Team:UPO-Sevilla

Project outline The possibility of specifically targeting bacteria to biological or abiotic surfaces is a promising technology of potential use in therapy, pest control and bioremediation, among others. However, since in most cases bacteria are not drawn towards their targets, the possibility of specific interaction is limited to those bacterial cells that randomly collide with the surface, thus requiring a high bacterial population to achieve efficient targeting. On the other hand, most bacteria are specifically attracted by gradients of a variety of chemicals, thus achieving high cell densities in the areas where the chemoattractants are present at higher concentration. The aim of this project is to explore the possibility of directing a relatively small population of bacteria to interact efficiently with a non-diffusible target exposed on a biotic or abiotic surface. To achieve this goal, our proposal involves the construction of bacterial strains harboring a two-tiered regulatory circuit involving the following elements: 1. A cell surface-signaling circuit based on the Prh system of Ralstonia solanacearum to detect surface-associated polysaccharides and activate gene expresion. The Prh system has the unique property of detecting a non-diffusible signal present in plant cell polysaccharides and transducing that signal across the outer membrane, the periplasm and the cell membrane to activate transcription by means of the alternative extracytoplasmic function sigma factor PrhI. 2. A gene expression system based on the PrhI-dependent promoter PprhJ engineered to activate the synthesis and excretion of a chemoatractant (CA) suitable for the host bacteria upon interaction with surface-exposed polysaccharides. The expected response is the accumulation of bacterial cells on the polysaccharide-loaded surface, as the initial attachment of a few cells will be amplified by the secondary chemotactic response triggered by the interaction with the surface (Figure 1).