Population-level heterogeneity complicates utilization of Synechococcus elongatus PCC 7942 surface display platforms

Area of Science:

• Microbiology
• Synthetic Biology
• Biotechnology

Background:

• Surface display systems are crucial for microbial applications but are underdeveloped in photosynthetic organisms like cyanobacteria.
• Cyanobacteria offer unique advantages for biotechnology due to their photosynthetic capabilities.

Purpose of the Study:

• To engineer surface display systems in *Synechococcus elongatus* PCC 7942, a model cyanobacterium.
• To enable cyanobacteria to interact with other biological and non-biological targets via surface-displayed molecules.

Main Methods:

• Modification of outer-membrane proteins SomA and Intimin to display tags, such as SpyTag.
• Introduction of engineered constructs into *Synechococcus elongatus* PCC 7942.
• Assessment of protein translocation, tag accessibility, and ligand binding on the cyanobacterial cell surface.

Main Results:

• Re-engineered SomA constructs were successfully translocated to the cyanobacterial cell surface.
• The displayed tags could bind to compatible ligands, demonstrating potential for targeted interactions.
• Heterogeneity in tag accessibility on living cells limited the overall attachment efficiency and penetrance of the displayed molecules.

Conclusions:

• Surface display in cyanobacteria is feasible using modified outer-membrane proteins like SomA.
• Challenges remain in achieving uniform tag accessibility for robust surface display applications in photosynthetic microbes.
• Further optimization is needed to overcome cell surface heterogeneity for effective cyanobacterial surface display systems.