Algal Cell Walls

Abstract

Algae represent a diverse group of mostly photosynthetic eukaryotes that are profoundly important to Earth's ecosystems and human economy. These organisms possess a variety of extracellular matrix (ECM) components that are critical for multiple life functions. The most well‐studied ECMs are cell walls that are common to the green algae, red algae and brown algae. The typical cell wall consists of crystalline fibrillar polysaccharides (e.g. cellulose) that interact with a surrounding matrix of polysaccharides and proteoglycans. The matrix polysaccharides may be sulfated or acidic and some can complex various cations to form hard surfaces. Other distinct cell wall‐like coverings are found in algae including glycoprotein walls of volvocalean flagellates and silica‐complexed frustules of diatoms. Other noncell wall ECM types of algae include the amphiesma or dinoflagellates and the coccosphere of haptophytes. Key Concepts Algae possess a variety of extracellular matrices including cell walls. Most green, red and brown algae have cell walls consisting of a composite of a fibrillar polysaccharide framework associated with a polysaccharide/protein matrix. Unique cell walls are found in some algal groups including crystalline glycoprotein cell walls of volvocalean green algae and silica‐complexed cells walls of diatoms. Many algae do not have cell walls but have coverings made of complex scales and plates. The cell wall is synthesised and deposited externally through the coordinated action of the endomembrane and cytoskeletal systems.

Search for evolutionary roots of land plant arabinogalactan‐proteins in charophytes: presence of a rhamnogalactan‐protein in Spirogyra pratensis (Zygnematophyceae)

“…Monoclonal antibodies directed against AG-epitopes are tools for the microscopic detection of AGPs in algae. In CGA, AG-epitopes were detected by JIM8 and JIM13 in Chara ( Domozych et al, 2009 ), by JIM8, JIM13 and JIM14 in Micrasterias ( Eder et al, 2008 ; Lütz-Meindl and Brosch-Salomon, 2000 ; Sørensen et al, 2011 ), by JIM13 in Mougeotia and Spirogyra ( Permann et al, 2021a , b ), and by JIM8 and JIM13 in Chlorokybus , Coleochate , Penium , Zygnema and Spirogyra ( Domozych, 2019 ; Palacio-López et al, 2019 ). JIM8 is recognizing an epitope containing 1,6-linked Gal ( Ruprecht et al, 2017 ), but our results on Nitellopsis have shown that this epitope is present, although AGPs are missing.…”

Fucoid brown algae inject fucoidan carbon into the ocean

“…Brown algae mainly synthesize the polysaccharides laminarin, cellulose, alginate, and fucoidan: laminarin and cellulose from the immediate photosynthesis product glucose, alginate from uronic acids, and fucoidan from fucose. Fucoidan can be decorated with additional monosaccharides, as well as acetyl and sulfate groups giving fucoidan a net negative charge ( 20 – 22 ). While laminarin stores energy within cells ( 21 ), cellulose and alginate fulfill structural functions as cell wall constituents ( 20 ).…”

Microbial communities mediating algal detritus turnover under anaerobic conditions

“…The reason for this observed pattern of Clostridiales genera/families selection on kelp could only be speculated upon. A possible contributing factor could be the unique cell wall structure of kelp (or brown algae); multiple cellulose microfibrils layers embedded in large interfibrillar matrices that are mostly composed of alginates and fucans (Domozych, 2001; Youssef et al, 2015). Alginate (Preiss & Ashwell, 1962a; Preiss & Ashwell, 1962b) and fucans (Descamps et al, 2006; Kusaykin et al, 2016) degradation requires highly specific enzymes machineries.…”

“…2–5, Table 3). While Chlorella and Chara cell walls are quite distinct, they are both similar in being rich in fibrous cellulose and/or hemicellulose with amorphous middle layers composed mainly of pectin (homogalacturonic and rhamnogalacturonic acids polymers) in Charophyta , or sulfated polysaccharides in Chlorophyceae (Domozych, 2001; Domozych et al, 2014; Youssef et al, 2015). We reason that the relative similarity of the communities enriched on both types of algae, as well as the enrichment for multiple, rather than a single group of microbial lineages (VadinBC27, Spirochaeta , Lachnospiraceae , Buttauxiella , and Pantoea ) is a reflection of the relative ubiquity of microbial lineages capable of the anaerobic degradation of cellulose, hemicellulose, and pectin in the algal cell walls, hence allowing ready access to the intracellular substrates within the algal cells.…”