Exploring Bacterial Microcompartments to eEstablish Orthogonal Metabolism

Post genomic system analyses of apparently simple microbial life reveal an ever increasing complexity that must be managed in order to design reliable and robust cell factories. Managing this complexity using systems biology approaches is an attractive option but reduction of complexity (ROC) is the more promising solution. ROC could be achieved by a true de novo design of microbial cells built only from the essential components, or by sequential genome reduction of naturally evolved platform organisms.

Here, we introduce another ROC-concept, i.e. orthogonalisation of cellular metabolism (1). Recent developments in metabolic engineering and synthetic biology offer novel design principles towards the introduction of spatial orthogonality in living cells. Towards this goal, scaffolding of enzyme cascades is especially appealing due to the ease and flexibility of this design principle. Bacterial microcompartments (MCPs) are subcellular proteinogenic organelles found in a broad variety of bacteria (2). MCPs enclose proteins and enzymes of biosynthetic or biodegradative pathways and serve to improve multistep biosynthesis or to insulate (toxic) reaction cascades within cells. We demonstrate successful rerprogramming of bacterial microcompartments (MCPs) to enclose a b-galactosidase, an esterase and an oxidoreductase with broad substrate specificity. Demonstration of in vitro substrate conversion catalyzed by reprogrammed and purified MCPs challenge the view of MCPs as substrate-specific, tight metabolic insulators. Therefore, spatial orthogonality by scaffolding of enzymes into microreactors appears to be the natural function of MCPs.  Above all, our findings open the door to a broad range of in vitro and in vivo MCP-applications in (nano)biotechnology.

(1) Mampel, J et al., 2013. Trends Biotechnology (31), 52-60

(2) Shively, JM et. al., 2009. Encyclopedia of Microbiology, 404-424