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D 2 - Tobias Erb

Novel principles in bacterial central carbon metabolism: Linking environmental signals and metabolic responses in alphaproteobacteria

Dr. Tobias Erb
Max Planck Institute for Terrestrial Microbiology

Karl-von-Frisch-Straße 10
35043 Marburg

Phone: +49 - 6421 - 178 426

Research summary

The vast majority of carbon compounds in the environment are degraded into acetyl-CoA. Acetyl- CoA is a central control point in metabolism, because it serves in energy conservation, as well as in biomass formation. To achieve optimal growth, organisms need to tightly balance the flux of acetyl-CoA between these two processes. For more than 50 years, Escherichia coli served as a model to understand the metabolic and regulatory mechanisms that control acetyl-CoA metabolism in response
to environmental changes, such as fluctuating nutrients. To convert acetyl-CoA into biomass, E. coli uses the glyoxylate cycle, which is embedded into an elaborate transcriptional and posttranslational network. We recently discovered the ethylmalonyl-CoA pathway, a completely novel acetyl-CoA assimilation strategy that is fundamentally different from the glyoxylate cycle. The ethylmalonyl-CoA pathway is used by many environmentally important and abundant microorganisms, such as Streptomycetes and many alphaproteobacteria. Pilot studies in our lab show that the structure and regulation of the ethylmalonyl-CoA pathway strongly differ from the glyoxylate cycle in E. coli.

In this project we will characterize the metabolic and regulatory diversity of acetyl-CoA metabolism in selected alphaproteobacteria, in particular Paracoccus denitrificans. P. denitrificans encodes for both, the glyoxylate cycle and the ethylmalonyl-CoA pathway, which makes it an ideal system to study both assimilation strategies side-by-side in one model organism. We will focus on studying the environmental factors and signals controlling acetyl-CoA assimilation in P. denitrificans, as well as the dynamic response of acetyl-CoA metabolism upon perturbation. Our studies will extend our knowledge beyond the E. coli “textbook” example and unravel novel strategies in central carbon metabolism that enable the adaption of microorganisms to an ever changing environment.