NICOP - Bacterial flagellar motor as fast synthetic biosensor
Abstract
One of the most compelling areas of Synthetic Biology is in engineering biological organisms to provide a new range of sensor modalities, capabilities, and manufacturing technologies. The sensor industry sees great promise in using whole-cell-based biosensors for a large and diverse set of targets: from toxins, pathogens, and explosives to human-health related biomarkers. Whole-cell based biosensors, often using bacterial cells as the cellular chassis, have been developed but they respond slowly– at best ~6 minutes and often more than 30 minutes – which limits their value for navigation or rapid detection. However, many bacteria have evolved a sensitive and fast navigational network, with response times of 1-3 seconds and the ability to direct bacterial cells toward nM-?M concentrations of specific chemicals. For example, Escherichia coli swims by rotating several flagella randomly distributed along the cell body. At the base of each flagellum is the bacterial flagellar motor, a rotary molecular machine that couples proton motive force (PMF) to the rotation of flagellar filaments. Membrane bound proteins, called chemo-sensors, can sense various environmental signals and activate a signaling cascade that influences the rotation of the motor. Together, these components comprise the chemotactic network. By controlling the direction of motor rotation, E. coli can accumulate in areas favorable for their survival. This behavior, called taxis, has long been a subject of scientific investigation. Taxis serves a variety of purposes: it helps bacteria seek out nutrients and avoid toxic substances, to identify thermal and oxygen gradients, and aids pathogenic bacterial species to better identify and infect their hosts. Recently, it has been shown that the motor is not only an output of a sensory response but also a sensor itself. It can modulate its speed and direction of rotation in response to mechanical stimuli. Motors have been reported to respond to high hydrostatic pressure and decrease in temperature by changing rotational direction and speed. In addition, we have recently begun characterizing the response of the chemotactic network to changes in external osmolarities, such as those caused by high sugar concentrations. Under these conditions, the motor also changes speed and the direction it rotates. The findings open the possibility of using the bacterial flagellar motor and the chemotactic network as a fast synthetic biosensor. To do this a detailed characterization of the motor signal response to the following stimuli characteristic for marine environments is needed: (a) response to shear flow; (b) response to salinity changes; and (c) response to combinations of multiple signals. In this project, relying on our unique ability to combine state-of-the-art single motor and microfluidics experiments with the latest synthetic biology and molecular cloning techniques, we will measure the speed and direction of a single motor while simultaneously exposing it to shear flow and changes in external salt concentrations. Our goal is to obtain characteristic motor response functions to each of these stimuli singly and then in combination. Once we have obtained the characteristic response functions, we will be able to engineer the components of the bacterial chemotactic network to tailor the motor response function to best suit our goal, which is to use the motor as a fast-response biosensor for navigational purposes.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N629091812064
Entities
People
- Teuta Pilizota
Organizations
- Office of Naval Research
- United States Navy
- University of Edinburgh