Biology Department Seminar

Metabolic engineering of soil bacteria (for example, Pseudomonas putida) for biosensing, biodegradation of environmental contaminants or for adding value to industrial waste has been based since the mid-80's in the introduction of new genes that determine catalytic abilities and / or improving their expression. This approach is being challenged by Systems Biology, in particular its emphasis on the interdependence between all cellular functions and the evidence that the existing networks of multi-protein interactions hinder the stable implantation of new components. In this context, we have developed two strategies for genetic refactoring of the catalytic abilities of P. putida based on the isolation (orthogonalization) and subsequent re-connection of metabolic modules present in the microorganism. In one case, orthogonalization of a given module is brought about by the conditional proteolysis of the enzymes that act as connectors to the rest of metabolism. The second strategy involves expression of intracellular nanobodies that block the activity of desired enzymes in vivo. These tools have enabled us to generate strains that either overproduce the valuable glycolytic intermediary di-hydroxyacetone phosphate (DHAP), accumulate 2,5-di-hydroxypirydine from nicotinic acid or inhibit selectively the BphC activity. The modularization and reconnection of metabolic blocks allows the expansion of the catalytic capabilities of these bacteria by playing with the connectivity of the network instead of changing the nature of its components. Finally, bacteria designed for release require adoption of genetic tools different from those used for model Laboratory bacteria, as long as the aim is the generation of robust -yet safe- microorganisms. In this context the use of the Tn5 and Tn7 transposition systems for bacteria usable in a diversity of applications in the field will be discussed also.