Mitochondrial ribosome content as a proxy for respiration

Quantifying cellular activities remains a major challenge across fields ranging from microbial ecology to biotechnology and biomedical sciences. Building on the well-established linear relationship between growth rate and ribosome content-the so-called microbial growth law-this study proposes using organelle ribosome content to infer metabolic activity. In exponentially growing yeast (Saccharomyces cerevisiae), including under overflow metabolism conditions, a strong linear correlation was observed between mitochondrial ribosome content and oxygen uptake rate, underscoring the potential of this approach. Additionally, under fully respiratory conditions, cytoplasmic and mitochondrial ribosome fractions were linearly correlated, whereas overflow conditions fell below this linear relationship, providing a means to identify such metabolic states. Although these findings require broader validation across additional species, organelle ribosome quantification may provide a promising proxy for deciphering cellular metabolism.