Antigen 43 from Escherichia coli induces inter- and intraspecies cell aggregation and changes in colony morphology of Pseudomonas fluorescens

Antigen 43 (Ag43) is a surface-displayed autotransporter protein of Escheri chia coli. By virtue of its self-association characteristics, this protein is able to mediate autoaggregation and flocculation off. coli cells in stat ic cultures. Additionally, surface display of Ag43 is associated with a dis tinct frizzy colony morphology in E. coli. Here we show that Ag43 can be ex pressed in a functional form on the surface of the environmentally importan t Pseudomonas fluorescens strain SBW25 with ensuing cell aggregation and fr izzy colony types. Using green fluorescence protein-tagged cells, we demons trate that Ag43 can be used as a tool to provide interspecies cell aggregat ion between E. coli and P. fluorescens. Furthermore, Ag43 expression enhanc es biofilm formation in P. fluorescens to glass surfaces. The versatility o f this protein was also reflected in Ag43 surface display in a variety of o ther gram-negative bacteria, Display of heterologous Ag43 in selected bacte ria might offer opportunities for rational design of multispecies consortia where the concerted action of several bacterial species is required, e.g., waste treatment and degradation of pollutants.