Bacterial Extracellular Polysaccharides in Biofilm Formation and Function

Abstract

Microbes produce a biofilm matrix consisting of proteins, extracellular DNA, and polysaccharides that is integral in the formation of bacterial communities. Historical studies of polysaccharides revealed that their overproduction often alters the colony morphology and can be diagnostic in identifying certain species. The polysaccharide component of the matrix can provide many diverse benefits to the cells in the biofilm, including adhesion, protection, and structure. Aggregative polysaccharides act as molecular glue, allowing the bacterial cells to adhere to each other as well as surfaces. Adhesion facilitates the colonization of both biotic and abiotic surfaces by allowing the bacteria to resist physical stresses imposed by fluid movement that could separate the cells from a nutrient source. Polysaccharides can also provide protection from a wide range of stresses, such as desiccation, immune effectors, and predators such as phagocytic cells and amoebae. Finally, polysaccharides can provide structure to biofilms, allowing stratification of the bacterial community and establishing gradients of nutrients and waste products. This can be advantageous for the bacteria by establishing a heterogeneous population that is prepared to endure stresses created by the rapidly changing environments that many bacteria encounter. The diverse range of polysaccharide structures, properties, and roles highlight the importance of this matrix constituent to the successful adaptation of bacteria to nearly every niche. Here, we present an overview of the current knowledge regarding the diversity and benefits that polysaccharide production provides to bacterial communities within biofilms.

Bispecific antibody targets multiple Pseudomonas aeruginosa evasion mechanisms in the lung vasculature

“…In fact, these are one of the key phagocytic cells in the lung capillaries (23). We observed by flow cytometry that 5%-15% of CD45-positive cells in the lungs are neutrophils at steady state phage and neutrophil recognition of the bacteria (15,16). Indeed, P. aeruginosa Psl prevented phagocytosis and oxidant production in neutrophils (16).…”

“…The T3S injectisome has been shown to aid P. aeruginosa colonization of the host in a variety of ways, including systemic spread of the pathogen and the sequestration of P. aeruginosa in nonacidic vacuoles in corneal epithelial cells (12)(13)(14). Psl exopolysaccharide, on the other hand, is a serotype-independent and abundantly expressed extracellular sugar polymer implicated in P. aeruginosa biofilm formation (15). Psl has been implicated in preventing complement deposition, which would prevent macroPseudomonas aeruginosa is a major cause of severe infections that lead to bacteremia and high patient mortality.…”

Glycoside Hydrolases Degrade Polymicrobial Bacterial Biofilms in Wounds

“…The polysaccharide composition of multiple, biofilm-producing bacterial pathogens has been elucidated (18)(19)(20). One glycosidic linkage commonly seen within the exopolysaccharides secreted by a wide range of pathogens is the ␤-1,4 bond, such as that present in cellulose, an exopolysaccharide produced by many strains of Escherichia coli, Salmonella, Citrobacter, Enterobacter, Pseudomonas, and other bacteria (21).…”

Biofilm: An Important Bacterial Feature Still to Deal With

“…Garnett and Matthews [39]. Interestingly, a bacterial biofilm may present one or several bacterial species, which is only a small part of this matrix [40]. These bacteria survive under the biofilm sub-optimal ambient conditions exhibiting antibiotic resistance, leading to persistent infections [41].…”