Self-propelled microscopic organisms are ubiquitous in water. Such organisms’ motility depends on hydrodynamic and physical factors related to the rheology of the surrounding media and biological factors depending on the organisms’ state and well-being. Here we demonstrate that the swimming speed of Paramecium aurelia, a unicellular protozoan, globally found in fresh, brackish, and salt waters, can be used as a measurable frugal indicator of the presence of pollutants in water. This study establishes a significant and consistent relationship between Paramecia’s swimming speed and the presence of five different organic and inorganic contaminants at varying concentrations centered around drinking water thresholds. The large size and ubiquity of the targeted microorganism, the avoidance of reagents or specialized tools for the measurement, and the simple data collection based on an object tracking algorithm enable the automatization of the assessment and real-time results using globally available technology.
Manipulating microorganisms with inherent motility is a challenging yet significant aim with implications in many biological, environmental, and technological applications. Many microorganisms that are broadly available in nature can be used as self‐powered systems that can be directed with external stimuli. Paramecium is a unicellular protozoan that exhibits a negative galvanotaxis where the cell follows the direction of weak electric fields. Here, the galvanotactic behavior of Paramecia is studied to achieve the precise manipulation of these organisms. Using a specially devised microfluidic chip and computer vision, unprecedented levels of manipulation and isolation of Paramecia are demonstrated, enabling their integration, use, and study in micro‐electromechanical systems.
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