Conversion to Mucoidy in Pseudomonas aeruginosa

Deretić, Vojo; Martin, Daniel W.; Schurr, Michael J.; Mudd, Michal H.; Hibler, N S; Curcic, R.; Boucher, J C

doi:10.1038/nbt1093-1133

Cited by 37 publications

(40 citation statements)

References 35 publications

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“…Capsular polysaccharides are secreted by both Gramnegative and Gram-positive bacteria to form a highly hydrated, negatively charged, protective glycocalyx surrounding the bacterium (44). Unlike extracellular polysaccharides such as alginate, involved in bacterial adhesion and biofilm formation of Pseudomonas aeruginosa (45,46), capsular polysaccharides help prevent immunological recognition, phagocytosis, and adhesion (5). Under conditions of stress, E. coli synthesizes colanic acid, a repeating polymer of glucose, galactose, fucose, glucuronic acid, and pyruvate forming a capsule around the E. coli cell surface (26,31).…”

Section: Resultsmentioning

confidence: 99%

Molecular determinants of bacterial adhesion monitored by atomic force microscopy

Razatos

Ong

Sharma

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

345

267

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Bacterial adhesion and the subsequent formation of biofilm are major concerns in biotechnology and medicine. The initial step in bacterial adhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic interactions. The precise manner in which the force of interaction is affected by cell surface components and by the physiochemical properties of materials is not well understood. Here, we show that atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution. Interactions between the cantilever tip and conf luent monolayers of isogenic strains of Escherichia coli mutants exhibiting subtle differences in cell surface composition were measured. It was shown that the adhesion force is affected by the length of core lipopolysaccharide molecules on the E. coli cell surface and by the production of the capsular polysaccharide, colanic acid. Furthermore, by modifying the atomic force microscope tip we developed a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest. This information will be critical for the design of materials that are resistant to bacterial adhesion.Bacterial adhesion onto inanimate surfaces is a critical issue in processes ranging from the biofouling of industrial equipment to dental decay to infections of biomaterials for medical use. Bacterial infections associated with the formation of biofilms refractile to antibiotic therapy is one of the main reasons for the failure of devices such as catheters, vascular grafts, joint prostheses, and heart valves (1-3). The first step in bacterial adhesion is the immediate attachment of bacteria onto a substratum which is a reversible, nonspecific process (3-5). This initial interaction between bacteria and artificial surfaces is a key determinant in biofilm formation. If the approach of bacteria to a surface is unfavorable, cells must overcome an energy barrier to establish direct contact with the surface. Only when bacteria are in close proximity to the surface do shortrange interactions become significant. Thereafter, proteinligand-binding events mediated by a plethora of microbial adhesins and in some cases the production of extracellular polymers render the binding process practically irreversible (6).Initial bacterial attraction or repulsion to a particular surface can be described in terms of colloidal interactions. Consequently, the force of interaction depends on physiochemical parameters such as surface-free energy and charge density (7-11). The propensity of bacteria to adhere onto surfaces has been estimated by counting the number of bacteria that remain attached to surfaces following incubation for a specified length of time (5, 12). This approach is qualitative, time consuming, and has low sensitivity. Moreover, the resulting number of adherent bacteria is determined by multiple factors in addition to long-range attractive/repulsive interactions. A direct and ...

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Section: Resultsmentioning

confidence: 99%

Molecular determinants of bacterial adhesion monitored by atomic force microscopy

Razatos

Ong

Sharma

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

345

267

View full text Add to dashboard Cite

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“…Although the initial colonizing P. aeruginosa strains are nonmucoid, they undergo conversion to a highly mucoid phenotype in later stages of the disease. Loss-of-function mutations in either mucA or mucB have been reported to convert P. aeruginosa to mucoidy, by increasing AlgU activity (11,12,25). In contrast, A. vinelandii strains produce alginate even in the absence of mutations in the mucABCD operon.…”

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confidence: 99%

“…In P. aeruginosa and A. vinelandii, the mucABCD genes are located downstream of the algU gene, forming part of the same transcriptional unit (26,43). It has been clearly shown elsewhere for P. aeruginosa that the AlgU activity is negatively regulated by the anti-sigma factor MucA (11,12,16,19,27,43,45) and, in an indirect manner, by MucB (27) and also that the mucD gene encodes a periplasmic protease which plays a central role in AlgU activation (4). MucC has been shown to play a role in AlgU regulation for P. aeruginosa, but its mechanism has not been elucidated (5).…”

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confidence: 99%

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Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

et al. 2000

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Azotobacter vinelandii produces the exopolysaccharide alginate, which is essential for its differentiation to desiccation-resistant cysts. In different bacterial species, the alternative sigma factor E regulates the expression of functions related to the extracytoplasmic compartments. In A. vinelandii and Pseudomonas aeruginosa, the E factor (AlgU) is essential for alginate production. In both bacteria, the activity of this sigma factor is regulated by the product of the mucA, mucB, mucC, and mucD genes. In this work, we studied the transcriptional regulation of the A. vinelandii algU-mucABCD gene cluster, as well as the role of the mucA and mucC gene products in alginate production. Our results show the existence of AlgU autoregulation and show that both MucA and MucC play a negative role in alginate production.

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“…The chronic pneumonia caused by P. aeruginosa is the leading cause of morbidity and mortality of CF patients (24). The mucoid phenotype of P. aeruginosa, characterized by production of the exopolysaccharide alginate, is almost exclusively associated with chronic CF pneumonia (10,15,26,43,60). Alginate, composed of a linear copolymer of ␤-D-mannuronic and ␣-L-guluronic acids (17,30,31), confers a selective advantage on P. aeruginosa in the CF patient lung.…”

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confidence: 99%

Identification of AlgR-Regulated Genes in Pseudomonas aeruginosa by Use of Microarray Analysis

et al. 2004

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The Pseudomonas aeruginosa transcriptional regulator AlgR controls a variety of different processes, including alginate production, type IV pilus function, and virulence, indicating that AlgR plays a pivotal role in the regulation of gene expression. In order to characterize the AlgR regulon, Pseudomonas Affymetrix GeneChips were used to generate the transcriptional profiles of (i) P. aeruginosa PAO1 versus its algR mutant in mid-logarithmic phase, (ii) P. aeruginosa PAO1 versus its algR mutant in stationary growth phase, and (iii) PAO1 versus PAO1 harboring an algR overexpression plasmid. Expression analysis revealed that, during mid-logarithmic growth, AlgR activated the expression of 58 genes while it repressed the expression of 37 others, while during stationary phase, it activated expression of 45 genes and repression of 14 genes. Confirmatory experiments were performed on two genes found to be AlgR repressed (hcnA and PA1557) and one AlgR-activated operon (fimU-pilVWXY1Y2). An S1 nuclease protection assay demonstrated that AlgR repressed both known hcnA promoters in PAO1. Additionally, direct measurement of hydrogen cyanide (HCN) production showed that P. aeruginosa PAO1 produced threefold-less HCN than did its algR deletion strain. AlgR also repressed transcription of two promoters of the uncharacterized open reading frame PA1557. Further, the twitching motility defect of an algR mutant was complemented by the fimTU-pilVWXY1Y2E operon, thus identifying the AlgR-controlled genes responsible for this defect in an algR mutant. This study identified four new roles for AlgR: (i) AlgR can repress gene transcription, (ii) AlgR activates the fimTU-pilVWXY1Y2E operon, (iii) AlgR regulates HCN production, and (iv) AlgR controls transcription of the putative cbb 3 -type cytochrome PA1557.

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Conversion to Mucoidy in Pseudomonas aeruginosa

Cited by 37 publications

References 35 publications

Molecular determinants of bacterial adhesion monitored by atomic force microscopy

Molecular determinants of bacterial adhesion monitored by atomic force microscopy

Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

Identification of AlgR-Regulated Genes in Pseudomonas aeruginosa by Use of Microarray Analysis

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