Abstract: There are many ways that metabolic flux can be coupled to organism growth and survival. One emerging research area documents metabolic variability in genetically identical populations. In this talk I will discuss our recent efforts towards understanding heterogeneity in isogenic cells by coupling nanoSIMS isotope data with metabolic modeling. Our results suggest that intra-population metabolic coupling exists between cells, opening a new research area of “isogenic ecology”. In the second part of the talk, I’ll move to metabolic variability as it exists across organisms. I will discuss an approach to finding nutrients required for growth using the network expansion algorithm. In our preliminary analyses, we find genome size and enzyme compliment shape nutrient requirements across taxonomic diversity.