Contribution of frustules and mucilage trails to the mobility of diatom Navicula sp.

Lei Chen,Ding Weng,Shan Cao,Jiadao Wang,Chuan Du

doi:10.1038/s41598-019-43663-z

Abstract

The secreted mucilage trails of the diatom Navicula sp. in the process of motility were studied by scanning electron microscopy (SEM), transmission electron microscope (TEM), atomic force microscopy (AFM) and Raman spectra etc. Contrary to previous studies, force measurement was taken directly on the mucilage trails of live cells using the method of in situ force mapping by AFM. The retraction force curve presented an increased tip-substrate peak and a small saw-tooth pattern tip-mucilage peak. Especially, same measurements on various substrates with different surface energy revealed that the mucilage trails actually functioned as a medium increasing the adhesive force between the diatom and substrates, which is crucial to diatom’s adhesion and locomotion. In addition, the mechanical properties of mucilage trails were quite different from mucilage strands in the maximum adhesive force and the maximum polymer extension length. Raman spectra indicated the difference in compositions that both of the two kinds of mucilages had proteins and polysaccharide, but the mucilage strands contained some other components with C=O, —CH2— and —CH3 asymmetric and symmetric stretches. This research hammers out more precise information about mucilage trails which would be useful in terms of diatom motility and biofouling prevention.

Highlights

Marine biofouling is a complex process that involves the adhesion, movement, growth and reproduction of marine organisms onto immersed artificial structures such as ship hulls, navigational instruments, aquaculture net cages and seawater intake pipes, causes problems such as increased drag, fuel consumption and instrument maintenance costs[1,2,3,4,5]
Diatom cells adhesion to different surfaces are assisted by the continual secretion of adhesive mucilage, a form of extracellular polymeric substance (EPS)[24,25,26,27,28,29]
It remains unclear whether the mucilage trails are formed from the same mucilage that can be found near the raphe, whether physicochemical changes occur in mucilage after shearing and separation from the cell, or whether cells can change the composition of mucilage during ‘gliding’

Summary

Introduction

Marine biofouling is a complex process that involves the adhesion, movement, growth and reproduction of marine organisms onto immersed artificial structures such as ship hulls, navigational instruments, aquaculture net cages and seawater intake pipes, causes problems such as increased drag, fuel consumption and instrument maintenance costs[1,2,3,4,5]. Previous research[30,31,34] has reported that it is preferable to utilize mucilage collected near the raphe to study mechanical properties, where the mucilage trails are thought to originate from, rather than trying to utilize the trails themselves. It remains unclear whether the mucilage trails are formed from the same mucilage that can be found near the raphe, whether physicochemical changes occur in mucilage after shearing and separation from the cell, or whether cells can change the composition of mucilage during ‘gliding’. Information on mucilage strands is still lacking and further investigation is essential to improve our understanding of diatom locomotion and biofouling

Methods

Results

Discussion

Conclusion