Meet the extremophiles

An extremophile is an organism that can thrive under extreme physical or geochemical conditions. Situations in which a human couldn’t survive for a microsecond. The word ‘extremophile’ comes from the Latin word ‘extremus’ (utmost or furthest) and the Greek word ‘philiā’ (beloved). In the 1980s and ‘90s, biologists discovered that microbial life can display astonishing flexibility when it comes to living in extreme conditions. Most extremophiles are also microorganisms, like fungi, algae, bacteria and especially archaea.

Anywhere is possible

There are different types of extremophiles. Some live in extremely high temperatures (thermophiles), and others in extremely low temperatures (psychrophiles). Some types exist in places with extremely high atmospheric pressure (barophiles) while others can survive in extremely salty conditions (halophiles). You’ve got types that thrive in low pH environments (acidophiles) and those who need high pH conditions (alkaliphiles). Others live where there’s high concentrations of heavy metals, or even high doses of radioactivity.

• There are bacteria that live 800 metres under the ice in Antarctica, and 11 kilometres deep in the Mariana Trench – the deepest place on earth.
• There have even been microorganisms discovered that live 1,900 metres deep in the bedrock under 8,500 metres of ocean.
• Other extremophiles can only live in water temperatures around 120 degrees Celsius, or 2 degrees Celsius.
• Still others live in (substantially) pure sulphuric acid, for example, in a volcanic lake.

Toughest bacterium

The most extreme extremophile that is known at the moment is the Deinococcus radiodurans. This microbe can survive extreme cold, drought, thin air and acid. It has even been found on the walls inside nuclear reactors, where the radioactivity would be instantly fatal for humans. No wonder this bacterium has earned a place in the Guinness Book of World Records as the world’s toughest.

Suspended animation

There are also microbes that don’t necessarily seek out extreme conditions, but can survive for periods of time in extreme environments. The most well-known is the water bear (Tardigrada). When conditions become extreme, the water bear goes into a state of suspended animation (fake death) called cryptobiosis. It rolls up into a barrel-like shape, reduces its metabolism to 0.01% of its normal rate and dries itself out.

During this fake death, its body contains only about 3% of its normal amount of water. In this state, the water bear can survive in a variety of extreme conditions for up to 10 years. As soon as the environment takes on a more normal state, the water bear absorbs moisture and comes ‘back to life’. This microbe even survived a journey into outer space for ten days without any protection.