When searching for extraterrestrial life, we consider the temperature of the planet or satellite in question. They usually need to be at a suitable distance from their star. Not too far, as it would be cold, nor so close that the temperature would be scorching. The habitable zone is generally one where temperatures can keep water liquid, not frozen or in gaseous form. However, if we want to look for eukaryotic organisms, we tend to refine them further, because they combine very poorly with heat.
The record was 60 degrees Celsius, but now a team of scientists from Syracuse University has discovered an amoeba that is able to reproduce at 63 degrees Celsius and even recover its activity after 70 degrees Celsius. It may seem like a small difference, but it’s a big game changer.
Fire amoeba. The amoeba in question was found in hot water pools in Lassen Volcanic National Park (California). It resisted heat so well that it was named after it Incendiamoeba cascadensis And, more colloquially, as a fiery amoeba. There are several statistics to take into account when analyzing your resistance level. Initially, it can reproduce by cell division up to 63ºC. At 64ºC it is still active, although it no longer reproduces. Later, at 66ºC it remains partially active, although it begins to suffer heat effects. At 70ºC it is already inactive, but it can still be activated again. However, at 80ºC it dies completely.
Other thermophilic organisms. Extremophilous organisms are those capable of withstanding conditions considered extremely extreme. When these conditions are associated with high temperatures, they are considered thermophiles. There are thermophilic organisms that are much more heat resistant than the fire amoeba. For example, archaea Methanopyrus candlerii It can survive up to 110ºC. But there is a difference. Archaea, like bacteria, are unicellular prokaryotic organisms. This means that they are made up of a single cell, without a delimited nucleus. They are simple, so it is easy for them to withstand extreme conditions.
On the other hand, eukaryotes have a confined nucleus. If they also have organelles and more complex cellular machinery, like this amoeba, there are more structures that can fail due to heat, so they resist less. Until now, the record for the temperature a eukaryotic organism can withstand was held by some fungi and red algae, which reached approximately 60ºC. The fire amoeba surpassed them all.
his Modus operandi. The key to resistance to temperature lies in this amoeba’s genes. The scientists who discovered it found that it contained genes on one side that allowed it to repair DNA caused by heat damage. Furthermore, due to their structure, their proteins are more stable when the temperature increases. On the other hand, it has the ability to sense the environment and the heat that surrounds it, so that it can activate or deactivate the necessary genes at any moment.
More places to visit. As more and more extreme organisms are known, space expands where extraterrestrial life can be searched for. This fire amoeba tells us that, perhaps, there were planets that were ruled out for being too hot and that should not have been ruled out so quickly. Of course, we must remember that an organism can withstand heat very well, but not salinity, acidity or cosmic radiation.
At this point, Earth is the only planet that meets all possible habitable conditions. For all that, picking out possible worlds where life thrives isn’t as easy as measuring the temperature. However, now we can see that, at least as far as heat is concerned, we can extend the range a bit.
Picture | Beryl Rapaport
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