A paradigm-shifting protozoan
This story is not about a specific place, but about a microscopic organism that lives in freshwater ponds and a discovery that reshaped our understanding of life's origins. The organism is Tetrahymena thermophila, a single-celled ciliate about 50 micrometers long. In the early 1980s, biochemist Thomas Cech was studying how RNA from Tetrahymena was processed inside the cell. He and his colleagues at the University of Colorado Boulder were trying to isolate the protein enzyme responsible for cutting out a segment of an RNA molecule and splicing the remaining ends back together.
To their astonishment, they found that the RNA molecule could perform this cutting and splicing action all by itself, with no proteins present. This was a revolutionary finding. The central dogma of molecular biology held that DNA stored information and proteins performed the chemical work of the cell. RNA was seen merely as a messenger between the two. Cech's 1982 discovery showed that RNA could also be a biological catalyst, a role previously thought to be exclusive to proteins. These catalytic RNA molecules were named "ribozymes."
The RNA world
At the same time, Sidney Altman at Yale University was studying an enzyme called RNase P, which consists of both a protein and an RNA component. His research demonstrated that the RNA part of the enzyme was the active, catalytic unit. For their independent discoveries of the catalytic properties of RNA, Cech and Altman shared the 1989 Nobel Prize in Chemistry.
The existence of ribozymes provided the first strong experimental evidence for the "RNA world" hypothesis. First proposed in the 1960s, this theory suggests that the earliest forms of life on Earth relied on RNA for both storing genetic information and catalyzing the chemical reactions needed to sustain life. In this scenario, RNA acted as both the chicken and the egg, resolving the question of whether proteins or DNA came first. Life later evolved to use the more stable DNA for genetic storage and the more versatile proteins for catalysis, leaving ribozymes as molecular relics of this ancient biological era. Tetrahymena is an important model organism in labs today, contributing to discoveries about chromosomes, telomeres, and gene function.