Whole cell adhesion strength of morphotypes and isolates of Phaeodactylum tricornutum (Bacillariophyceae)

Cell adhesion molecules (CAMs) are important in prokaryotes and eukaryotes for cell-cell and cell-substratum interactions. The characteristics of adhesive proteins in the model diatom Phaeodactylum tricornutum were investigated by bioinformatic analysis and in vivo characterization. Bioinformatic analysis of the protein coding potential of the P. tricornutum genome used an amino-acid profile that we developed as a new system to identify uncharacterized or novel CAMs. Putative diatom CAMs were identified and seven were characterized in vivo, by generation of transgenic diatom lines overexpressing genes encoding C-terminal yellow fluorescent protein (YFP) fusion proteins. Three of these selected genes encode proteins with weak similarity to characterized proteins, a c-type lectin and two fasciclins, whereas the others are novel. The resultant cell lines were investigated for alterations in their adhesive ability. Whole cell-substratum adhesion strength was measured in a fully turbulent flow chamber, while atomic force microscopy was used to quantify the relative frequency of adhesion, as well as the length and strength of single molecules in the secreted mucilage. Finally, quartz crystal microbalance analysis characterized the visco-elastic properties and interaction of the mucilage-substratum interface. These combined studies revealed a range of phenotypes affecting adhesion, and led to the identification of candidate proteins involved in diatom adhesion. In summary, our study has for the first time combined bioinformatics and molecular physiological studies to provide new insights into diatom adhesive molecules.

Section: Methodssupporting

confidence: 82%

“…This percentage removal rate corresponds to the percentage removed found previously for P . tricornutum (strain 1 8.6) (Stanley and Callow ).…”

Section: Methodsmentioning

confidence: 99%

Adhesion molecules from the diatom Phaeodactylum tricornutum (Bacillariophyceae): genomic identification by amino‐acid profiling and in vivo analysis

Willis

Eason-Hubbard

Hodson

et al. 2014

“…Cultures of the ovoid and fusiform morphotypes both secrete mucilage containing carbohydrates, proteins and sulfates (Ford and Percival ). In this study, microscopy showed that the two morphotypes secreted EPS into the surrounding environment, although only the ovoid morphotype adheres to the substratum (Stanley and Callow ) and is motile (Iwasa and Shimizu ). The mucilage secreted by the ovoid form enveloped the cells and then accumulated upon the substratum surface.…”

Section: Discussionmentioning

confidence: 71%

“…The triradiate and fusiform morphotypes are planktonic while the ovoid form is adhesive, motile, and benthic. The ovoid form has a single silica valve that is embedded in the organic cell wall and contains a raphe (Wilson 1946, Lewin et al 1958, Iwasa and Shimizu 1972, Borowitzka and Volcani 1978, Stanley and Callow 2007. The three morphotypes are interchangeable within the same strain and culture and changes are thought to be triggered by environmental conditions (Wilson 1946, Marsot and Houle 1989, De Martino et al 2007, 2011.…”

mentioning

confidence: 99%

Characterization of the extracellular matrix of Phaeodactylum tricornutum (Bacillariophyceae): structure, composition, and adhesive characteristics

Willis

Chiovitti

Dugdale

et al. 2013

The extracellular matrix of the ovoid and fusiform morphotypes of Phaeodactylum tricornutum (Bohlin) was characterized in detail. The structural and nanophysical properties were analyzed by microscopy. Of the two morphotypes, only the ovoid form secretes adhesive mucilage; light microscopy and scanning electron microscopy images showed that the mucilage was secreted from the girdle band region of the cell as cell-substratum tethers, accumulating on the surface forming a biofilm. After 7 d, the secreted mucilage became entangled, forming adhesive strands that crisscrossed the substratum surface. In the initial secreted mucilage atomic force microscopy identified a high proportion of adhesive molecules without regular retraction curves and some modular-like adhesive molecules, in the 7 d old biofilm, the adhesive molecules were longer with fewer adhesive events but greater adhesive strength. Chemical characterization was carried out on extracted proteins and polysaccharides. Differences in protein composition, monosaccharide composition, and linkage analysis are discussed in relation to the composition of the frustule and secreted adhesive mucilage. Polysaccharide analysis showed a broad range of monosaccharides and linkages across all fractions with idiosyncratic enrichment of particular monosaccharides and linkages in each fraction. 3-linked Mannan was highly enriched in the cell frustule fractions indicating a major structural role, while Rhamnose and Fucose derivatives were enriched in the secreted fractions of the ovoid morphotype suggesting involvement in cell adhesion. Comparison of SDS-PAGE of extracellular proteins showed two major bands for the ovoid morphotype and four for the fusiform morphotype of which only one appeared to be common to both morphotypes.

“…These coatings do not prevent colonization by fouling organisms but are designed as “fouling‐release” coatings; that is, they “release” adhered organisms by the hydrodynamic forces generated when a ship moves through the water. Paradoxically, and in contrast to macroalgae, such as Ulva , diatoms adhere more strongly to these hydrophobic coatings and, conversely, adhere more weakly to hydrophilic surfaces such as glass (Holland et al 2004, Statz et al 2006, Cassé et al 2007, Stanley and Callow 2007). Similar trends in adhesion were noted in comparisons between surfaces formed from hydrophobic fluorinated, and hydrophilic, PEGylated block copolymers (Krishnan et al 2006).…”

mentioning

confidence: 99%

THE ROLE OF NITRIC OXIDE IN DIATOM ADHESION IN RELATION TO SUBSTRATUM PROPERTIES¹

Thompson

Taylor

Brownlee

et al. 2008

Self Cite

Adhesion of raphid diatoms to surfaces, mediated by the secretion of extracellular polymeric substances (EPS), is an important strategy for growth and survival. Diatom biofilms are also important in the context of biofouling. Diatoms exhibit selectivity in adhering to surfaces, but little is understood about how they perceive the properties of a substratum and translate that perception into altered adhesion properties. In this study, we demonstrate that Seminavis robusta Danielidis et D. G. Mann, like many other pennate diatoms, adheres more strongly to hydrophobic surfaces (such as silicone elastomer foul-release coatings) than to hydrophilic surfaces. To explore the cellular mechanisms that may underlie this selectivity, we tested the hypothesis that diatoms may perceive a hydrophilic surface as unconducive to adhesion through a form of stress response involving nitric oxide (NO) production. Single-cell imaging with the fluorescent indicator DAF-FM DA (4-amino-5-methylamino-2',7'-difluorofluorescein diacetate), revealed NO levels that were 4-fold higher in cells adhered to a hydrophilic surface (acid-washed glass) compared with a hydrophobic surface (polydimethylsiloxane elastomer, PDMSE). Elevated levels of NO caused by the addition of the NO donor S-nitroso-N-acetylpenicillamine (SNAP) did not affect growth, but cells showed reduced adhesion strength to both glass and PDMSE. Addition of the nitric oxide synthase inhibitor NG-monomethyl-l-arginine (NMMA) caused a small but significant increase in adhesion strength. Overall, the results suggest that NO acts as a signal of the wettability properties of substrata for Seminavis.