Isolation and biochemical characterization of underwater adhesives from diatoms

Abstract

Many aquatic organisms are able to colonize surfaces through the secretion of underwater adhesives. Diatoms are unicellular algae that have the capability to colonize any natural and man-made submerged surfaces. There is great technological interest in both mimicking and preventing diatom adhesion, yet the biomolecules responsible have so far remained unidentified. A new method for the isolation of diatom adhesive material is described and its amino acid and carbohydrate composition determined. The adhesive materials from two model diatoms show differences in their amino acid and carbohydrate compositions, but also share characteristic features including a high content of uronic acids, the predominance of hydrophilic amino acid residues, and the presence of 3,4-dihydroxyproline, an extremely rare amino acid. Proteins containing dihydroxyphenylalanine, which mediate underwater adhesion of mussels, are absent. The data on the composition of diatom adhesives are consistent with an adhesion mechanism based on complex coacervation of polyelectrolyte-like biomolecules.

Keywords:

• Amphora coffeaeformis
• Craspedostauros australis
• diatom
• adhesive material
• 3
• 4-dihydroxyproline
• uronic acids

Acknowledgments

The authors would like to thank Dr M. Witt (Bruker Daltonik, Bremen, Germany) for FTMS measurements, J. Klemm and J. Steffen for expert technical assistance, Carson Meredith (Georgia Institute of Technology, Atlanta, GA, USA) for his suggestion to use the Waterpik device, and Carol Taylor (Louisiana State University, Baton Rouge, LA, USA) for kindly providing the dihydroxyproline standards.

Funding

This work was supported by the US Air Force Office of Scientific Research [grant number FA9550-12-1-0093] to NP and NK; Deutsche Forschungsgemeinschaft [grant number Br1278/12-3] to EB; the Max Planck Society to MH.