Alginates from Bacteria

Abstract

Introduction Historical Outline Chemical Structures Biosynthetic Pathway of the Alginate Precursor, GDP‐Mannuronic Acid Genetics of Alginate Biosynthesis Regulation of Alginate Biosynthesis Environmentally Induced Activation of alg Genes Genotypic Switch Polymerization and Export of the Alginate Chain Alginate‐Modifying Enzymes Mannuronan C‐5‐epimerases O‐Transacetylases Alginate Lyases The Role of Alginate in Biofilm Formation The Applied Potential of Bacterial Alginates Acknowledgments

In Vitro Alginate Polymerization and the Functional Role of Alg8 in Alginate Production by Pseudomonas aeruginosa

“…Many glycosyltransferases of the class II are involved not only in membrane translocation but also in polymerization itself (52,53). Thus, Alg8 might be the catalytic subunit of the alginate polymerase as previously suggested (45). This hypothesis was supported by the 20-fold overproduction of alginate by P. aeruginosa PDO300⌬alg8(pBBR1MCS-5:alg8) compared to P. aeruginosa PDO300, indicating that Alg8 is the bottleneck in alginate production (Table 3).…”

“…Alg8 is supposed to be a membrane protein that putatively encodes a glycosyltransferase linking the cytosolic precursor synthesis to polymer formation (45). Topological analyses of Alg8 using the SMART database (57) and the topology prediction tool TMHMM2 (37) suggested a signal sequence at the N terminus (1 to 32 amino acids) and four transmembrane helices (Fig.…”

“…The alginate biosynthesis pathway can be divided into four different stages: (i) synthesis of precursor substrate, (ii) polymerization and cytoplasmic membrane transfer, (iii) periplasmic modification, and (iv) export through the outer membrane. The precursor synthesis is well characterized and starts from the central metabolite fructose-6-phosphate, which is converted to GDP-mannuronic acid in four enzymatic steps by the proteins AlgA, AlgC, and AlgD (45). The modifications of the polymannuronate chain are carried out by a number of periplasmic proteins.…”

Expression of the psl Operon in Pseudomonas aeruginosa PAO1 Biofilms: PslA Performs an Essential Function in Biofilm Formation

“…The most characteristic feature of the mucoid phenotype is the secretion of large amounts of highly viscous exopolysaccharides. The copolymer alginate, which is composed of mannuronic acid and guluronic acid, appears to be the major component of the secreted polysaccharide (9,31), and besides nucleic acids and proteins, is the key factor in the development of mucoid biofilms which has been intensively studied (5,16,26,30). Biofilms generated by P. aeruginosa have been shown to enhance the resistant colonization of cystic fibrosis-diseased lungs and to confer several advantages to the respective microorganism, such as a high-level resistance to antibiotics and to the killing effect of leukocytes (1,18).…”

PslD Is a Secreted Protein Required for Biofilm Formation by Pseudomonas aeruginosa

“…An important virulence mechanism is the formation of a mucoid biofilm. Secreted alginate is a crucial constituent of the mucoid biofilm matrix (16,17). However, alginate-negative mutants of P. aeruginosa are also able to form nonmucoid biofilms, showing an architecture different from that of biofilms formed by alginate-overproducing mucoid P. aeruginosa (13,20).…”