How tiny do you have to be to classify as the world’s smallest organism? About 400 millionth of a millimeter say scientists in Regensburg, Germany.
Nanoarchaeum equitans is so small you can barely see it with a microscope
The honor of being the world’s smallest organism goes to a bacteria with the unusual name "ancient dwarf who rides the fire ball". Of course the microbe sounds much more impressive when called by its Latin name Nanoarchaeum equitans, but the scientific nomenclature doesn’t quite convey the same essence. And it’s exactly the unusual nature of the "riding dwarf" that makes it so fascinating for scientists.
Found in 120-meter (394 feet) deep waters off the coast of Iceland, the miniscule bacteria is 160 times smaller than the common human intestinal bacteria E-coli, approximately the size of a small pox virus. It prefers warm conditions, and thrives in temperatures close to 100° Celsius (212 ° F) or in the climate-controlled laboratory at the University of Regensburg.
The microbe gets its unique nickname from its tendency to latch on to or "ride" the surface of another microbe with the name Ignicoccus ("fire ball")
The German scientists don’t exactly know why the Nanoarchaeum chooses to hitch-hike on the back of another microbe. Professor Karl Stetter, who’s leading up the research project, suspects that the larger organism produces "some kind of substance the little one needs to survive". Stetter and his Regensburg team of micro-biologists are still looking for the exact answers.
So far they've found out quite a bit about the world’s tiniest creature.
With only some 500,000 genetic building blocks, the Nanoarchaeum has the smallest genetic code of all living cells. Two American companies, Celera Genomics and Diversa, have teamed up with the German scientists to unravel the tiny microbe’s genetic code. In doing so the Regensburg team hopes to discover important keys to the minimal genetic make-up required for sustaining life.
"We want to find out what is absolutely necessary for life," Professor Stetter explains, and adds that the Nanoarchaeum has at the most 400 different genes.
Although many viruses are smaller than the "riding dwarf" bacteria, scientists don’t count them as real living organisms. Unlike bacteria, viruses cannot reproduce on their own. They require the help of cells which they attack and take over, sucking out all life-giving functions.
Small but significant
The world’s smallest organism might have another claim to fame by being as old as life itself. Scientists researching the bacteria say it has been around since the early days of the Earth, and has survived the extreme conditions the planet has undergone in the last several millennia.
The Nanoarchaeum belongs to a group of so-called archae-bacteria (hence the Latin suffix). These bacteria are believed to date back to the formative ages of the Earth. Some are still found today in regions of the planet where the environment resembles that of a billion years ago, such as volcanoes, geysers, and hot sulfur springs.
Geysir in Iceland
The "riding dwarf" was discovered in a sample taken by a submarine near the Kolbeinsey riff, a volcanic region in the Atlantic, north of Iceland. Here, at the point where the European and American continental plates butt against each other, lava pours out and mixes with the water. Geologists say the conditions found in the area are similar to those found 3.8 billion years ago.
Professor Stetter and his colleagues believe the Nanoarchaeum, which thrives in the Kolbeinsey riff, is a type of "living fossil left over from the beginnings of life."
The scientists in Regensburg are convinced that their discovery of the "riding dwarf" is a breakthrough in understanding the biological history of the earth. So far there are three large branches of organisms: the Eukaryonten, which includes all higher forms of organisms; the bacteria; and the archae-bacteria. But Nanoarchaeum equitans is so "completely different from everything else", Professor Stetter says, that it forms a new group under the archae-bacteria.
The "ancient dwarf who rides the fire ball" has its world debut in this month’s edition of the British science journal "Nature".