A Marine Photosynthetic Microbial Cell Factory as a Platform for Spider Silk Production

Spider dragline silk protein, major ampullate spidroin (MaSp) are mainly composed of multiple types of MaSp, such as MaSp1 and MaSp2. MaSp has a conserved primary structure comprising three domains: a repetitive central domain and nonrepetitive N-terminal and C-terminal domains. The MaSp repetitive domains are arranged in alternating blocks of polyalanine (crystalline) and glycine-rich (amorphous) sequences, which are responsible for the high tensile strength and high elasticity, respectively, of spider silk fibers. Recombinant spidroins have been successfully expressed in various hosts such as bacteria, yeasts, insects, plants, and animals. However, it is still a great challenge to produce spidroins on a large scale with a sustainable production process. In this study, we develop an economical and sustainable marine photosynthetic microbial cell factory using Rhodovulum sulfidophilum, which is a marine purple nonsulfur bacterium that is capable of producing the hydrophobic repetitive sequence of MaSp1 (1-mer, 2-mer, 3-mer and 6-mer from Nephila clavipes) using small amount of organic substance under photoheterotrophic or photoautotrophic growth conditions.