PORTFOLIO

Contamination with toxic compounds such as arsenic and mercury is widespread, and continues to pose severe public and environmental health problems. The pollution originates both from natural processes, such as dissolution of minerals in aquifers, and from human activities, including mining and waste discharges. As a consequence, millions of people are at risk of developing chronic disease because they live in polluted areas and consume contaminated drinking water or food. Chronic toxicity can be limited and even reversed by avoiding contaminated material and changing to non-contaminated sources. However, many contaminated areas are also the most rural and underdeveloped, with little or no access to analytical facilities that can measure the extent of contamination. There is thus a clear need for simple yet accurate analytical tools that can determine what is safe for consumption. The tools have to be applicable in the field, on a variety of sample types (e.g., water, food stuffs), and ideally would even be useful to assess levels of individual exposure (e.g., via urine or blood samples).

In extension with previous and ongoing research in our laboratory, we propose that such «simple analytical technology» can be based on assays with living harmless bacteria. Such bacteria, or «bioreporters,» as they are called, are engineered to produce a quantifiable signal (color, fluorescence, light, electricity) in response to a specific contaminant. Since the bacteria are easy to produce, bioreporter assays could potentially provide the inexpensive «analytics» needed in the field. To date, in only a few cases have bioreporter assays been used outside the laboratory environment, but the results were quite promising.

The major aims of this project proposal are therefore (i) to develop appropriate and robust bioreporter assay protocols in order to be able to measure arsenic and mercury content in contaminated materials, and (ii), to test whether bioreporter assays can be used to measure the level of individual exposure in urine or blood samples. Once successful protocols are established, further steps for market introduction of bioreporter technology could be pursued. The project thus provides a «link» between basic research and potential future marketable technology.

The special thing about this project is that it proposes to develop routine, robust, easy-to-use and cheap analytics to measure arsenic and mercury using living bacteria. The technology is called bioreporter technology.

In contrast to most analytical technology, which is based on physical-chemical principles embedded in high-end electronic instruments, bioreporter technology exploits the cellular defense mechanisms of bacteria or yeast to allow detection of contaminants. The «bioreporters» are living cells in which the natural cellular defense reaction is coupled to the quantitative production of fluorescence or other easily measurable signals. The bioreporter measurement consists of a simple assay in which cells are brought into contact with the sample, and the intensity of the (fluorescent) signal produced by the cells is a measure for the contaminant concentration to which the cells have been exposed. Bioreporter assays can potentially form a good analytical alternative for measuring specific toxicants, even in the hands of non-specialists.

This project will specifically focus on developing and testing robust assay protocols for both biotic and abiotic samples. We will use arsenic and mercury as case studies, given the global problems associated with those compounds and the measurement accuracy that can be achieved with bioreporter assays. Recent news stories on mercury discharges in the Rhone basin (VS) have illustrated that Switzerland is not protected from such contamination, therefore, bioreporter assays may even find their way in Switzerland and other European countries.

Two new bioreporters were developed, one for arsenic and the other for mercury. The bioreporters permit detection of As in form of arsenite or arsenate in water between 1 and 100 µg/L, and Hg2+ between 0.1 and 100 µg/L. Different variants were produced which either emit fluorescence, bioluminescence or amperometric signal upon contact with the toxicant.

The bioassay was further optimized for use in human urine. The arsenic bioreporter could successfully detect between 1 and 6 µg As/L in urine. Urine samples of intoxicated patients were analyzed. A microfluidic test is under development to use bioreporter cells as a column to capture the toxicant and lower the detection limit.

The project has collaborated with the FP7 project BRAAVOO, which focuses on making biosensors for marine pollution, and the FNS NanoTera supported project Envirobot, to try and integrate bioreporters into aquatic robots. The project has participated in the organization of an international biosensor workshop, to be held in Lausanne from January 31 to Feb 6 2016, and a SCNAT-sponsored summer school in July 2016, on synthetic biology for beginners.

Berset, Y., Merulla, D., Joublin, A., Hatzimanikatis, V. & van der Meer, J. R. (2017) Mechanistic modeling of genetic circuits for ArsR arsenic regulation. ACS Synth Biol. accepted for publication;
Buffi, N., Beggah, S., Truffer, F., Geiser, M., van Lintel, H., Renaud, P., & van der Meer, J. R. (2016) An automated microreactor for semi-continuous biosensor measurements. Lab Chip 16: 1383-1392;
Merulla, D. & van der Meer, J. R. (2015) Regulatable and modulable background expression control in prokaryotic synthetic circuits by auxiliary repressor binding sites. ACS Synth Biol. DOI: 10.1021/acssynbio.5b00111;
Merulla D, Hatzimanikatis V, van der Meer JR. (2013).Tunable reporter signal production in feedback-uncoupled arsenic bioreporters. Microb Biotechnol DOI: 10.1111/1751-7915.12031;
Merulla, D., Buffi, N., Beggah, S., Truffer, F., Geiser, M., Renaud, P. and J. R. van der Meer. (2013) Bioreporters and biosensors for arsenic detection. Biotechnological solutions for a world-wide pollution problem. Curr. Opin. Biotechnol. 24(3):534-541;
Siegfried K, Endes C, Bhuiyan AF, Kuppardt A, Mattusch J, van der Meer JR, Chatzinotas A, Harms H. (2012) Field testing of arsenic in groundwater samples of bangladesh using a test kit based on lyophilized bioreporter bacteria. Environ Sci Technol 46: 3281-3287;
Buffi, N., Merulla, D., Beutier, J. Barbaud, F., Beggah, S., van Lintel, H., Renaud, P. and J. R. van der Meer. (2011) Development of a microfluidics biosensor for agarose-bead immobilized Escherichia coli bioreporter cells for arsenite detection in aqueous samples. Lab Chip 11: 2369-2377;
van der Meer JR, Belkin S. (2010) Where microbiology meets microengineering: design and applications of reporter bacteria. Nat Rev Microbiol 8: 511-522;
Lewis C, Beggah S, Pook C, Guitart C, Redshaw C, van der Meer JR, Readman JW, Galloway T. (2009) Novel use of a whole cell E. coli bioreporter as a urinary exposure biomarker. Environ Sci Technol. 43:423-428;
Trang PT, Berg M, Viet PH, Van Mui N, van der Meer JR. (2005) Bacterial bioassay for rapid and accurate analysis of arsenic in highly variable groundwater samples. Environ Sci Technol 39:7625-7630;
Wells M, Gösch M, Rigler R, Harms H, Lasser T, van der Meer JR. (2005) Ultrasensitive reporter protein detection in genetically engineered bacteria. Anal Chem. 77:2683-2689.

Bakterien helfen Ölspuren im Meer zu identizieren, Basler Zeitung, 24.3.2009
Erwin Schrödinger-Preis 2010 für die Entwicklung eines Arsendetektors
New Portable Kit Detects Arsenic In Wells, c&en, February 4, 2012