Living in hot environments also brings unique challenges to which our microorganisms need to adapt. We have, as a reminder, our thermophiles and our hypothermophiles. Thermophiles are classified as being any optima that is above 80 degrees Celsius.
Our bacteria grow up to about 95 degrees Celsius. degrees Celsius. So bacteria are around 95. Eukarya are about 65 degrees Celsius.
So anything above 95 has to be an archaea. It's not that they, you know, you don't find bacteria at this range, et cetera, and you don't find archaea at these ranges, but those are the upper limits for those particular organisms. And we find them in our... undersea hydrothermal vents. We find them in hot springs that we can see here.
This is the very famous prismatic pool here at Yellowstone. And they have to produce heat-stable macromolecules, particularly their proteins, and they also have to stabilize their memories. So let's talk about their particular adaptations. So we're going to start with our proteins or our enzymes. And first thing is they usually have amino acid substitutions.
So They allow them then to fold in a particular way. So you'll see amino acid changes in critical places, and they fold in particular ways and become much more heat stable. They have a greater number of ionic bonds.
So that's another adaptation. And that happens between the basic and acidic amino acids. And that means that they pack that internal environment to be very, very hydrophobic. So there's much more hydrophobic interactions as well that are occurring. And that means that these proteins resist unfolding in these high temperature.
Now, in particular, you may have come across an enzyme called TAC polymerase. And TAC actually comes from a bacterium called Thermos Aquaticus. So that's why I underline TAC because it's actually an abbreviation of that organism, and that is used for PCR.
So if you've had a PCR for COVID or something else, then you have taken advantage of one of these thermophiles. Now, in addition to these protein modifications, they have membrane adaptations. So let's talk about a few of those membrane adaptations. The first thing that we can consider is that they usually have longer chains, so they're longer.
And they tend to have many more saturated fatty acids. And that allows their membranes to remain stable and functional. And then lastly, remember in archaea, we have that phyantel and monolayer membranes, which help them resist that cell lysis. And those are much more stable as well.