Holographic microscopy provides new insights into the settlement of zoospores of the green alga Ulva linza on cationic oligopeptide surfaces

Abstract

Interaction of zoospores of Ulva linza with cationic, arginine-rich oligopeptide self-assembled monolayers (SAMs) is characterized by rapid settlement. Some spores settle (ie permanently attach) in a ‘normal’ manner involving the secretion of a permanent adhesive, retraction of the flagella and cell wall formation, whilst others undergo ‘pseudosettlement’ whereby motile spores are trapped (attached) on the SAM surface without undergoing the normal metamorphosis into a settled spore. Holographic microscopy was used to record videos of swimming zoospores in the vicinity of surfaces with different cationic oligopeptide concentrations to provide time-resolved insights into processes associated with attachment of spores. The data reveal that spore attachment rate increases with increasing cationic peptide content. Accordingly, the decrease in swimming activity in the volume of seawater above the surface accelerated with increasing surface charge. Three-dimensional trajectories of individual swimming spores showed a ‘hit and stick’ motion pattern, exclusively observed for the arginine-rich peptide SAMs, whereby spores were immediately trapped upon contact with the surface.

Keywords:

• holographic microscopy
• cationic peptides
• zoospores
• Ulva linza
• tracking
• 3-dimensional motility

Conflict of interest disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental material

The supplemental material for this paper is available online at http://dx.doi.org/10.1080/08927014.2015.1022534

Additional information

Funding

This work was funded by the US Office of Naval Research [awards N000141210498 (MG & AR); and N0001-08-1-0010 (JAC & MEC)], the 6th framework EU project AMBIO, and the DFG Project [RO 2524/2-2].