Genetic regulation, biosynthesis and applications of extracellular polysaccharides of the biofilm matrix of bacteria.

Bacterial biofilm formation is dependent mainly on the decision-making process of the two key factors of the gene regulatory network, namely the Quorum Sensing (QS) system and bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). c-di-GMP is a secondary messenger molecule that enhances extracellular polysaccharides production by activating pelD and alg44. Genes involved in the metabolic pathway for the biosynthesis of extracellular polysaccharides are clustered within the genome of the producing bacteria. The extracellular polysaccharide gene cluster encodes specific regulatory enzymes and transporter proteins involved in the different steps of the biosynthesis route. The diversity of extracellular polysaccharides produced by the bacteria is synthesized via different biosynthesis pathways. Understanding the genetic regulation and biosynthesis of extracellular polysaccharides is crucial for tailor-made polymers via genetic, metabolic, and protein engineering approaches. This review illustrates structure, structure-function relationship, genetics, regulation, biosynthetic pathways, and various applications of extracellular polysaccharides.