The Surface Layer Protein of the Bacillus sphaericus Isolate JG A-12 from a Uranium Waste Pile

Many bacteria possess a crystalline protein or glycoprotein surface layer (S-layer) as the outermost component of their cell wall. The interest in bacterial S-layers increased in the last time. This protein might be applied as biomolecular template for making nanostructures, e.g. for the development of biosensors. The surface layer of a natural Bacillus sphaericus isolate JG A-12, recovered from a uranium waste pile, was analyzed and compared to the surface layer
of a reference strain (Bacillus sphaericus NCTC 9602). The molecular weights of the S-layer proteins of both, the reference strain NCTC 9602 and the strain JG A-12, were examined with a denaturating polyacrylamid gel electrophoresis and were estimated to be approximately 135 kDa. In addition to that, the first 20 amino acids at the N-termini of the 135 kDa proteins of the strains 9602 and JG A-12 were identical. However, no similarity to the S-layer proteins of
the Bacillus sphaericus strains 2362 and P-1 was found. Interestingly, in the case of the uranium waste isolate, in addition to the S-layer protein a second, smaller protein with a size of 30 kDa was copurified. The amino acid sequence of the N-terminus of the 30 kDa protein was significantly different from those of the S-layer proteins. This small protein possesses a similarity to many flagellins of different bacteria. The S-layer of the reference strain Bacillus
sphaericus NCTC 9602 and of the uranium waste isolate JG A-12 were also characterized using transmission electron microscopy after negative staining. Both S-layers have a p4 symmetry with lattice constants of 12,9 nm (S-layer of Bacillus sphaericus NCTC 9602) and 12,5 nm (S-layer of JG A-12). It seems, that the reference strain Bacillus sphaericus NCTC 9602 and the isolate JG A-12 possess the S-layer protein with same structure.