Localization and Associative Strength of Acid Polysaccharides in Coccoliths of <i>Pleurochrysis haptonemofera</i> (Haptophyta) Predicted from Their Extractability from Partially Decalcified Coccoliths

Abstract

The coccolithophorids have calcified scales called coccoliths on their surface that include abundant acid polysaccharides. To determine the localization and associative strength of acid polysaccharides Ph-PS-1, -2, and -3 in coccoliths of Pleurochrysis haptonemofera, we analyzed the acid polysaccharides extracted with urea from partially decalcified coccoliths. On treatment of coccoliths with 8.0 M urea at pH 8.0 in boiling water, Ph-PS-2 was not extracted, but parts of Ph-PS-1 and -3 were from the surface without the crystal morphology being affected. When coccoliths were partially decalcified at various pHs (pH 8.0 -5.0), Ph-PS-1, -3, and -2 were extracted with urea in that order as the calcite crystals dissolved. Detection of the acid polysaccharides using fluorescein-isothiocyanate-labeled lectin (ConA) and anti-Ph-PS-2 antibodies demonstrated that Ph-PS-2 exists on the surfaces of both untreated and urea-treated coccoliths. Moreover, NaClO-treatment under moderate conditions extracted only Ph-PS-1, -3, and part of Ph-PS-2 from coccoliths, without separation of the crystal units, suggesting that at least some part of Ph-PS-2 acts as a glue connecting crystal units and/or a crystal unit and a base plate inside coccoliths. These results suggest that Ph-PS-2 exists not only on the surface but also inside of the coccoliths, most of it being strongly bound to coccoliths, while Ph-PS-1 and -3 are weakly associated close to the coccolith surface, in that order from the surface. This strongly supports a scheme in which PS-2 type acid polysaccharides play an important role in the crystal nucleation and PS-3 type functions during crystal growth.

Coccolithophore biomineralization: New questions, new answers

“…Moreover, the role of PS-3 was shown to be restricted to the later stages of crystal growth after the protocooccolith ring had been formed. This is consistent with later studies in the related species P. haptonemofera [19] showing that PS-1 and PS-3 were surface associated while PS-2 was associated with both the surface and interior of the coccolith, suggesting a role in crystal nucleation or maintenance of coccolith structure. The roles of other intra-crystalline organic components on the control of coccolith nucleation and growth remain to be elucidated.…”

Blueprints for the Next Generation of Bioinspired and Biomimetic Mineralised Composites for Bone Regeneration

“…The organic coating around the coccolithospheres, combined PS-1 and PS-3 polysaccharides, whereas PS-2 forms the organic baseplate template at the interface of calcite crystals. Less attention has been given to the role of PS-3, which is thought to function during the crystal growth phase of mineralisation [ 51 ]. In E. huxleyi , mineralisation is associated with polysaccharides in the labyrinthine system (reticular body) [ 10 ], whereas in P. carterae a large number of 20 nm particles, known as coccolithosomes [ 30 ], are found to agglomerate around the rim of the baseplate [ 26 , 49 ].…”

“…After mineralisation in P. carterae , a coating is formed through the dissociation of PS-1 and PS-3, both of which contain coccolithosomes [ 51 ]. These polysaccharides are reportedly composed of uronic acids and sulphate esters that are attached to a polymannose main chain [ 58 ].…”

Silicoflagellate double skeletons in the geologic record

“…Modern Dictyocha Ehrenberg and Stephanocha McCartney and Jordan (previously known as Distephanus Stöhr; see Jordan and McCartney, 2015) are held together by a zig-zag basal ring structure that projects pikes into the cellular domain of the paired skeleton (Moestrup and Thomsen, 1990), which is a possible adaptation to allow easy separation of the two skeletons after cellular division (McCartney et al, 2014c). Skeletons that lack pikes, such as the Marine Micropaleontology 117 (2015) [65][66][67][68][69][70][71][72][73][74][75][76][77][78][79] modern genus Octactis Schiller, do not show a zig-zag pattern in the basal ring and may be held together in a doublet by a strong organic adhesive (most likely of polysaccharide nature as seen in haptophytes and diatoms; e.g., Hirokawa et al, 2013 andWustman et al, 1997, respectively) at abbasal surfaces beneath the basal corners.…”