Connecting single-cell ATP dynamics to overflow metabolism, cell growth and the cell cycle in Escherichia coli

Adenosine triphosphate (ATP) is a universal energy-carrying molecule that cells consume and regenerate in vast amounts to support growth. Despite this high turnover, bacterial cultures maintain a similar average concentration of ATP even when the carbon source conditions lead to large differences in population growth rate. What happens in individual bacterial cells is, however, less clear. Here, we use the QUEEN-2m biosensor to quantify ATP dynamics in single Escherichia coli cells in relation to their growth rate, metabolism, cell cycle, and cell lineage. We find that ATP dynamics are more complex than expected from population studies and are associated with growth rate variability. Under a nutrient-rich condition, cells can display large fluctuations in ATP level that are partially coordinated with the cell cycle. Abrogation of aerobic acetate fermentation (overflow metabolism) through genetic deletion considerably reduces both the amplitude of ATP level fluctuations and the cell cycle trend. Similarly, growth in media in which acetate fermentation is lower or absent results in reduction of ATP level fluctuation and cell cycle trend. This suggests that overflow metabolism exhibits temporal dynamics, which contributes to fluctuating ATP levels during growth. Remarkably, at the single-cell level, growth rate negatively correlates with the amplitude of ATP fluctuation for each tested condition, linking ATP dynamics to growth rate heterogeneity in clonal populations. Our work highlights the importance of single-cell analysis in studying cellular energetics and its implication to phenotypic diversity and cell growth.