Cell growth, gene expression, and their interdependence

Cell growth, gene expression, and their interdependence. If given ample food, bacteria proliferate exponentially. If given little or low-quality food, bacteria proliferate sluggishly. Behind that adjustable growth lies a complex web of interconnected molecular pathways, the elucidation of which is a major goal in biology. But, as Terence Hwa of the University of California, San Diego, and his collaborators demonstrate, you can accurately model the outcome of those complex reactions without knowing the details. Hwa and his colleagues based their model on experiments that revealed the relationships between proliferation rate, nutrient quality, and the ratio of RNA to protein inside the bacteria. That ratio, which is straightforward to measure, is significant because all proteins are made by RNA-rich ribosomes: The more ribosomes in a cell, the faster the cell can grow and multiply. The mathematical relations that emerged from the UCSD team’s analysis are simple and linear, and they reflect...