Intercellular adhesion promotes clonal mixing in growing bacterial populations

Dense bacterial communities, known as biofilms, can have functional spatial organization driven by self-organizing chemical and physical interactions between cells, and their environment. In this work, we investigated intercellular adhesion, a pervasive property of bacteria in biofilms, to identify effects on the internal structure of bacterial colonies. We expressed the self-recognizing ag43 adhesin protein in Escherichia coli to generate adhesion between cells, which caused aggregation in liquid culture and altered microcolony morphology on solid media. We combined the adhesive phenotype with an artificial colony patterning system based on plasmid segregation, which marked clonal lineage domains in colonies grown from single cells. Engineered E. coli were grown to colonies containing domains with varying adhesive properties, and investigated with microscopy, image processing and computational modelling techniques. We found that intercellular adhesion elongated the fractal-like boundary between cell lineages only when both domains within the colony were adhesive, by increasing the rotational motion during colony growth. Our work demonstrates that adhesive intercellular interactions can have significant effects on the spatial organization of bacterial populations, which can be exploited for biofilm engineering. Furthermore, our approach provides a robust platform to study the influence of intercellular interactions on spatial structure in bacterial populations.For this research, A.K. and T.J.R. were supported by the EC FP7project no. 612146 (PLASWIRES) awarded to J.P.H., A.K. has also been supported by a BBSRC CASE studentship in partnership with Microsoft Research, F.F. was supported by the UK Biotechnological and Biological Sciences Research Council (BBSRC) Synthetic Biology Research Centre ‘OpenPlant’ award (BB/L014130/1), CONICYT-PAI/Concurso Nacional de Apoyo al Retorno de Investigadores/as desde el Extranjero Folio 182130027, Fondo de Desarrollo de Areas Prioritarias (FONDAP) Center for Genome Regulation 1(15090007), Millennium Nucleus Center for Plant Systems and Synthetic Biology 1(NC130030) and Fondecyt Iniciación 111140776. T.J.R. has also been supported by Fondecyt Iniciación 11161046