Basket scales of the green alga, Mesostigma viride: Chemistry and ultrastructure

Abstract

The unicellular green algal flagellate, Mesostigma viride, possesses an extracellular matrix consisting of three layers of highly distinct scales. This study focused upon the elaborate basket scales. The basket scale is approximately 450–500 nm in height and consists of a solid base, two distinct lattices, two upper rims and various struts and roots. Pure preparations of isolated basket scales were obtained and used for subsequent chemical and immunological analyses. X-ray microanalyses revealed the scale as being mineralized with both calcium and phosphorus. Fourier Transform Infrared Spectroscopic analyses revealed the presence of phosphate, suggesting in turn that the basket scale is complexed with calcium phosphate. SDS-gel electrophoresis of partially digested scales revealed the presence of two protein components, a high Mr, non-migrating form and a form with a Mr of approximately 48000. Further biochemical analyses of scales showed the presence of two major sugars: glucose and the unusual keto sugar acid, 3-deoxy-lyxo-2-heptulosaric acid, or DHA. Antibodies to scales were raised in rats and used in immunolabeling studies. It is estimated from immunofluorescence studies that a cell of 8 μm contains about 800 basket scales. The scales are in a close-packed arrangement resulting in quasi-crystalline arrays upon the cell surface.