THE COMPLEX POLYSACCHARIDES OF THE RAPHID DIATOM PINNULARIA VIRIDIS (BACILLARIOPHYCEAE)¹

Abstract

A combination of carbohydrate analysis and atomic force microscopy (AFM) was used to characterize the polysaccharides of the pennate diatom, Pinnularia viridis (Nitzsch) Ehrenberg. Polymeric substances were fractionated into those in the spent culture medium (SCM) and those sequentially extracted from the cells with water at 45° C (WW), NaHCO3 containing EDTA at 95° C (HB), and 1 M NaOH containing NaBH4 at 95° C. Carbohydrate, protein, and sulfate were detected in all the fractions, but their relative proportions differed significantly. Nineteen sugars were identified, including pentoses, hexoses, 6‐deoxyhexoses, O‐methylated sugars, aminohexoses, and traces of uronic acids. To some extent, the same constituent monosaccharides and a proportion of the linkage patterns occurred in all four fractions, indicating the fractions contained a spectrum of highly heterogeneous but structurally related polysaccharides. Several carbohydrates were enriched in specific fractions. A soluble, partially substituted, 3‐linked galactan was slightly enriched in the SCM. The WW fraction was highly enriched in 3‐linked glucan, presumably derived from chrysolaminaran. Chemical and AFM data for the WW and HB fractions indicated that compositional differences were associated with substantial changes in the morphology and properties of the cell surface mucilage. Soluble polymers relatively enriched in fucose conferred a degree of softness and compressibility to the mucilage, whereas most of the mucilage comprised firmer more gelatinous polymers comparatively enriched in rhamnose. The frustule residue dissolved during extraction with NaOH, and a partially substituted 3‐linked mannan, together with relatively large amounts of protein, was obtained.

The glucans extracted with warm water from diatoms are mainly derived from intracellular chrysolaminaran and not extracellular polysaccharides

“…The structure of the glucan was not elucidated, but proposed that the putative extracellular glucan served as an energy-reserve carbohydrate, possibly under the same control as chrysolaminaran. In a study of the total polysaccharides from a freshwater benthic diatom, Pinnularia viridis (Chiovitti et al, 2003), 1,3-linked glucans were found to be the dominant component of the extract obtained by treatment of thawed cells with water at 458C. Atomic force microscopy showed that the topography and properties of the cell surface mucilage of the diatom had been altered during warm-water extraction.…”

“…willei), Chaetoceros sp., Skeletonema costatum and Stauroneis amphioxys (Ford & Percival, 1965;Handa & Yanagi, 1969;Myklestad & Haug, 1972;Smestad Paulsen & Myklestad, 1978;McConville et al, 1986). More recently, linkage analyses of water extracts obtained during sequential extraction of Achnanthes longipes (Wustman et al, 1997) and Pinnularia viridis (Chiovitti et al, 2003) yielded 1,3-linked glucopyranose (Glcp) as the dominant component.…”

“…Although diatom extracellular polysaccharides are unique compared with those of other algae and land plants, their structures are poorly understood and generalizations are difficult. They are usually heterogeneous, comprising hexoses, pentoses, 6-deoxyhexoses, Nacetylaminosugars, and/or O-methylated sugars, and acidic, with uronic acids and/or sulphate esters (for review see Hoagland et al, 1993;Wustman et al, 1997Wustman et al, , 1998McConville et al, 1999;Chiovitti et al, 2003).…”

Progress of marine biofouling and antifouling technologies

“…Many types of enzymes, such as oxidoreductases, transferases, hydrolase, lyase, isomerase, and ligase, have been reported to have antifouling capabilities [25,58,[97][98][99][100][101][102][103][104][105][106]. From the perspective of enzymatic antifouling technology, biofouling problems are caused by the formation and reproduction of biofilms, and the adhesion of spores and larvae of macroorganisms.…”

“…Generally, polysaccharide degradation is executed by glycosylase. However, to degrade polysaccharides is difficult because the process is quite complex [106] and glycosylase can target only a limited range of linkages. Consequently, it would be difficult to choose an appropriate glycosylase for broadspectrum antifouling [103].…”