Incentives to define lists of genes that are essential for bacterial survival include identification of potential targets for antibacterial drug development, genes required for rapid growth for exploitation in biotechnology, the discovery of new biochemical pathways and understanding of the nature and origin of life.

Traditional foraging models are based primarily on a single dietary currency, usually energy or less commonly protein. I will introduce a geometric framework for examining the role of macronutrient balance in the dietary responses of animals, and distinguishing it from energy.