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Interaction between extracellular lipase LipA and the polysaccharide alginate of Pseudomonas aeruginosa.

Tielen P, Kuhn H, Rosenau F, Jaeger KE, Flemming HC, Wingender J - BMC Microbiol. (2013)

Bottom Line: This effect was influenced by the chemical properties of the alginate molecules and was enhanced by the presence of O-acetyl groups in the alginate chain.This represents a physiological advantage for the cells.Especially in the biofilm lifestyle, the enzyme is retained near the cell surface, with the catalytic centre exposed towards the substrate and is protected from denaturation and proteolytic degradation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Aquatic Microbiology, University of Duisburg-Essen, Faculty of Chemistry, Biofilm Centre, Essen, Germany. p.tielen@tu-bs.de

ABSTRACT

Background: As an opportunistic human pathogen Pseudomonas aeruginosa is able to cause acute and chronic infections. The biofilm mode of life significantly contributes to the growth and persistence of P. aeruginosa during an infection process and mediates the pathogenicity of the bacterium. Within a biofilm mucoid strains of P. aeruginosa simultaneously produce and secrete several hydrolytic enzymes and the extracellular polysaccharide alginate. The focus of the current study was the interaction between extracellular lipase LipA and alginate, which may be physiologically relevant in biofilms of mucoid P. aeruginosa.

Results: Fluorescence microscopy of mucoid P. aeruginosa biofilms were performed using fluorogenic lipase substrates. It showed a localization of the extracellular enzyme near the cells. A microtiter plate-based binding assay revealed that the polyanion alginate is able to bind LipA. A molecular modeling approach showed that this binding is structurally based on electrostatic interactions between negatively charged residues of alginate and positively charged amino acids of the protein localized opposite of the catalytic centre. Moreover, we showed that the presence of alginate protected the lipase activity by protection from heat inactivation and from degradation by the endogenous, extracellular protease elastase LasB. This effect was influenced by the chemical properties of the alginate molecules and was enhanced by the presence of O-acetyl groups in the alginate chain.

Conclusion: We demonstrate that the extracellular lipase LipA from P. aeruginosa interacts with the polysaccharide alginate in the self-produced extracellular biofilm matrix of P. aeruginosa via electrostatic interactions suggesting a role of this interaction for enzyme immobilization and accumulation within biofilms. This represents a physiological advantage for the cells. Especially in the biofilm lifestyle, the enzyme is retained near the cell surface, with the catalytic centre exposed towards the substrate and is protected from denaturation and proteolytic degradation.

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Proteolytic degradation of lipase LipA through endogenous LasB. Purified lipase LipA (18 ng/ml) from P. aeruginosa was incubated for 24 h at 37°C with 0.5 U purified LasB from P. aeruginosa (EMD4 Bioscience) in the absence and in the presence of bacterial alginate from P. aeruginosa SG81. A representative experiment of two independent experiments with standard deviations of the duplicates is shown. *** p < 0.001.
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Figure 5: Proteolytic degradation of lipase LipA through endogenous LasB. Purified lipase LipA (18 ng/ml) from P. aeruginosa was incubated for 24 h at 37°C with 0.5 U purified LasB from P. aeruginosa (EMD4 Bioscience) in the absence and in the presence of bacterial alginate from P. aeruginosa SG81. A representative experiment of two independent experiments with standard deviations of the duplicates is shown. *** p < 0.001.

Mentions: Another biological function of such interactions may be the stabilization of the enzyme and the protection from proteolytic degradation. To address this question, the stability of LipA in the presence of the endogenous elastase LasB purified from P. aeruginosa was tested (Figure 5).


Interaction between extracellular lipase LipA and the polysaccharide alginate of Pseudomonas aeruginosa.

Tielen P, Kuhn H, Rosenau F, Jaeger KE, Flemming HC, Wingender J - BMC Microbiol. (2013)

Proteolytic degradation of lipase LipA through endogenous LasB. Purified lipase LipA (18 ng/ml) from P. aeruginosa was incubated for 24 h at 37°C with 0.5 U purified LasB from P. aeruginosa (EMD4 Bioscience) in the absence and in the presence of bacterial alginate from P. aeruginosa SG81. A representative experiment of two independent experiments with standard deviations of the duplicates is shown. *** p < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3733896&req=5

Figure 5: Proteolytic degradation of lipase LipA through endogenous LasB. Purified lipase LipA (18 ng/ml) from P. aeruginosa was incubated for 24 h at 37°C with 0.5 U purified LasB from P. aeruginosa (EMD4 Bioscience) in the absence and in the presence of bacterial alginate from P. aeruginosa SG81. A representative experiment of two independent experiments with standard deviations of the duplicates is shown. *** p < 0.001.
Mentions: Another biological function of such interactions may be the stabilization of the enzyme and the protection from proteolytic degradation. To address this question, the stability of LipA in the presence of the endogenous elastase LasB purified from P. aeruginosa was tested (Figure 5).

Bottom Line: This effect was influenced by the chemical properties of the alginate molecules and was enhanced by the presence of O-acetyl groups in the alginate chain.This represents a physiological advantage for the cells.Especially in the biofilm lifestyle, the enzyme is retained near the cell surface, with the catalytic centre exposed towards the substrate and is protected from denaturation and proteolytic degradation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Aquatic Microbiology, University of Duisburg-Essen, Faculty of Chemistry, Biofilm Centre, Essen, Germany. p.tielen@tu-bs.de

ABSTRACT

Background: As an opportunistic human pathogen Pseudomonas aeruginosa is able to cause acute and chronic infections. The biofilm mode of life significantly contributes to the growth and persistence of P. aeruginosa during an infection process and mediates the pathogenicity of the bacterium. Within a biofilm mucoid strains of P. aeruginosa simultaneously produce and secrete several hydrolytic enzymes and the extracellular polysaccharide alginate. The focus of the current study was the interaction between extracellular lipase LipA and alginate, which may be physiologically relevant in biofilms of mucoid P. aeruginosa.

Results: Fluorescence microscopy of mucoid P. aeruginosa biofilms were performed using fluorogenic lipase substrates. It showed a localization of the extracellular enzyme near the cells. A microtiter plate-based binding assay revealed that the polyanion alginate is able to bind LipA. A molecular modeling approach showed that this binding is structurally based on electrostatic interactions between negatively charged residues of alginate and positively charged amino acids of the protein localized opposite of the catalytic centre. Moreover, we showed that the presence of alginate protected the lipase activity by protection from heat inactivation and from degradation by the endogenous, extracellular protease elastase LasB. This effect was influenced by the chemical properties of the alginate molecules and was enhanced by the presence of O-acetyl groups in the alginate chain.

Conclusion: We demonstrate that the extracellular lipase LipA from P. aeruginosa interacts with the polysaccharide alginate in the self-produced extracellular biofilm matrix of P. aeruginosa via electrostatic interactions suggesting a role of this interaction for enzyme immobilization and accumulation within biofilms. This represents a physiological advantage for the cells. Especially in the biofilm lifestyle, the enzyme is retained near the cell surface, with the catalytic centre exposed towards the substrate and is protected from denaturation and proteolytic degradation.

Show MeSH
Related in: MedlinePlus