Researchers at the Whitehead Institute in Cambridge, Mass., together with colleagues at MIT, the Marine Biological Laboratory in Woods Hole, Mass, and University of Illinois, Chicago, have discovered an important mechanism of action of flagellum-like structure of Vorticella convallaria, a protozoan. The discovery might have influence on the development of future nanomedical technologies:
Scientists have known about this nano-spring for roughly 300 years, ever since Anton van Leeuwenhoek first observed the protozoan, Vorticella convallaria, through a hand-made microscope. The spring in the unicellular Vorticella is a contractile fiber bundle, called the spasmoneme, which runs the length of the stalk. At rest, the stalk is elongated like a stretched telephone cord. When it contracts, the spasmoneme winds back in a flash, forming a tight coil. To find out how strongly Vorticella recoils, France and colleagues [Danielle France, a graduate student in the Whitehead Institute and a member of MIT’s Division of Biological Engineering -ed.] used a unique microscope to apply an extra load to the spring. The microscope, developed by Shinya Inoue and colleagues at the Marine Biological Laboratory in Woods Hole, MA, uses a spinning platform to increase the centrifugal force exerted against the protozoan.
In the past, researchers have measured Vorticella’s ability to recoil its spring at 40 nano newtons of force and at a speed of eight centimeters per second, units of measurement that are typically too large to be relevant for biological processes. (These measurements, when scaled up to the size of a car engine, prove the Vorticella to be the more powerful of the two.) However, when France used the centrifuge microscope, she discovered that the spring was able to recoil against as much as 300 nano newtons of force.
France and colleagues also made an important link between the engine’s fuel, calcium, and a major protein component of the stalk. This protein, centrin, belongs to a class of proteins that can be found in organisms ranging from green algae to humans. When the researchers introduced an antibody for the Vorticella centrin into the cell, the spring was no longer able to contract, indicating that the cell uses a powerful centrin-based mechanism, one that is unlike other known cellular engines.