Abstract
Microbial cells are reversibly associated with surfaces in the form of biofilms. Adhesion is the mechanism used by the microorganisms to bind to a surface initially; no biofilm is formed without the initial adhesion. The aim of this work was to evaluate the efficacy of the rhamnolipids of Pseudomonas aeruginosa Rn19a in inhibiting the biofilms formed by the clinical isolates Escherichia coli I5, Pseudomonas aeruginosa E26, Enterococcus faecalis I27 on borosilicate coupons inside a Center for Disease Control and Prevention (CDC) reactor. The isolate E26 (P. aeruginosa) did not show an adverse effect on biofilm formation by the rhamnolipid presence and showed normal growth in all the conditions tested (dynamic and static growth). The Enterococcus faecalis I27 isolate decreased its biofilm formation ability in 2.2 log CFU/cm2 in static conditions by the addition of rhamnolipids and 3.0 log units in dynamic conditions. Finally, the E. coli I5 isolate was more susceptible to the influence of the borosilicate coupon covered with rhamnolipids. E5 reduced its biofilm formation capacity by 3.0 log CFU/cm2 units at static conditions by the rhamnolipid addition and 6.0 log units at dynamic conditions. Biofilm formation was also observed by Confocal Laser Scanning Microscopy. In summary, the application of rhamnolipids may be useful to prevent the initial adhesion of bacteria to borosilicate surfaces. At a minimum, rhamnolipids effectively inhibit or diminish adhesion to surfaces by biofilm-forming isolates that do not belong to the genus Pseudomonas.
Highlights
In aquatic environments, usually bacteria are growing as biofilms
Most of our results show an inhibitory effect of rhamnolipids on biofilms, which is similar to other reports [8,19,36]
The treatment of coupons with rhamnolipids (0.4% w/v) showed some changes in biofilms formation
Summary
Usually bacteria are growing as biofilms. Biofilm can be defined as a sessile community of microorganisms irreversibly linked to a substrate or interface or with each other; the microbial cells are integrated into an array of extracellular polymeric substances (EPS) produced by the community an altered phenotype in growth rate and genotype [1,2].The life cycle of biofilms includes the adhesion of individual cells to a surface, followed by the production of EPS that covers the cells and allows the formation of colonies, that when fully formed, can lead to the release of few cells in planktonic phenotypes, that can be dispersed in the surrounded area. Biofilm can be defined as a sessile community of microorganisms irreversibly linked to a substrate or interface or with each other; the microbial cells are integrated into an array of extracellular polymeric substances (EPS) produced by the community an altered phenotype in growth rate and genotype [1,2]. The life cycle of biofilms includes the adhesion of individual cells to a surface, followed by the production of EPS that covers the cells and allows the formation of colonies, that when fully formed, can lead to the release of few cells in planktonic phenotypes, that can be dispersed in the surrounded area. Biofilms are exceedingly difficult to remove and are, a cause of concern in medicine and industrial settings, among other environments [4]
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