Antigen expression in biofilm cells of Aeromonas hydrophila employed in oral vaccination of fish.

Total protein, S-layer protein and lipopolysaccharides (LPS) of biofilm cells of Aeromonas hydrophila were analysed by SDS-PAGE and compared with that of planktonic cells. In the whole cell lysate of biofilm cells, about 15 proteins were repressed while three new proteins were expressed compared to that in planktonic cells. Interestingly, in biofilm cells the S-layer proteins were lost and LPS showed an additional high molecular weight band compared to that in planktonic cells. We propose that the change in LPS profile must have contributed to the loss of S-layer. Also, the high molecular weight band of LPS might play a role in the better performance of biofilm oral vaccine by eliciting a protective immune response.