Cyanobacterial Surface Display System Mediates Engineered Interspecies and Abiotic Binding.

Cyanobacteria are uniquely suited for the development of sustainable bioproduction platforms but are currently underutilized in scaled applications in part due to a lack of genetic tools. Here, we develop a surface display system in the cyanobacterial model Synechococcus elongatus PCC7942 via expression of modified versions of the outer membrane porin SomA. Importantly, we demonstrate accessibility of heterologous functional groups on the recombinant porin to the external environment in living cells. We show that this requires the removal of occluding factors that include lipopolysaccharides and a putative surface layer protein. Displayed epitopes on SomA can be utilized to mediate physical adhesion between living cyanobacteria and abiotic surfaces or an engineered Saccharomyces cerevisiae partner strain. We show that >80% of cyanobacterial cells attach to functionalized magnetic beads, allowing for magnet-assisted recovery. This work showcases the development of a functional surface display system in cyanobacteria with wide-ranging applications.