Role of exopolysaccharides in Pseudomonas aeruginosa biofilm formation and architecture
01 Aug 2011-Applied and Environmental Microbiology (American Society for Microbiology)-Vol. 77, Iss: 15, pp 5238-5246
TL;DR: It is demonstrated that the various exopolysaccharides and eDNA interactively contribute to the biofilm architecture of P. aeruginosa.
Abstract: Pseudomonas aeruginosa is an opportunistic human pathogen and has been established as a model organism to study bacterial biofilm formation. At least three exopolysaccharides (alginate, Psl, and Pel) contribute to the formation of biofilms in this organism. Here mutants deficient in the production of one or more of these polysaccharides were generated to investigate how these polymers interactively contribute to biofilm formation. Confocal laser scanning microscopy of biofilms formed in flow chambers showed that mutants deficient in alginate biosynthesis developed biofilms with a decreased proportion of viable cells than alginate-producing strains, indicating a role of alginate in viability of cells in biofilms. Alginate-deficient mutants showed enhanced extracellular DNA (eDNA)-containing surface structures impacting the biofilm architecture. PAO1 ΔpslA Δalg8 overproduced Pel, and eDNA showing meshwork-like structures presumably based on an interaction between both polymers were observed. The formation of characteristic mushroom-like structures required both Psl and alginate, whereas Pel appeared to play a role in biofilm cell density and/or the compactness of the biofilm. Mutants producing only alginate, i.e., mutants deficient in both Psl and Pel production, lost their ability to form biofilms. A lack of Psl enhanced the production of Pel, and the absence of Pel enhanced the production of alginate. The function of Psl in attachment was independent of alginate and Pel. A 30% decrease in Psl promoter activity in the alginate-overproducing MucA-negative mutant PDO300 suggested inverse regulation of both biosynthesis operons. Overall, this study demonstrated that the various exopolysaccharides and eDNA interactively contribute to the biofilm architecture of P. aeruginosa.
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TL;DR: The mechanism of antibiotic resistance in P. aeruginosa is a recently characterized mechanism, which includes biofilm-mediated resistance and formation of multidrug-tolerant persister cells, and is responsible for recalcitrance and relapse of infections.
908 citations
TL;DR: The central regulatory role of quorum sensing and signaling systems by nucleotide-based second messengers resulting in different lifestyles of P. aeruginosa is reviewed and various regulatory proteins will be discussed which form a plethora of controlling systems acting at transcriptional level for timely expression of genes enabling rapid responses to external stimuli and unfavorable conditions.
Abstract: Pseudomonas aeruginosa is an opportunistic pathogen affecting immunocompromised patients. It is known as the leading cause of morbidity and mortality in cystic fibrosis (CF) patients and as one of the leading causes of nosocomial infections. Due to a range of mechanisms for adaptation, survival and resistance to multiple classes of antibiotics, infections by P. aeruginosa strains can be life-threatening and it is emerging worldwide as public health threat. This review highlights the diversity of mechanisms by which P. aeruginosa promotes its survival and persistence in various environments and particularly at different stages of pathogenesis. We will review the importance and complexity of regulatory networks and genotypic-phenotypic variations known as adaptive radiation by which P. aeruginosa adjusts physiological processes for adaptation and survival in response to environmental cues and stresses. Accordingly, we will review the central regulatory role of quorum sensing and signaling systems by nucleotide-based second messengers resulting in different lifestyles of P. aeruginosa. Furthermore, various regulatory proteins will be discussed which form a plethora of controlling systems acting at transcriptional level for timely expression of genes enabling rapid responses to external stimuli and unfavorable conditions. Antibiotic resistance is a natural trait for P. aeruginosa and multiple mechanisms underlying different forms of antibiotic resistance will be discussed here. The importance of each mechanism in conferring resistance to various antipseudomonal antibiotics and their prevalence in clinical strains will be described. The underlying principles for acquiring resistance leading pan-drug resistant strains will be summarized. A future outlook emphasizes the need for collaborative international multidisciplinary efforts to translate current knowledge into strategies to prevent and treat P. aeruginosa infections while reducing the rate of antibiotic resistance and avoiding the spreading of resistant strains.
849 citations
Cites background from "Role of exopolysaccharides in Pseud..."
...The various exopolysaccharides and eDNA were shown to interactively contribute to the biofilm architecture (Ghafoor et al., 2011)....
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...These EPS play an important role in resistance to immune responses and antibiotic treatments (Ghafoor et al., 2011; Gellatly and Hancock, 2013; Strempel et al., 2013)....
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TL;DR: 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.
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.
572 citations
Cites background or result from "Role of exopolysaccharides in Pseud..."
...These studies, corroborated by more recent work, demonstrate that the Psl and Pel PSs provide attachment and structural support for nonmucoid and mucoid biofilms (116, 117), while alginate contributes to generation of a unique architecture (112, 114, 115)....
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...aeruginosa alginate, demonstrating that mucoid biofilms contain more viable cells than nonmucoid biofilms and are more resistant to DNase treatment (116, 117)....
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TL;DR: This review will focus on various polysaccharides as well as additional Pseudomonas biofilm matrix components, focusing on structure-function relationships, regulation, and the role of individual matrix molecules in niche biology.
Abstract: Biofilms are a predominant form of growth for bacteria in the environment and in the clinic. Critical for biofilm development are adherence, proliferation, and dispersion phases. Each of these stages includes reinforcement by, or modulation of, the extracellular matrix. Pseudomonas aeruginosa has been a model organism for the study of biofilm formation. Additionally, other Pseudomonas species utilize biofilm formation during plant colonization and environmental persistence. Pseudomonads produce several biofilm matrix molecules, including polysaccharides, nucleic acids, and proteins. Accessory matrix components shown to aid biofilm formation and adaptability under varying conditions are also produced by pseudomonads. Adaptation facilitated by biofilm formation allows for selection of genetic variants with unique and distinguishable colony morphology. Examples include rugose small-colony variants and wrinkly spreaders (WS), which over produce Psl/Pel or cellulose, respectively, and mucoid bacteria that over produce alginate. The well-documented emergence of these variants suggests that pseudomonads take advantage of matrix-building subpopulations conferring specific benefits for the entire population. This review will focus on various polysaccharides as well as additional Pseudomonas biofilm matrix components. Discussions will center on structure–function relationships, regulation, and the role of individual matrix molecules in niche biology.
494 citations
Cites background from "Role of exopolysaccharides in Pseud..."
...Ghafoor et al. (2011) show that greater Pel production occurs in the absence of Psl....
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TL;DR: This study evaluated a range of clinical and environmental P.aeruginosa isolates for their dependence on Pel and Psl for biofilm development and revealed both unique and redundant roles for two distinct biofilm exopolysaccharides.
Abstract: Extracellular polysaccharides comprise a major component of the biofilm matrix. Many species that are adept at biofilm formation have the capacity to produce multiple types of polysaccharides. Pseudomonas aeruginosa produces at least three extracellular polysaccharides, alginate, Pel and Psl, that have been implicated in biofilm development. Non-mucoid strains can use either Pel or Psl as the primary matrix structural polysaccharide. In this study, we evaluated a range of clinical and environmental P.aeruginosa isolates for their dependence on Pel and Psl for biofilm development. Mutational analysis demonstrates that Psl plays an important role in surface attachment for most isolates. However, there was significant strain-to-strain variability in the contribution of Pel and Psl to mature biofilm structure. This analysis led us to propose four classes of strains based upon their Pel and Psl functional and expression profiles. Our data also suggest that Pel and Psl can serve redundant functions as structural scaffolds in mature biofilms. We propose that redundancy could help preserve the capacity to produce a biofilm when exopolysaccharide genes are subjected to mutation. To test this, we used PAO1, a common lab strain that primarily utilizes Psl in the matrix. As expected, a psl mutant strain initially produced a poor biofilm. After extended cultivation, we demonstrate that this strain acquired mutations that upregulated expression of the Pel polysaccharide, demonstrating the utility of having a redundant scaffold exopolysaccharide. Collectively, our studies revealed both unique and redundant roles for two distinct biofilm exopolysaccharides.
460 citations
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Abstract: Bacterial biofilms are structured communities of cells enclosed in self-produced hydrated polymeric matrix adherent to an inert or living surface ([1][1]). Formation of these sessile communities and their inherent resistance to antibiotics and host immune attack are at the root of many persistent
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"Role of exopolysaccharides in Pseud..." refers background in this paper
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