In the article Ribosome Composition Maximizes Cellular Growth Rates in E. coli published July 8th in the journal Physical Review Letters, Zuckerman Postdoctoral Scholar Sarah Kostinski, together with her adviser Dr. Shlomi Reuveni, offer an explanation to a long-standing, unanswered mystery: Why is the bacterial ribosome made up of protein and RNA in an almost perfect 1:2 proportion?
Using mathematical analysis, Dr. Kostinski, who studies statistical and biological physics at Tel Aviv University, has shown that this ratio is special because it allows bacterial cells to maximize their growth rate and gain an evolutionary advantage. The ribosome, familiar to Israelis from Professor Ada Yonath’s Nobel Prize in Chemistry, is the biological machine responsible for building all proteins in a cell. Proteins, in turn, are responsible for performing a host of essential cell functions. Ribosomes are thus critical to cellular life.
Dr. Kostinski developed a mathematical model which shows that an excess of either protein or RNA in the ribosome causes cells to grow too slowly. Therefore, an optimal combination of protein and RNA is required. To determine the exact composition, Dr. Kostinski used data of biological parameters observed in E. coli bacteria (a species commonly found in our intestines). She discovered that a protein to RNA mass ratio of 1:2 – which is the actual ratio in the ribosome – maximizes the rate of cellular growth, regardless of environmental conditions. Since the same ratio also holds for the ribosomes of other bacteria, the conclusions of the study appear to be general, and not specific to only E. coli bacteria. The study also revealed a series of mathematical laws which govern cell growth.
“Sarah’s work is unique, and I’m sure it will leave a significant imprint on the field,” said Dr. Shlomi Reuveni of Tel Aviv University, who co-authored the article. “Particularly impressive is the fact that she joined my group without any background in biology and succeeded in such a short time to reach the forefront in her research field. She was able to provide a solution to such a fundamental scientific problem using a combination of mathematical and physical tools she acquired in her previous studies.”