Secretion mechanism and adhesive mechanism of diatoms: Direct evidence from the quantitative analysis

Diatoms are one of the biofouling species attached to the substrate that can cause substrate corrosion, fuel consumption and destruction of the ecological balance. Therefore, the study of single-cellfouling organisms, particularly, the quantitative analysis of extracellular polymeric substances (EPS) is essential for antifouling. Atomic Force Microscope (AFM) was used to quantify three types of diatoms: Nitzschia closterium (N. closterium), Phaeodactylum tricornutum (P. tricornutum) and Halamphora sp. The situation of N. closterium was analyzed multiple times and the results showed that the adhesion value range of N. closterium with nacked chromatophores was three times larger than the mature one. The discovery of the EPS secretion from chromatophore is discussed in this paper, and the proposed mechanism has special implications to study the adhesive protein. Adhesion capabilities of different diatom genera and species were revealed as well. The average adhesion values of N. closterium, P. tricornutum and Halamphora sp. were about 1.7 nN, 3.3 nN and 2.5 nN, respectively, which suggest P. tricornutum could be a better candidate for testing diatom resistance on epoxy materials in the lab. Experimental data and discussions in this paper provide insights for further study of diatoms in the field of antifouling.