Getting the biggest bang for the buck: bacteria adapt their composition to maximize growth
Microbes — nature's waste recyclers — play a crucial role in recycling nutrients necessary for plant growth and ecosystem sustainability. The nutrient recycling, however, is controlled by the nutritional demand of bacteria and other microbes — something that is poorly understood, despite its critical importance. A team of researchers from the International Institute for Applied Systems Analysis (IIASA) and the University of Vienna have discovered that bacteria seem to follow a growth maximization principle that can exert a large influence on ecosystem nutrient cycling.
A flexible cellular make-up allows bacteria to adjust the composition of their machinery to optimize their growth capacity while using resources efficiently. Although acting in their own best interest, this strategy enhances not only their own growth but also—unintentionally—the recycling of nutrients that benefit other members of the ecosystem, such as plants. The conclusions emerged from a new mathematical model that was confirmed by experimental evaluation. "Because the model is rooted in 'natural laws' of ecology and evolution, it not only describes the inner mechanics of these bacteria in a particular environment, but also shows how they will respond to changing environmental conditions," says lead author Dr Oskar Franklin from IIASA.
The model explains many observed patterns of microbial biomass composition. It also demonstrates when the widely used "growth rate hypothesis," on which both theories and experimental methods have previously been based, break down — for example, when microbial growth is limited by nitrogen availability.
The study provides a new ecological perspective on the composition of individual microbes and helps us to better understand how the very small microbes can influence very large scale nutrient cycling in ecosystems.
Photo: A transmission electron microscopy image of bacteria (P. carotovorum) used in the study. The dark blue centers of the cells contain the cellular machinery and pools of storage compounds, which both adapt to the external resource availability. (photograph by Edward K. Hall ©)
