulation in IAA homeostasis during clubroot disease.