Tardigrade

The unusual suspects

Extremophiles in the spotlight

Life, it seems, comes in all shapes and sizes. Discoveries made in the past few decades have revealed that living things can make a home just about anywhere on Earth. Extremophiles, organisms that love extreme environments, help to shape our thinking about what could survive in other parts of the universe.

  • Thermophiles (extreme heat): The single-celled Pyrococcus furiosus, first found near a volcano in Italy, can withstand temperatures of 100°C. Its enzymes contain tungsten, which is unusual for biological molecules, and function optimally at this high heat.
  • Halophiles (extreme saltiness): Wallemia ichthyophaga, the most halophilic fungus known to exist, cannot grow without salt. High levels of salt allow the fungus to grow much bigger and to thicken its cell walls.
  • Radioresistant (extreme radiation): First discovered in a submarine hydrothermal vent, the microbe Thermococcus gammatolerans can rebuild its damaged chromosomes following exposure.

You may have noticed that these extremophiles are mostly bacteria (from the Archaea division). But animals can be extremophiles too. Arguably the hardiest is the tardigrade (also known as the ‘water bear’). It can cope with low or high pressure, hot or cold temperatures, very little water and huge amounts of radiation. It does this by going into a hibernation mode. In 2007 it became the first living organism to survive in the vacuum of space without any protection.

For a full list of the different types of extremophiles, see our table, and for some fascinating images, our image gallery.

Lead image:

A pregnant tardigrade shown from below.  

speciousreasons/Flickr CC BY NC

References

Downloadable resources

About this resource

This resource was first published in ‘Space Biology’ in June 2015.

Topics:
Cell biology, Genetics and genomics, Ecology and environment
Issue:
Space Biology
Education levels:
16–19, Continuing professional development