Clean environment is essential for the survival of living organisms. The quality of the environmental factors affects health of living beings.  Automobile emissions release various harmful gases like Carbon monoxide (CO), Nitrous oxide (NOx) or toxic volatile chemicals like Xylene, Benzene and Toluene in the air leading to deterioration of the air quality. The alleviation of these hazardous air pollutants has been linked to various cardiovascular and respiratory diseases. On the other hand, excessive use of pesticides and insecticides contaminates both soil and water. Phenolic compounds are one of the common contaminants added to soil and water due to excessive use of pesticides and insecticides. These pollutants are measured using different techniques like Gas Chromatography – Flame Ionization Detector (GC-FID), Proton Transfer Reaction – Mass Spectrometry (PTR-MS) etc. which are very costly and cannot be installed at every place.  Due to limitation of these sophisticated techniques, alternative and cost effective approaches are required for the measuring and reducing the levels of pollutants. Therefore, to curb this problem, many groups have tried to engineer microorganisms to respond to levels of pollutants present in the environment. However, they were not very successful in their approaches as they had compromised on one of the two factors i.e. sensitivity and efficiency. 

We tried to approach this problem in more systematic manner by designing a synthetic circuit using positive feedback loops for rapid response and excitable dynamics while negative feedback loops for improved sensitivity, thus creating a robust, stable and sensitive system to detect, measure and capture major pollutants of air – NOx, acetaldehyde, xylene and CO and harmful chemicals - pesticides and insecticides. These synthetic circuits have been verified through chemical kinetics and simulations for their feasibility. These synthetic circuits when engineered in E. coli will show response by changing its color based on the levels of pollutants present in the environment. We have designed the circuit for all the above mentioned noxious substances. Currently, we are focusing to make a working model for the phenolic circuit system to measure phenolic compounds, and its success will show the feasibility and lucrativeness of other circuits. At the later part of the project, we will aim to introduce the engineered bacteria on paper in a ready to use format. These paper based sensors can cut down the cost involved in the installation, measurement and ramification of these pollutants through highly sophisticated machines.