Algal Cell Walls

Abstract

Abstract Algal cell walls are composed of a diverse array of fibrillar, matrix and crystalline polymers interacting with various ions and water. The diverse array of cell walls exhibited in the various algal groups is a manifestation of ancient evolutionary origins and ecological pressures of modern earth habitats. Cell walls often represent the dominant component of the extracellular matrix and represent the largest or a significant percentage of the photosynthetically fixed carbon of the algae. Walls are typically fibrous composites of microfibrillar polysaccharides embedded in matrix polysaccharides and proteoglycans. Scales and extracellular polymeric substances may also constitute the algal extracellular matrix. The production of the cell walls requires the highly coordinated interaction of several subcellular systems and is controlled by complex gene expression programmes. Modern technologies employed from immunology, molecular genetics, biochemistry and microscopy‐based imaging are transforming our understanding of the cell structure, functions and development. Key Concepts: Algae represent a diverse group of photosynthetic eukaryotes with a wide range of cell wall types. New technologies derived from immunology, microscopy‐based imaging, molecular genetics and biochemistry are greatly enhancing our understanding of algal cell walls. Primitive green algae of the Prasinophyceae produce layers of multishaped scales. The Charophycean green algae produce cell walls containing polymers similar to land plants. The red algae possess complex composite cell walls made of cellulose, xylan or mannan fibrils and extensive matrix polysaccharides including the economically important carrageenan and agar. Diatoms produce highly sculpted frustules made of silica‐based composites and often produce extensive stalks and other extracellular polymeric substances. Brown algae produce cell walls containing cellulose, matrix polysaccharides and in some cases, phenolics.