Extremophile Examples Beyond Our World

Looking to the stars in search of Microbes!

When I said microbes can be linked to anything on earth, I may not have been entirely truthful to you dear reader. However, I'm here today to set the record straight; the truth is microbes can be linked to anything in the Universe!

That's right, at the beginning of the month we journeyed to a time a long long time ago in a galaxy far far away to discuss midi-chlorians, jedi, and ticks as well as microbes, milk, and exotic Toniray Wine. As the month of May comes to a close, we will loop back around to the wonderfully fantastic (but totally real) field of Astrobiology.

Astrobiology aims to answer several fundamental questions of life that have forever plagued the thoughts of humanity. The main one is one every single person has thought about at one point in their life:

Are we alone?

There are 4000 planets in our galaxy and, still, we have not found any existence of life as we know it out there. But this does not mean there is no life, we just haven’t found any yet, or perhaps we aren’t looking through the right lens.

We owe our ‘living’ world to a handful of microorganisms that appeared on earth more than 3.7 billion years ago. These microbes had to survive scorching temperatures, toxic air, and extremely unfavorable conditions. Today, we can still find microbes that live in harsh environments, we call them extremophiles. There are two main categories of extremophiles: generalist and specialist. These names refer to the ability of the microbe to survive in either one extreme condition (a specialist) or multiple (a generalist). It is highly unlikely that these microbes are exactly as they were in the early days of earth. However, they give us great insight into how anything can survive in these harsh environments both on our planet and beyond.

One particularly important class of organisms for a model in astrobiology is Haloarchaea. These microbes produce blooms of vibrant colors including red, orange, and purple. These colorful blooms have often been seen from airplanes and on occasion, they can be Seen from space!

This group of microbes can survive in a variety of extreme conditions including:

Salinity (salt)

Temperature (both hot and cold)

No oxygen

Radiation (UV & ionizing)

Low pressure

Ph (both acidic and alkaline)

You probably have not traveled to any of these inhospitable locations, but they do exist on earth such as the deep sea or Antarctica. Although not exact, these inhospitable conditions mimic those of other planetary surfaces, making these extremophiles excellent models for potential life outside of earth.

Two extremophiles, Halobacterium sp. NRC-1 (from the solar salterns of San Francisco Bay) and H. lacusprofundi (from a hypersaline Deep Lake, Antarctica), have been compared. How did scientists compare them you ask? They shot these two microbes 35 km (~22 miles) high in the atmosphere to see if they would survive, now that’s a study I’d like to be a part of! Unsurprisingly, the species from Antarctica dealt with the cold better and was able to survive and grow after its journey to the stratosphere.

By delving deep within the genome and proteome (fancy word for proteins of an organism), scientists can reveal what allows these microbes to live in such places. ‘Normal’ organisms have neutral proteins, meaning they are neither acidic nor basic. However, proteins from these extremophiles are very acidic. So, what’s the benefit of acidic proteins? Let’s take salt for an example, when you eat too much salt you can retain extra water. For us, this has the potential of raising blood our pressure and leading to heart strain. For our cells, too much salt can cause osmotic pressure changes. If you don’t remember from high school, and I mean who does, osmosis is the diffusion of water across a membrane. Molecules (like salt) help regulate osmosis and it's important to keep an equilibrium, too much salt can cause proteins to shut-down and denature. If you live in extremely salty conditions like Halobacterium and H. lacusprofundi, you need to avoid this. The acidic proteins allow these microbes to stay hydrated and maintain function.

Mammoth Hot Springs

These microbes may be good models for both potential life forms on other planets as well as the study the evolution of life. But how could we detect life so far away? Most Haloarchaea produce pigments that may protect them from light and help them grow and repair. Pigments such as these may also provide a great starting point for astronomic detection of life on other planets. As technology improves, telescopes like LUVOIR and HabEx can see farther and better identify atmospheres from far away planets. Perhaps we would be able to detect pigments such as the ones we see from Haloarchaea. However, we need to better understand the pigments we have on earth to make sure we are accurate. Even then there is a high possibility for false positives.

So my question to you is: are we alone in the universe, or are we just unable to detect what’s out there? Also, Are there any other extremophiles out there that have been experimented on in outer space that we have not mentioned? Let us know by commenting or sending an email; we would love to hear from you!

1.DasSarma, S., DasSarma, P., Laye, V. J. & Schwieterman, E. W. Extremophilic models for astrobiology: haloarchaeal survival strategies and pigments for remote sensing. Extremophiles24, 31–41 (2020).