Hypothetical protein Avin_16040 as the S-layer protein of Azotobacter vinelandii and its involvement in plant root surface attachment

A proteomic analysis of a soil-dwelling, plant growth-promoting Azotobacter vinelandii strain showed the presence of a protein encoded by the hypothetical Avin_16040 gene when the bacterial cells were attached to the Oryza sativa root surface. An Avin_16040 deletion mutant demonstrated reduced cellular adherence to the root surface, surface hydrophobicity, and biofilm formation compared to those of the wild type. By atomic force microscopy (AFM) analysis of the cell surface topography, the deletion mutant displayed a cell surface architectural pattern that was different from that of the wild type. Escherichia coli transformed with the wild-type Avin_16040 gene displayed on its cell surface organized motifs which looked like the S-layer monomers of A. vinelandii. The recombinant E. coli also demonstrated enhanced adhesion to the root surface.