Growth, metabolic partitioning, and the size of microorganisms.
Population growth rate is a fundamental ecological and evolutionary characteristic of living organisms, but individuals must balance the metabolism devoted to biosynthesis and reproduction against the maintenance of existing structure and other functionality. Here we present a mathematical model that relates metabolic partitioning to the form of growth. The model captures the observed growth trajectory of single cells and individuals for a variety of species and taxa spanning prokaryotes, unicellular eukaryotes, and small multicellular eukaryotes. Our analysis suggests that the per-unit costs of biosynthesis and maintenance are conserved across prokaryotes and eukaryotes. However, the relative metabolic expenditure on growth and maintenance of whole organisms clearly differentiates taxa: prokaryotes spend an increasing fraction of their entire metabolism on growth with increasing cell size, whereas eukaryotes devote a diminishing fraction. These differences allow us to predict the minimum and maximum size for each taxonomic group, anticipating observed evolutionary life-history transitions. The framework provides energetic insights into taxonomic tradeoffs related to growth and metabolism and constrains traits that are important for size-structured modeling of microbial communities and their ecological and biogeochemical effects.
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ckempes@gmail.com
Christopher P
CP
Kempes
Stephanie
S
Dutkiewicz
Michael J
MJ
Follows
D005075:Biological Evolution; D053898:Biosynthetic Pathways / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D056890:Eukaryota / Q000166:cytology / Q000254:growth & development*; D008954:Models, Biological; D011156:Population Density; D011387:Prokaryotic Cells / Q000166:cytology / Q000502:physiology*; D013045:Species Specificity