Team:Bolivia/Description
Year after year the rural communities in Bolivia suffer from water shortages so they are pushed to look for other water resources in other places that sometimes are costly. In Bolivia, besides the natural environmental contamination with heavy metals, the mineral mining industry contributes to a rampant contamination of rivers and lakes , exceeding the concentration of heavy metals maximum permissible limits. The problem we face is that there is no cheap way of detecting them in water bodies: drinking water, lakes and rivers in the highlands of Bolivia. Arsenic is present in the 5 continents of the planet and affects about 15 million people in the world, being the most harmful metal, arsenic was reported to be found mainly in rural areas and cities of Bolivia representing a great threat, and its exposure can cause chronic diseases in major organs of the body. [1]
Background
Heavy metals have an atomic density of approximately 4000 kg/m3 or more. Being highly toxic (classified as such by international organizations), they cause serious illnesses in humans and in extreme cases even cancer, even if found in very low concentrations. Arsenic is found in all types of water of the Altiplano plateau, mostly in its oxidized form (As [V]) when released from its natural sources. It also precipitates in secondary minerals where it is generally stable in the form of saline precipitates and Fe oxides. [2]
Drinking water sources, used by mostly rural and indigenous communities around lakes and/or rivers in the Bolivian altiplano, are affected by drought and a combination of natural contaminants such as mineral deposits, brines, thermal waters and volcanic rocks, as well as anthropogenic sources related to mining activities and the release of acid mine drainage (AMD). [4]
In view of such problems, there is a need to constantly monitor arsenic concentrations in drinking water in order to take action, and for this reason it's important to understand heavy metal detection methods with emphasis on the design of cost-effective, environmentally friendly and user-acceptable sensor systems for on-site applications, in addition to high sensitivity, selectivity, reproducibility and stability.[5]
Nowadays, heavy metal detection can be achieved by spectrometric (high sensitivity, high cost), electrochemical (easy to use, limited sensitivity) and optical (easy to use, low selectivity) methods, i.e. sophisticated conventional techniques such as atomic absorption spectrometry and mass spectrometry, among others, involving the coupling of separation techniques, such as HPLC. These techniques are characterized by their high sensitivity, but have the disadvantages of long analysis time and high cost.[6]
In recent times, biotechnology and synthetic biology have been applied to the development of cell-free and whole-cell biosensors, which represent an alternative to traditional analytical methods, with comparable sensitivity, easy handling, portability, fast response and even cheaper cost, although sensitive to changes in temperature and pH.[7]
Our project
The project presented by our team is the design and construction of a bacterial biosensor to detect and quantify arsenic in drinking water sources. We also designed a portable device that greatly facilitate the handling of the biosensor, will allow the analysis of several samples at the same time and also will operate in areas outside the lab. In this way we propose an innovative and accessible alternative that contributes to an environmental monitoring service.
The detection principle of our biosensor will be the color generation through the production of a violet chromoprotein that will serve as a visible to the naked eye reporter. It can be arranged in traffic light patterns to offer semi-quantitative determinations or its color intensity be determined by a spectrophotometer to offer more detailed quantitative information.
Genetic constructs for arsenic detection
We engineered 4 constructs with a wide range of arsenic sensitivities and a visible to the naked eye output. To make this possible the design relies on 3 strategies: Intracellular ArsR density control, transcriptional amplifiers and a violet chromoprotein reporter.
As0 Construct: the most sensitive of all (>0.5 ppb), has a weak constitutive promoter for arsR expression and a double amplifier cascade (HrpRS-RinA).
As2 Construct: medium sensibility (>3 ppb), also has a weak constitutive promoter for arsR expression and a simple amplifier element (HrpRS).
As4 Construct: medium sensibility (>10 ppb), has a medium strength constitutive promoter for arsR expression, a transcriptional amplifier is not present.
As5 Construct: the least sensitive of all (>50 ppb), has a very strong constitutive promoter for arsR expression, a transcriptional amplifier is not present.
Arsenic detection using the FADSR device
FADSR (fast arsenic data sample reader) is the mechatronic portable device designed by the team. Is constructed of a resistant and lightweight material, suitable for field work but also will work well in the lab. Allows a fast interpretation, recording and sharing of results for the detection of arsenic in water samples. A color sensor will detect the violet reporter presence on paper strips and the data will be presented to the operator in real time, the device is capable to process quickly and accurately up to 18 different samples. For field operation especially, the device contains batteries that allow it to operate normally without the need for a continuous power supply. The design was strongly inspired by iGEM Peshawar's 2017 MAX (Metal Alert Xystem).[8]
References
[1]. De Loma J, Tirado N, Ascui F, Levi M, Vahter M, Broberg K, et al. Elevated arsenic exposure and efficient arsenic metabolism in indigenous women around Lake Poopó, Bolivia. Science of The Total Environment. marzo de 2019;657:179-86.
[2]. De Loma J, Tirado N, Ascui F, Levi M, Vahter M, Broberg K, et al. Elevated arsenic exposure and efficient arsenic metabolism in indigenous women around Lake Poopó, Bolivia. Science of The Total Environment. marzo de 2019;657:179-86.
[3]. Tapia J, Murray J, Ormachea M, Tirado N, Nordstrom DK. Origin, distribution, and geochemistry of arsenic in the Altiplano-Puna plateau of Argentina, Bolivia, Chile, and Perú. Science of The Total Environment. agosto de 2019;678:309-25.
[4]. Ormachea Muñoz, Mauricio, & Quintanilla Aguirre, Jorge. (2014). DISTRIBUTION OF GEOGENIC ARSENIC IN SUPERFICIAL AND UNDERGROUND WATER IN CENTRAL BOLIVIAN HIGHLANDS. Revista Boliviana de Química, 31(2), 54-60. Recuperado en 15 de septiembre de 2021, de
[5] Quaghebeur W, Mulhern RE, Ronsse S, Heylen S, Blommaert H, Potemans S, et al. Arsenic contamination in rainwater harvesting tanks around Lake Poopó in Oruro, Bolivia: An unrecognized health risk. Science of The Total Environment. octubre de 2019;688:224-30.
[6] Usman K, Al-Ghouti MA, Abu-Dieyeh MH. Phytoremediation: Halophytes as Promising Heavy Metal Hyperaccumulators. En: Saleh HE-DM, Aglan RF, editores. Heavy Metals [Internet]. InTech; 2018 [citado 15 de septiembre de 2021].
[7] Rajakovic, L., & Rajakovic-Ognjanovic, V. (2018). Arsenic in Water: Determination and Removal. En M. Stoytcheva & R. Zlatev (Eds.), Arsenic—Analytical and Toxicological Studies. InTech.
[8] Devi, P., Thakur, A., Lai, RY, Saini, S., Jain, R. y Kumar, P. (2019). Avances en los materiales para la detección óptica de arsénico en agua. Tendencias de TrAC en química analítica , 110 , 97-115.