Investigations of the Response of Swimming Paramecia to Variations in their Apparent Weight (original) (raw)
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Models suggest that mechanical interactions alone can trap swimming microorganisms at surfaces. Testing them requires a method for varying the mechanical interactions. We tuned contact forces between Paramecia and surfaces in situ by varying their buoyancy with nonuniform magnetic fields. Remarkably, increasing their buoyancy can lead to ∼100% trapping at lower surfaces. A model of Paramecia in surface contact passively responding to external torques quantitatively accounts for the data implying that interactions with a planar surface do not engage their mechanosensing network and illuminating how their trapping differs from other smaller microorganisms.
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Earth's gravity exerts relatively weak forces in the range of 10–100 pN directly on cells in biological systems. Nevertheless, it biases the orientation of swimming unicellular organisms, alters bone cell differentiation, and modifies gene expression in renal cells. A number of methods of simulating different strength gravity environments, such as centrifugation, have been applied for researching the underlying mechanisms. Here, we demonstrate a magnetic force-based technique that is unique in its capability to enhance, reduce, and even invert the effective buoyancy of cells and thus simulate hypergravity, hypogravity, and inverted gravity environments. We apply it to Paramecium caudatum , a single-cell protozoan that varies its swimming propulsion depending on its orientation with respect to gravity, g . In these simulated gravities, denoted by f gm , Paramecium exhibits a linear response up to f gm = 5 g , modifying its swimming as it would in the hypergravity of a centrifuge....
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Mechanics of membrane–cytoskeleton attachment in Paramecium
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