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Rosário Oliveira - One of the best experts on this subject based on the ideXlab platform.
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The role of Exopolymers produced by Sphingomonas paucimobilis in biofilm formation and composition
Biofouling, 2000Co-Authors: Joana Azeredo, Rosário OliveiraAbstract:Exopolymers have been associated with the initial adhesion of bacteria, which is the primary step for biofilm formation. Moreover, the polymeric matrix of biofilms has a considerable influence on some of the most important physical and physiological properties of biofilms. The role of extracellular polymers in biofilm formation was studied using three mutants of Sphingomonas paucimobilis with increasing capabilities for Exopolymer production. The physical, biochemical and physiological properties of three different layers of each biofilm were determined. The layers were detached by submitting the biofilm to increasing shear stress. The results revealed that the presence of Exopolymers in the growth medium was essential for biofilm formation. The mutant producing the highest amount of Exopolymer formed very thick biofilms, while the biofilms formed by the medium Exopolymer producer were on average 8 times thinner. The lowest Exopolymer producer did not form biofilm. In both types of biofilms, Exopolymer de...
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The role of Exopolymers in the attachment of sphingomonas paucimobilis
Biofouling, 2000Co-Authors: Joana Azeredo, Rosário OliveiraAbstract:The importance of Exopolymers in the adhesion of Sphingomonas paucimobilis was established by studying the attachment to glass of three mutants with defective gellan production. The attachment assays were performed in either phosphate buffered saline (controls) or in the Exopolymeric solutions produced by the mutants. The Exopolymer was found to have surface active properties, changing the glass surface from hydrophilic to hydrophobic, making adhesion thermodynamically favourable. Only the cells that had a substantial polymeric layer surrounding their walls were able to significantly colonise glass coated with the Exopolymer. It is hypothesised that the Exopolymer bound to the glass and the Exopolymer present at the surface of the bacteria bound together, overcoming the energy barrier created by the negative charge of both surfaces. It is concluded that the Exopolymer from S. paucimobilis has a dual role in the process of adhesion by both coating the surface thereby strengthening adhesion and by enhancing...
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Exopolymers in bacterial adhesion: interpretation in terms of DLVO and XDLVO theories
Colloids and Surfaces B: Biointerfaces, 1999Co-Authors: Joana Azeredo, Joost Visser, Rosário OliveiraAbstract:Exopolymers have an important role in bacterial adhesion and are associated with irreversible adhesion. Moreover, they can coat surfaces enhancing or avoiding bacterial colonisation. To study the role of Exopolymers in the adhesion of bacteria to glass, three mutants of Sphingomonas paucimobilis (which are high (TR), medium (CV) and low (F72) Exopolymer producers), were used. The adhesion tests were performed in phosphate saline buffers and in solutions of the Exopolymer produced by each mutant. The DLVO theory was able to explain the results in phosphate saline buffers, although this theory could not explain the results obtained in the presence of the Exopolymer. The XDLVO theory enabled the interpretation of the results in the presence of the Exopolymer, where hydrophobic interactions played an important role. However, polymeric interactions that are not taken into account in these two theories are also expected to be determinant in the adhesion process. © 1999 Elsevier Science B.V. All rights reserved.
Justin R. Seymour - One of the best experts on this subject based on the ideXlab platform.
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Bacteria-mediated aggregation of the marine phytoplankton Thalassiosira weissflogii and Nannochloropsis oceanica
Journal of Applied Phycology, 2020Co-Authors: Nhan-an T. Tran, Bojan Tamburic, Christian R. Evenhuis, Justin R. SeymourAbstract:The ecological relationships between heterotrophic bacteria and marine phytoplankton are complex and multifaceted, and in some instances include the bacteria-mediated aggregation of phytoplankton cells. It is not known to what extent bacteria stimulate aggregation of marine phytoplankton, the variability in aggregation capacity across different bacterial taxa or the potential role of algogenic Exopolymers in this process. Here we screened twenty bacterial isolates, spanning nine orders, for their capacity to stimulate aggregation of two marine phytoplankters, Thalassiosira weissflogii and Nannochloropsis oceanica . In addition to phytoplankton aggregation efficiency, the production of Exopolymers was measured using Alcian Blue. Bacterial isolates from the Rhodobacterales , Flavobacteriales and Sphingomonadales orders stimulated the highest levels of cell aggregation in phytoplankton cultures. When co-cultured with bacteria, Exopolymer concentration accounted for 34.1% of the aggregation observed in T. weissflogii and 27.7% of the aggregation observed in N. oceanica . Bacteria-mediated aggregation of phytoplankton has potentially important implications for mediating vertical carbon flux in the ocean and in extracting phytoplankton cells from suspension for biotechnological applications.
Joana Azeredo - One of the best experts on this subject based on the ideXlab platform.
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The role of Exopolymers produced by Sphingomonas paucimobilis in biofilm formation and composition
Biofouling, 2000Co-Authors: Joana Azeredo, Rosário OliveiraAbstract:Exopolymers have been associated with the initial adhesion of bacteria, which is the primary step for biofilm formation. Moreover, the polymeric matrix of biofilms has a considerable influence on some of the most important physical and physiological properties of biofilms. The role of extracellular polymers in biofilm formation was studied using three mutants of Sphingomonas paucimobilis with increasing capabilities for Exopolymer production. The physical, biochemical and physiological properties of three different layers of each biofilm were determined. The layers were detached by submitting the biofilm to increasing shear stress. The results revealed that the presence of Exopolymers in the growth medium was essential for biofilm formation. The mutant producing the highest amount of Exopolymer formed very thick biofilms, while the biofilms formed by the medium Exopolymer producer were on average 8 times thinner. The lowest Exopolymer producer did not form biofilm. In both types of biofilms, Exopolymer de...
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The role of Exopolymers in the attachment of sphingomonas paucimobilis
Biofouling, 2000Co-Authors: Joana Azeredo, Rosário OliveiraAbstract:The importance of Exopolymers in the adhesion of Sphingomonas paucimobilis was established by studying the attachment to glass of three mutants with defective gellan production. The attachment assays were performed in either phosphate buffered saline (controls) or in the Exopolymeric solutions produced by the mutants. The Exopolymer was found to have surface active properties, changing the glass surface from hydrophilic to hydrophobic, making adhesion thermodynamically favourable. Only the cells that had a substantial polymeric layer surrounding their walls were able to significantly colonise glass coated with the Exopolymer. It is hypothesised that the Exopolymer bound to the glass and the Exopolymer present at the surface of the bacteria bound together, overcoming the energy barrier created by the negative charge of both surfaces. It is concluded that the Exopolymer from S. paucimobilis has a dual role in the process of adhesion by both coating the surface thereby strengthening adhesion and by enhancing...
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Exopolymers in bacterial adhesion: interpretation in terms of DLVO and XDLVO theories
Colloids and Surfaces B: Biointerfaces, 1999Co-Authors: Joana Azeredo, Joost Visser, Rosário OliveiraAbstract:Exopolymers have an important role in bacterial adhesion and are associated with irreversible adhesion. Moreover, they can coat surfaces enhancing or avoiding bacterial colonisation. To study the role of Exopolymers in the adhesion of bacteria to glass, three mutants of Sphingomonas paucimobilis (which are high (TR), medium (CV) and low (F72) Exopolymer producers), were used. The adhesion tests were performed in phosphate saline buffers and in solutions of the Exopolymer produced by each mutant. The DLVO theory was able to explain the results in phosphate saline buffers, although this theory could not explain the results obtained in the presence of the Exopolymer. The XDLVO theory enabled the interpretation of the results in the presence of the Exopolymer, where hydrophobic interactions played an important role. However, polymeric interactions that are not taken into account in these two theories are also expected to be determinant in the adhesion process. © 1999 Elsevier Science B.V. All rights reserved.
R Avci - One of the best experts on this subject based on the ideXlab platform.
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Study of the interaction of sulphate-reducing bacteria Exopolymers with iron using X-ray photoelectron spectroscopy and time-of-flight secondary ionisation mass spectrometry.
Journal of microbiological methods, 1999Co-Authors: I B Beech, V Zinkevich, R Tapper, R Gubner, R AvciAbstract:Time-of-flight secondary ionisation mass spectrometry and X-ray photoelectron spectroscopy were employed to determine the interaction of crude extracellular polymeric substances recovered from static batch cultures of two isolates of marine sulphate-reducing bacteria of the genus Desulfovibrio, grown in the presence of and without mild steel surfaces, with Fe ions released from steel. The results demonstrated that Exopolymers synthesised by different strains of sulphate-reducers varied in their ability to bind iron originating from steel. Based on the X-ray photoelectron spectroscopy analysis it is proposed that Fe released from steel was associated with bacterial Exopolymers such as Fe(III) ion. The application of surface science techniques to study Exopolymer/metal interaction allowed quantitative evaluation of Fe binding using small sample size.
Christian R. Evenhuis - One of the best experts on this subject based on the ideXlab platform.
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Bacteria-mediated aggregation of the marine phytoplankton Thalassiosira weissflogii and Nannochloropsis oceanica
Journal of Applied Phycology, 2020Co-Authors: Nhan-an T. Tran, Bojan Tamburic, Christian R. Evenhuis, Justin R. SeymourAbstract:The ecological relationships between heterotrophic bacteria and marine phytoplankton are complex and multifaceted, and in some instances include the bacteria-mediated aggregation of phytoplankton cells. It is not known to what extent bacteria stimulate aggregation of marine phytoplankton, the variability in aggregation capacity across different bacterial taxa or the potential role of algogenic Exopolymers in this process. Here we screened twenty bacterial isolates, spanning nine orders, for their capacity to stimulate aggregation of two marine phytoplankters, Thalassiosira weissflogii and Nannochloropsis oceanica . In addition to phytoplankton aggregation efficiency, the production of Exopolymers was measured using Alcian Blue. Bacterial isolates from the Rhodobacterales , Flavobacteriales and Sphingomonadales orders stimulated the highest levels of cell aggregation in phytoplankton cultures. When co-cultured with bacteria, Exopolymer concentration accounted for 34.1% of the aggregation observed in T. weissflogii and 27.7% of the aggregation observed in N. oceanica . Bacteria-mediated aggregation of phytoplankton has potentially important implications for mediating vertical carbon flux in the ocean and in extracting phytoplankton cells from suspension for biotechnological applications.
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Bacteria-mediated aggregation of the marine phytoplankton Thalassiosira weissflogii and Nannochloropsis oceanica
'Organisation for Economic Co-Operation and Development (OECD)', 2020Co-Authors: Tran Nhan-an, Tamburic B, Christian R. EvenhuisAbstract:The ecological relationships between heterotrophic bacteria and marine phytoplankton are complex and multifaceted, and in some instances include the bacteria-mediated aggregation of phytoplankton cells. It is not known to what extent bacteria stimulate aggregation of marine phytoplankton, the variability in aggregation capacity across different bacterial taxa, or the potential role of algogenic Exopolymers in this process. Here we screened twenty bacterial isolates, spanning nine orders, for their capacity to stimulate aggregation of two marine phytoplankton, Thalassiosira weissflogii and Nannochloropsis oceanica. In addition to phytoplankton aggregation efficiency, the production of Exopolymers was measured using Alcian blue. Bacterial isolates from the Rhodobacterales, Flavobacteriales and Sphingomonadales orders stimulated the highest levels of cell aggregation in phytoplankton cultures. When co-cultured with bacteria, Exopolymer concentration accounted for 34.1% of the aggregation observed in T. weissflogii and 27.7% of the aggregation observed in N. oceanica. Bacteria-mediated aggregation of phytoplankton has potentially important implications for mediating vertical carbon flux in the ocean and in extracting phytoplankton cells from suspension for biotechnological applications