Tiny "fire amoeba" grows in very hot water

Scientists have found a new kind of amoeba^*1 that can grow in very hot water. They named it Incendiamoeba cascadensis, and they call it the "fire amoeba." A team supported by NASA, the space agency of the United States, wrote about it in the science magazine Cell on Tuesday, September 22. The leader of the study is Beryl Rappaport, a graduate student^*2 at Syracuse University.

The team took the amoeba from hot spring^*3 water in Lassen Volcanic National Park in California. In the lab^*4, the amoeba grew by cell division^*5 at 63 degrees Celsius (145 degrees Fahrenheit). This is a new record. The fire amoeba is a eukaryote^*6. Before this, the hottest temperature for a growing eukaryote was 60 degrees Celsius (140 degrees Fahrenheit). Some fungi^*7 and some red algae^*8 held that record.

Above 63 degrees, the fire amoeba stops growing. But it can still move and look for food up to 64 degrees Celsius (147 degrees Fahrenheit).

This finding surprised scientists. They thought the membranes^*9 around the small parts inside a eukaryote cell could not stay stable above 62 degrees Celsius (144 degrees Fahrenheit). The fire amoeba shows that this idea was wrong.

The team also studied the genome^*10 of the amoeba. In the heat, some genes^*11 became more active. Some of these genes keep the DNA^*12 stable and stop it from breaking down. Others sense the world outside the cell. Others keep proteins^*13 in the right shape when it is hot. The team also found that some of the amoeba's proteins have a strong positive charge^*14 on their surface. Bacteria^*15 and archaea^*16 that live in very hot places have proteins like this too.

Similar pieces of DNA have been found in hot places around the world, for example in New Zealand and in Yellowstone National Park. So there may be other heat-loving amoebas like this one all over the world.

Alison Olcott, a scientist in the astrobiology^*17 program at NASA headquarters, said the discovery helps us understand where complex life can live, and how much of it there can be. Rappaport said that heat is only one part of the story. To live, a living thing also needs the right acidity^*18, oxygen^*19, pressure^*20, water, and food.

1. *1 amoeba: a very small living thing made of one cell that can move and change its shape
2. *2 graduate student: a student who is doing more study at a university after finishing a first degree
3. *3 hot spring: a place where hot water comes up out of the ground
4. *4 lab: a room where scientists do tests
5. *5 cell division: when one cell splits into two cells; this is how tiny living things grow in number
6. *6 eukaryote: a living thing whose cells have a center part and other small parts inside, like plants, animals, and fungi
7. *7 fungi: living things like mushrooms and mold
8. *8 algae: very simple plant-like living things that live in water
9. *9 membranes: very thin skins that go around a cell or around the parts inside a cell
10. *10 genome: all the DNA in a living thing
11. *11 genes: small parts of DNA that tell a living thing how to grow and work
12. *12 DNA: the material inside cells that carries the instructions for a living thing
13. *13 proteins: important building blocks inside living things
14. *14 positive charge: one of the two kinds of electricity that a very small thing can carry
15. *15 bacteria: very small living things made of one simple cell
16. *16 archaea: very small living things made of one cell; they look like bacteria but are a different group
17. *17 astrobiology: the study of life in space and on other planets
18. *18 acidity: how sour or acid a liquid is
19. *19 oxygen: the gas in the air that living things need to breathe
20. *20 pressure: how hard something pushes on a thing