Which is the largest unicellular organism

Protozoa is the fastest living thing in the world

A single-celled organism, only around a micrometer in size, is the fastest living being in the world: In one second, the microbe Methanocaldococcus, which belongs to the group of archaea, covers almost 500 times its body length (bodies per second, body lengths per second = bps). For comparison:
A sports car at a similar speed is likely to be “flashed” on a motorway at more than 6,000 kilometers per hour. Researchers from the University of Regensburg report in the journal "Applied and Environmental Microbiology" that the single-cell organism is by far the fastest living thing in the world.

According to the researchers, speed is essential for the archaea to survive in order to be able to adapt to their extreme environmental conditions. Because many archaea live under extreme conditions near hot springs at the bottom of the deep sea. There, water with a temperature of up to 400 degrees Celsius shoots out of the underground. If they get caught in this jet, the unicellular organisms can be catapulted into the deadly cold water in the vicinity in a fraction of a second, say the researchers.

Speed ​​keeps single-cell organisms in the warm water area

Being able to swim quickly back into the warm zone is therefore vital for the archaea. "With their flagella, the archaea keep themselves in a zone that is optimal for them - between the deep sea with around two degrees Celsius and the interior of the spring outlet," explains Reinhard Wirth from the Archaea Center of the University of Regensburg. The thread-like flagella are not only a drive, but also an important tool when it comes to adhering to surfaces in the preferred growth zones.

The Regensburg scientists were able to observe different swimming styles in some archaea species. In addition to a very fast, more or less straightforward style, the archaea also master a slower zigzag course. They apparently use the latter when they are in the vicinity of surfaces. "The combination of the two swimming styles leads us to assume that archaea use their speed to stay in a habitat that is favorable for them and thus to survive," explains Wirth.

Swimming behavior observed in a special microscope

The swimming behavior of bacteria has been analyzed intensively in recent years. However, there have not yet been any similar studies on archaea. Wirth and his colleague Bastian Herzog investigated the swimming behavior of seven archaea species and one bacterium in their experiments. They observed the speed and movements of the unicellular organisms with the help of a thermomicroscope built at the university, a special microscope that enables examinations at temperatures of up to 95 degrees Celsius - and thus the temperature range preferred by the archaea.

The two archaea species Methanocaldococcus jannaschii and Methanocaldococcus villosus stood out in the experiments with their speeds: They reached 590 and 470 micrometers per second. Since M. villosus is half a micrometer smaller than M. jannaschii, it is faster in relation to its body size. (Applied and Environmental Microbiology, 2012; doi: 10.1128 / AEM.06723-11)

(University of Regensburg, February 29, 2012 - NPO)

February 29, 2012