8 research outputs found
Study of natural or derivatives compounds which have an impact on biofouling
Le dĂ©veloppement de salissures marines (ou biofouling) est Ă lâorigine de nombreux problĂšmes Ă©conomiques et Ă©cologiques. Ces salissures marines sont constituĂ©es de microorganismes (bactĂ©ries, microalguesâŠ) formant le microfouling sur lequel va se dĂ©velopper le macrofouling constituĂ© de macroorganismes tels que les algues, coquillages et Ă©ponges. La formation de ces salissures va induire un ralentissement des navires provoquant une surconsommation de carburant. De plus, lâutilisation de revĂȘtements antisalissures ou peintures antifouling Ă base de mĂ©taux lourds et de biocides dans le passĂ© a conduit Ă des problĂšmes environnementaux. Lâobjectif de la thĂšse est de rechercher une alternative aux composĂ©s actuellement utilisĂ©s (cuivre) en respectant le milieu marin. Lâenvironnement est une source dâinspiration, une approche biomimĂ©tique pourrait ĂȘtre une stratĂ©gie de lutte efficace contre le biofouling. Dans une premiĂšre partie, un criblage dâune centaine de composĂ©s est rĂ©alisĂ© contre des souches bactĂ©riennes. Huit composĂ©s issus des deux familles : les batatasins et les hemibastadins sont Ă©tudiĂ©es en vue de comprendre leurs modes dâaction. Parmi les composĂ©s sĂ©lectionnĂ©s, la famille des hemibastadins comprenant le DiBromoHemiBastadin-1 (DBHB) a montrĂ© des propriĂ©tĂ©s antifouling prometteuses. En effet, cette molĂ©cule est capable dâinhiber 50 % la formation du biofilm avec une IC50= 6,44 ”g/mL pour la bactĂ©rie Pseudomonas aeruginosa PAO1 et une IC50 = 12,8 ”g/mL pour la bactĂ©rie marine Paracoccus sp. 4M6. Afin de comprendre le mode dâaction de cette molĂ©cule, son impact sur la communication bactĂ©rienne, le quorum sensing est Ă©tudiĂ© et le composĂ© DBHB est capable de lâinhiber. Dans une seconde partie, un autre groupe dâorganismes participant au microfouling est Ă©tudiĂ© : les microalgues. Afin dâĂ©valuer lâimpact de composĂ©s de la famille des hemibastadins et notamment du DBHB, lâadhĂ©sion et la formation de biofilm de microalgues sont Ă©tudiĂ©es. Le DBHB montre des inhibitions de lâadhĂ©sion et de la formation du biofilm uniquement envers la diatomĂ©e Cylindrotheca closterium. Une derniĂšre partie, sâest intĂ©ressĂ©e Ă lâĂ©valuation de revĂȘtements contenant six composĂ©s de la famille des batatasins et des hemibastadins sur le microfouling naturel. Une mĂ©thode dâimmersion de revĂȘtements en conditions contrĂŽlĂ©es (photobiorĂ©acteur) est mise au point afin de pallier aux contraintes environnementales. Lâensemble de cette Ă©tude a permis de mettre en Ă©vidence les propriĂ©tĂ©s antifouling du DBHB et de caractĂ©riser son mode dâaction. Ce composĂ© offre dâintĂ©ressantes voies dâĂ©tude dans la lutte contre le biofouling. De plus, lâapprofondissement des connaissances sur les procĂ©dĂ©s dâadhĂ©sion et de formation de biofilm de microalgues permet de dĂ©finir de nouvelles stratĂ©gies de lutte.Biofouling induces important economic and ecological problems. This phenomenon includes microorganisms (bacteria, microalgaeâŠ) giving the microfouling which allows the macrofouling development with algae, invertebrates and sponges. These organisms colonize every immersed surface as boat hull. The colonization induces reduced speed of ships and fuel overconsumption. In the past, the utilization of AF coatings with heavy metals or pesticides caused environmental problems. The purpose of the study is to find an alternative to AF compounds (copper) respecting the marine medium. The marine environment is an inspiration; a biomimetic approach could be an interesting strategy to inhibit biofouling. In a first part, a screening of one hundred compounds is realized against marine and terrestrial bacteria. Eight molecules from two families (batatasins and hemibastadins) are studied to understand the way of action. Among selected compounds, Dibromohemibastadin-1 (DBHB) from hemibastadin family shows promising AF activities. This molecule is able to inhibit the biofilm formation with an IC50 of 6,44 ”g/mL against the bacterium Pseudomonas aeruginosa PAO1 and 12,8 ”g/mL for the marine bacterium Paracoccus sp. 4M6. To identify the way of action of DBHB, the impact on the bacterial communication named quorum sensing is investigated. The molecule shows an anti-quorum sensing property. In a second part, another group participating at microfouling is studied: microalgae. In order to evaluate the impact of hemibastadin family in particular DBHB, microalgae adhesion and biofilm formation are characterized. DBHB induces inhibition only on the adhesion and the biofilm formation of the diatom Cylindrotheca closterium. The last part presents the formulation of coatings containing six compounds from the batatasin and hemibastadin families. These coatings have been immersed in a harbor to evaluate the impact on natural microfouling. Furthermore, a new method for the evaluation of AF coatings is developed in controlled conditions, in a photobioreactor. This method allows the evaluation of coatings on the formation of a mixed biofilm (bacteria and microalgae). This method has been established to avoid environmental constraints by immersion in natural condition. This study allows the characterization of the AF property of DBHB. This compound provides promising research path to limit biofouling. Moreover, the development of a test allowing adhesion and microalgae biofilm formation in dynamic condition improves the characterization of compounds activities
Ătude et valorisation de composĂ©s naturels ou dâanalogues de synthĂšse contrĂŽlant lâadhĂ©sion de salissures marines
Biofouling induces important economic and ecological problems. This phenomenon includes microorganisms (bacteria, microalgaeâŠ) giving the microfouling which allows the macrofouling development with algae, invertebrates and sponges. These organisms colonize every immersed surface as boat hull. The colonization induces reduced speed of ships and fuel overconsumption. In the past, the utilization of AF coatings with heavy metals or pesticides caused environmental problems. The purpose of the study is to find an alternative to AF compounds (copper) respecting the marine medium. The marine environment is an inspiration; a biomimetic approach could be an interesting strategy to inhibit biofouling. In a first part, a screening of one hundred compounds is realized against marine and terrestrial bacteria. Eight molecules from two families (batatasins and hemibastadins) are studied to understand the way of action. Among selected compounds, Dibromohemibastadin-1 (DBHB) from hemibastadin family shows promising AF activities. This molecule is able to inhibit the biofilm formation with an IC50 of 6,44 ”g/mL against the bacterium Pseudomonas aeruginosa PAO1 and 12,8 ”g/mL for the marine bacterium Paracoccus sp. 4M6. To identify the way of action of DBHB, the impact on the bacterial communication named quorum sensing is investigated. The molecule shows an anti-quorum sensing property. In a second part, another group participating at microfouling is studied: microalgae. In order to evaluate the impact of hemibastadin family in particular DBHB, microalgae adhesion and biofilm formation are characterized. DBHB induces inhibition only on the adhesion and the biofilm formation of the diatom Cylindrotheca closterium. The last part presents the formulation of coatings containing six compounds from the batatasin and hemibastadin families. These coatings have been immersed in a harbor to evaluate the impact on natural microfouling. Furthermore, a new method for the evaluation of AF coatings is developed in controlled conditions, in a photobioreactor. This method allows the evaluation of coatings on the formation of a mixed biofilm (bacteria and microalgae). This method has been established to avoid environmental constraints by immersion in natural condition. This study allows the characterization of the AF property of DBHB. This compound provides promising research path to limit biofouling. Moreover, the development of a test allowing adhesion and microalgae biofilm formation in dynamic condition improves the characterization of compounds activities.Le dĂ©veloppement de salissures marines (ou biofouling) est Ă lâorigine de nombreux problĂšmes Ă©conomiques et Ă©cologiques. Ces salissures marines sont constituĂ©es de microorganismes (bactĂ©ries, microalguesâŠ) formant le microfouling sur lequel va se dĂ©velopper le macrofouling constituĂ© de macroorganismes tels que les algues, coquillages et Ă©ponges. La formation de ces salissures va induire un ralentissement des navires provoquant une surconsommation de carburant. De plus, lâutilisation de revĂȘtements antisalissures ou peintures antifouling Ă base de mĂ©taux lourds et de biocides dans le passĂ© a conduit Ă des problĂšmes environnementaux. Lâobjectif de la thĂšse est de rechercher une alternative aux composĂ©s actuellement utilisĂ©s (cuivre) en respectant le milieu marin. Lâenvironnement est une source dâinspiration, une approche biomimĂ©tique pourrait ĂȘtre une stratĂ©gie de lutte efficace contre le biofouling. Dans une premiĂšre partie, un criblage dâune centaine de composĂ©s est rĂ©alisĂ© contre des souches bactĂ©riennes. Huit composĂ©s issus des deux familles : les batatasins et les hemibastadins sont Ă©tudiĂ©es en vue de comprendre leurs modes dâaction. Parmi les composĂ©s sĂ©lectionnĂ©s, la famille des hemibastadins comprenant le DiBromoHemiBastadin-1 (DBHB) a montrĂ© des propriĂ©tĂ©s antifouling prometteuses. En effet, cette molĂ©cule est capable dâinhiber 50 % la formation du biofilm avec une IC50= 6,44 ”g/mL pour la bactĂ©rie Pseudomonas aeruginosa PAO1 et une IC50 = 12,8 ”g/mL pour la bactĂ©rie marine Paracoccus sp. 4M6. Afin de comprendre le mode dâaction de cette molĂ©cule, son impact sur la communication bactĂ©rienne, le quorum sensing est Ă©tudiĂ© et le composĂ© DBHB est capable de lâinhiber. Dans une seconde partie, un autre groupe dâorganismes participant au microfouling est Ă©tudiĂ© : les microalgues. Afin dâĂ©valuer lâimpact de composĂ©s de la famille des hemibastadins et notamment du DBHB, lâadhĂ©sion et la formation de biofilm de microalgues sont Ă©tudiĂ©es. Le DBHB montre des inhibitions de lâadhĂ©sion et de la formation du biofilm uniquement envers la diatomĂ©e Cylindrotheca closterium. Une derniĂšre partie, sâest intĂ©ressĂ©e Ă lâĂ©valuation de revĂȘtements contenant six composĂ©s de la famille des batatasins et des hemibastadins sur le microfouling naturel. Une mĂ©thode dâimmersion de revĂȘtements en conditions contrĂŽlĂ©es (photobiorĂ©acteur) est mise au point afin de pallier aux contraintes environnementales. Lâensemble de cette Ă©tude a permis de mettre en Ă©vidence les propriĂ©tĂ©s antifouling du DBHB et de caractĂ©riser son mode dâaction. Ce composĂ© offre dâintĂ©ressantes voies dâĂ©tude dans la lutte contre le biofouling. De plus, lâapprofondissement des connaissances sur les procĂ©dĂ©s dâadhĂ©sion et de formation de biofilm de microalgues permet de dĂ©finir de nouvelles stratĂ©gies de lutte
Surface plasma treatment (Ar/CF4) decreases biofouling on polycarbonate surfaces
International audienceThe purpose of this study was to examine the impact of hydrophobicity, surface chemistry, and topography on bacterial and microalgal adhesion. To this end, the effects of surface plasma treatments (Argon and Tetrafluorocarbon) of polycarbonate substrates on bioadhesion were investigated in vitro. Surfaces were characterized by goniometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Two marine bacterial strains, a hydrophobic Pseudoalteromonas sp. 5M6 and a hydrophilic Paracoccus sp. 4M6 and two microalgae (Cylindrotheca closterium and Porphyridium purpureum) involved in marine biofouling were selected. Their adhesion on the substrates was observed and quantified using confocal laser scanning microscopy-microfluidic flow-cells. It was demonstrated that the combination of three parameters, namely surface energy, fluorination, and nanotopography, significantly decreases the adhesion of three microorganisms out of four (Pseudoalteromonas sp. 5M6, Cylindrotheca Closterium, and Porphyridium purpureum) whereas one parameter on its own is insufficient
A new method for evaluation of antifouling activity of molecules against microalgal biofilms using confocal laser scanning microscopy-microfluidic flow-cells
WOS:000464485900007Regulatory developments regarding antifouling molecules encourage the search for non-toxic substances. Evaluation tools must evolve to highlight anti-adhesion effects rather than growth inhibition. The work presented here aimed at developing a method based on confocal laser scanning microscopy-microfluidic flow-cells in order to characterize microalgal biofilms. The first part of the work was dedicated to the setting-up of experimental parameters allowing the production of microalgal biofilms. The results obtained showed that it was indeed possible to produce reproducibly biofilms. The size of microalgal strains appeared to be a key-parameter in the adhesion rate and cells adhesion strength. Cylindrotheca closterium cells adhered in lower amount but formed denser biofilms than Porphyridium purpureum. The second part of the work focused on the evaluation of a known antifouling molecule, dibromohemibastadin-1 (DBHB). A comparison with the conventionally used method, multi-well plates experiments, was established. The multi-well plates experiments allowed the determination of minimum inhibitory concentration (MIC) for growth and adhesion inhibition (around 80 mu M). The flow-cells combined with confocal laser scanning microscopy (CLSM) enabled the observation of biofilm, the determination of kinetics parameters of adhesion and an estimation of the adhesion strength
Anti-Biofilm Effect of Biodegradable Coatings Based on Hemibastadin Derivative in Marine Environment
International audienceDibromohemibastadin-1 (DBHB) is an already known potent inhibitor of blue mussel phenoloxidase (which is a key enzyme involved in bioadhesion). Within this study, the potentiality of DBHB against microfouling has been investigated. The activity of DBHB was evaluated on key strains of bacteria and microalgae involved in marine biofilm formation and bioassays assessing impact on growth, adhesion and biofilm formation were used. To assess the efficiency of DBHB when included in a matrix, DBHB varnish was prepared and the anti-microfouling activity of coatings was assessed. Both in vitro and in situ immersions were carried out. Confocal Laser Scanning Microscopy (CLSM) was principally used to determine the biovolume and average thickness of biofilms developed on the coatings. Results showed an evident efficiency of DBHB as compound and varnish to reduce the biofilm development. The mode of action seems to be based principally on a perturbation of biofilm formation rather than on a biocidal activity in the tested conditions
Anti-Biofilm Effect of Biodegradable Coatings Based on Hemibastadin Derivative in Marine Environment
Sponge-Inspired Dibromohemibastadin Prevents and Disrupts Bacterial Biofilms without Toxicity
Phidianidine A and Synthetic Analogues as Naturally Inspired Marine Antifoulants
Stationary and slow-moving marine organisms regularly employ a natural product chemical defense to prevent being colonized by marine micro- and macroorganisms. While these natural antifoulants can be structurally diverse, they often display highly conserved chemistries and physicochemical properties, suggesting a natural marine antifouling pharmacophore. In our current report, we investigate the marine natural product phidianidine A, which displays several chemical properties found in highly potent marine antifoulants. Phidianidine A and synthetic analogues were screened against the settlement and metamorphosis of Amphibalanus improvisus cyprids, and several of the compounds displayed inhibitory activities at low micromolar concentrations with IC50 values down to 0.7 ÎŒg/mL observed. The settlement study highlights that phidianidine A is a potent natural antifoulant and that the scaffold can be tuned to generate simpler and improved synthetic analogues. The bioactivity is closely linked to the size of the compound and to its basicity. The study also illustrates that active analogues can be prepared in the absence of the natural constrained 1,2,4-oxadiazole ring. A synthetic lead analogue of phidianidine A was incorporated in a coating and included in antifouling field trials, where it was shown that the coating induced potent inhibition of marine bacteria and microalgae settlement