engleski

Are marine polysaccharide gels harvesting silica?

Diatoms are single cellular algae which are considered the most successful and widespread groups of photosynthetic eukaryotes contributing up to ~25% of the global primary production [1]. For growth they require Si, in the form of silicic acid, to build their beautiful, ornamented silica- based cell walls. As Si is often depleted in marine environment, particularly in surface waters, it is frequently a limiting factor for their growth. Recently we found that marine polysaccharides assembled in gel network accumulate SiO2 nanoparticles [2]. Here we examine the role of such assemblies in harvesting silica from seawater. We studied several bio-relevant systems: (i) diatom EPS and biofilm, (ii) marine gel networks and (iii) model polysaccharides systems, exposed to SiO2 NPs or in the presence of orthosilicate ions using AFM as a main tool. In all accounts, marine biopolymers display a strong interaction with Si. In the case of SiO2 NPs, the incorporation of individual NPs into the gel network was identified. On the other hand, in the presence of orthosilicate ions, nucleation and growth of primary silica NPs was revealed. These interactions could have significant environmental implications. By harvesting Si, marine gels provide Si-replete microhabitats for diatoms and therefore can directly influence their distribution, abundance and growth leading also to major impacts on silicon and carbon cycles [3]. From the biotechnological point of view, such interaction of NPs and orthosilicate ions with marine polysaccharides can be applied for the design of composite materials, such as biocompatible hybrid gels with new properties.

marine polysaccharides; biopolymers; diatom; silica

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