Physicochemical Interactions between Rhamnolipids and Pseudomonas aeruginosa Biofilm Layers

Abstract

This study investigated the physicochemical interactions between a rhamnolipid biosurfactant and a biofilm layer. A concentration of 300 μg mL(-1) of rhamnolipids, which is around the critical micelle concentration value (240 μg mL(-1)), showed great potential for reducing biofilm. The surface free energy between the rhamnolipids and biofilm layer decreased, as did the negative surface charge, due to the removal of negatively charged humic-like, protein-like, and fulvic acid-like substances. The carbohydrate and protein concentrations composed of extracellular polymeric substances decreased by 31.6% and 79.6%, respectively, at a rhamnolipid concentration of 300 μg mL(-1). In particular, rhamnolipids can interact with proteins, leading to a reduction of the N source and amide groups on the membrane. For carbohydrates, the component ratio of glucosamine was decreased, but the levels of glucose and mannose that form the majority of the carbohydrates remained unchanged. To our knowledge, the present study is the first attempt at studying the interactions of the two phases of rhamnolipids and the biofilm layer, and as such is expected to clarify the mechanism by which rhamnolipids lead to a reduction in biofilm.

Effects of rhamnolipids on the cell surface characteristics of Sphingomonas sp. GY2B and the biodegradation of phenanthrene

“…In the present study, the lamentous materials disappeared when high dose of rhamnolipids was added ( Fig. 3C-D), and the potential of rhamnolipids for reducing EPS has also been reported, [36][37][38] which indicated that the addition of rhamnolipids did not have a positive impact on the biodegradation of phenanthrene.…”

“…FTIR spectra have been widely used to determine the cell surface functional groups. 38,45 Thus, the changes in the functional groups of strain GY2B, with the addition of biosurfactants, were determined by FTIR spectra in the present study. The surface functional groups of strain GY2B were assigned according to the following studies 24,38 and summarized in the ESI.…”

Toll-like receptor 2 activation depends on lipopeptide shedding by bacterial surfactants

“…Moreover, agents with surfactant-like properties such as membrane-damaging antibiotics and disinfectants may help to mobilize TLR2 ligands in infections caused, for example, by S. aureus Agr mutants. PSMs are only found in staphylococci but the concept of MAMP release by surfactant–like molecules may be relevant also for other pathogens, for example, by the rhamnolipids of Pseudomonas aeruginosa 42 . Modulating the expression or treatment with surfactant-like agents may open new avenues for therapeutic interventions.…”

Disruption of Staphylococcus aureus biofilms using rhamnolipid biosurfactants

“…It is possible RL interacts with carbohydrates, promoting their solubilization or mobilization, thus favoring the detachment of biofilms. Studies regarding the interaction of RL biosurfactants with Pseudomonas aeruginosa biofilms revealed that, after RL treatment, the carbohydrate and protein content decreased by 31.6 and 79.6%, respectively (Kim et al, 2015), indicating a selective interaction of RL with proteins. In our study, the carbohydrates of milk-based biofilm were selectively removed; from these data, we can conclude that matrix composition has an important influence on RL disruption activity.…”