Trait-based approach to bacterial growth efficiency

Bacterial growth efficiency (BGE) is the proportion of assimilated carbon that is converted into biomass and reflects the balance between growth and energetic demands. Often measured as an aggregate property of the community, BGE is highly variable within and across ecosystems. To understand this variation, we used a trait-based approach with 20 bacterial isolates enriched from lake communities to determine how consumer and resource identity affect BGE. We used phenotypic and genomic approaches to characterize the metabolic physiology of each isolate and test for predicted trade-offs between growth rate and efficiency. Across resource types, 20 % of the variation in BGE could be attributed to the coarse-scale taxonomic resolution of the isolate, while 58 % of the variation could be explained by isolate identity. Resource identity explained a relatively small amount of variation (7 %) in BGE across isolates but accounted for > 60 % of the variation within an isolate alone. Metabolic trade-offs and genomic features associated with BGE suggest that BGE is a species trait, which regardless of resource environment, contributes to variation in BGE. Genomic and phylogenetic information from microbiomes may help predict aggregate community functions such as BGE to better understand the fate of organic matter resources in ecosystems.