Design and construction of electrogenic cell-based biosensors for pathogens and toxins

The traditional laboratory-based analytical assays for bacterial pathogens and environmental toxins are expensive, time consuming and normally require specialised personnel and complex (expensive) equipment. This restricts their use in resource limited rural areas and developing countries where lack sufficient skilled personnel and healthcare facilities to rapidly identify the risks. There is therefore an urgent need to provide simple cost effective, fast on-site sensing solutions for pathogens and toxins associated with fatal bacterial infections and contaminated daily resources.

For example, Vibrio cholerae bacteria contaminated water or food are typically responsible for the diarrheal illness cholera that can result in severe dehydration and even death within a matter of hours. Pseudomonas aeruginosa, commonly found on the surface of medical equipments such as catheters, is an opportunistic human pathogen and can be fatal for immunity compromised population. Arsenic contamination of groundwater is found in many places in the world, especially in Bangladesh where more than half of the population are facing the risk of arsenic poisoning which can cause cancers and various skin diseases. A simple, cost effective sensing solution that can accurately and rapidly report these severe health hazards will be vital to prevent the prevalence of these diseases and contribute to improved public health and quality of life.

In this project we will establish a route to develop autonomous cell-based biosensors with direct digital electrical output for cost effective, on-site detection of pathogens and environmental toxins associated with fatal bacterial infectious diseases or contaminated resources. Different genetically coded sensors will be constructed and placed inside living benign gut bacteria Escherichia coli to monitor the appearance of specific toxin or fingerprinting molecules secreted by pathogen. The transduced sensory signals then further undergo amplification and modulation via customised genetic circuits to enhance sensing sensitivity and selectivity. Upon the detection of target pathogen or toxin, the genetically engineered bacterial cells will switch on the production of an electron shuttle to generate electrical power in a device known as microbial fuel cell, which utilises the modified bacteria to convert organic matter into electricity. As a result, autonomous cellular biosensors are constructed with the ability to power and report the associated pathogen or toxin levels to electronic systems without the use of specific assay equipment.

The research builds a synthetic electron conduit between the currently less integrated cellular and electronic systems and will find many applications in environmental, agricultural and medical settings. The project will also contribute new design tools and methods, novel regulatory components and devices to the emerging field of deploying non-native biological systems in living microbes for repurposed actions of benefit to man.

In this project we will design and construct electrogenic cellular biosensors for cost effective, on-site detection of bacterial pathogens and environmental abiotic and biotic toxins. Using a combined biological and engineering approach, various exchangeable genetic encoded sensors, modular genetic signal processing circuits and electrical power generation output modules will be engineered and combined to program Escherichia coli in a microbial fuel cell setup. Upon the detection of target pathogen or toxin by the specific input sensors, the genetically engineered cells will switch on the production of an efficient electron mediator in the fuel cell, which then generates electricity to power and report to the associated electronic circuits with direct digital electrical output. As a result, autonomous self-powered cellular biosensors are constructed with the ability to report the associated pathogen or toxin levels to electronic systems without the use of specific assay equipments. The project will build a close interface between the currently less integrated cellular and electronic systems that could find many applications in environmental and medical settings, and provides novel regulatory components and modules as well as new circuit design tools and methods to the emerging field of synthetic biology.

The traditional laboratory-based analytical assays for bacterial pathogens and environmental toxins are expensive, time consuming and normally require specialised personnel and complex (expensive) equipment. This restricts their use in resource limited rural areas and developing countries where lack sufficient skilled personnel and healthcare facilities to rapidly identify the risks. There is therefore an urgent need to provide simple cost effective, fast on-site sensing solutions for animal or human pathogens associated with fatal bacterial infections caused through the actions of organisms such as Vibrio cholerae (causative marine organism for cholera), P. aeruginosa (lethal hospital pathogen for immuno-compromised patients), and toxins associated with contaminated daily resources such as arsenic (prevalent in contaminated groundwater in Asia).

The central aim of the proposed research is to construct an autonomous self-powered sensing device that can specifically and sensitively detect a target animal or human health hazard (e.g. arsenic, P. aeruginosa and V. cholerae) without using complicated laboratory equipment. The proposed project is based on combining specific pathogen or toxin-responsive input sensors, modular genetic logic circuits and an electrical power generation output module to program Escherichia coli to detect various bacterial pathogens and environmental toxins via a direct electrical output. The cell-based biosensor will work in microbial fuel cell mode and be self-powered to accomplish the sensing tasks with a digital electrical output indicating the hazard level, and so facilitate cost effective, on-site detection without the use of elaborate assay equipment.

The research therefore will provide a simple, cost effective sensing solution that can accurately and rapidly report selected severe health hazards and is vital to prevent the prevalence of the associated diseases and contribute to improved public health, wellbeing and quality of life. In addition, the research deploys a novel synthetic biology approach to build a close interface between the currently less integrated cellular and electronic systems which will open new doors to study and assay diverse intracellular activities via more accessible electronic devices and systems. Finally, the project will also generate new circuit design tools and methods, novel regulatory components and modules to assist the maturation of the emerging field of synthetic biology.

The work will provide proof of principle for new approaches which are of high value to the community working in bio-sensing, and will reveal new exploitable features of established regulatory components arising from basic molecular microbiology. The work will be of importance to researchers in academia working at the interface of life sciences and engineering, and those in biotechnology and biosensing industry. To those interested in therapeutic intervention the work will provide an example of a translational outcome from coupling basic sensing and gene control circuits to the re-purposing of a model microorganism. Thus potential patentable designs and technologies could be generated that might be of great interest to biotechnological sector and we will patent promising designs as they become available.