Resource Allocation during Slow Growth in Thermophilic Acetogenic Bacteria

• Applicant: Dr. Franziska Maria Mueller
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504745114

For competitive growth, bacteria must distribute resources efficiently between catabolism, anabolism, and maintenance processes. The resource allocation model aims at determining how microbes distribute cellular resources between these processes and will help to understand how cells work on a systems level. Due to the high cellular concentrations and high energy demands for the production of proteins, proteome allocation accounts for most of the energy distribution. As some of the few examples so far, Escherichia coli and the archaeum Methanococcus maripaludis, which both inhabit fluctuating environments, use different resource allocation strategies. In E. coli, which has a flexible catabolism, more resources are channeled to ribosome and protein production by using shorter catabolic pathways with lower molar energy yields during fast growth. In M. maripaludis, with methanogenesis as the only catabolic pathway, the number of ribosomes and the catabolic proteome remain constant at different growth rates, probably enabling a fast reaction to fluctuating conditions. The proposed project aims at elucidating resource allocation in the thermophilic, acetogenic bacterium Thermoanaerobacter kivui. T. kivui has a more flexible metabolism than M. maripaludis but is limited compared to E. coli, and inhabits a stable environment. It can grow chemolithoautotrophically using the Wood-Ljungdahl-pathway but also chemoorganoheterotrophically using, e.g., glucose. Due to the differences in metabolism and habitat, a different mechanism for resource allocation is expected. T. kuvui will be grown under chemoorganoheterotrophic conditions at different growth rates in chemostats limited either catabolically or anabolically. Cells will be analyzed for different parameters such as cell size (which differs in many bacteria depending on the growth rate) and macromolecular content (DNA and RNA content, proteome). As a main focus, proteome analyses will be performed and will reveal the proteome allocation to sub-proteomes of different metabolic pathways. The total number of ribosomes and the proportion of active ribosomes will be determined for elucidating how T. kivui achieves the different protein production rates at the respective growth rates. These experiments will reveal the allocation of resources to different metabolic processes and the reaction of T. kivui to slow growth conditions on a systems level. Overall, this study will provide data on the resource allocation in slow-growing bacteria from stable environments, and, thus, help to elucidate their ecophysiology and strategies to react to resource constraints.The project will be conducted at the Spormann laboratory at Stanford University, where similar studies on M. maripaludis as well as projects with T. kivui have already been performed. For this project, I can build on my experience in research on bacterial metabolism, e.g., using proteome analyses, and research on metabolic networks on a systems level.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Alfred Spormann