Strategies to display heterologous proteins on the cell surface of Lactic Acid Bacteria using as anchor the C-terminal domain of Lactobacillus acidophilus SlpA

PALUMBO, MIRANDA CLARA; RUZAL SANDRA M.; GORDILLO, TANIA; FERNANDEZ DO PORTO DARIO; ALLIEVI, MARIANA CLAUDIA; PALOMINO, MARÍA MERCEDES

WORLD JOURNAL OF MICROBIOLOGY & BIOTECHNOLOGY

SPRINGER

Año: 2020 vol. 36

0959-3993

The surface layer (S-layer) protein of Lactobacillus acidophilus is a crystalline array of self-assembling subunits, non-covalently bound to the most outer cell wall envelope and constitutes up to 20% of the total cell protein content. These attributes make S-layer proteins an excellent anchor for the development of microbial cell-surface display systems. In Lactobacillus acidophilus the S-layer is formed predominantly by the protein SlpA. In a previous work we have shown that the C-terminal domain of SlpA is responsible for the cell wall anchorage on Lactobacillus acidophilus ATCC 4356. In the present report, we evaluated the C-terminal domain of SlpA of Lactobacillus acidophilus ATCC 4356 as a potential anchor domain to expose functional proteins on the surface of non-genetically modified lactic acid bacteria (LAB). To illustrate this point GFP-CTSlpA was firstly produced in Escherichia coli and the recombinant proteins were able to spontaneously associate to the cell wall of LAB in a binding assay. GFP was successfully displayed on the S-layer stripped surface of L. acidophilus. Both binding stability and cell survival of L. acidophilus decorated with the recombinant protein were studied in simulated gastrointestinal conditions. Furthermore, NaCl was tested as a safer alternative to LiCl for S-layer removal. This study presents the development of a protein delivery platform involving the GRAS microorganism Lactobacillus acidophilus which utilizes the contiguous, non-covalently attached S-layer at the cell surface of the bacteria and without introducing any genetic modification to L. acidophilus.