Abstract
Bacterial biofilm formation can cause serious problems in clinical and industrial settings, which drives the development or screening of biofilm inhibitors. Some biofilm inhibitors have been screened from natural products or modified from natural compounds. Ginger has been used as a medicinal herb to treat infectious diseases for thousands of years, which leads to the hypothesis that it may contain chemicals inhibiting biofilm formation. To test this hypothesis, we evaluated ginger’s ability to inhibit Pseudomonas aeruginosa PA14 biofilm formation. A static biofilm assay demonstrated that biofilm development was reduced by 39–56% when ginger extract was added to the culture. In addition, various phenotypes were altered after ginger addition of PA14. Ginger extract decreased production of extracellular polymeric substances. This finding was confirmed by chemical analysis and confocal laser scanning microscopy. Furthermore, ginger extract formed noticeably less rugose colonies on agar plates containing Congo red and facilitated swarming motility on soft agar plates. The inhibition of biofilm formation and the altered phenotypes appear to be linked to a reduced level of a second messenger, bis-(3′-5′)-cyclic dimeric guanosine monophosphate. Importantly, ginger extract inhibited biofilm formation in both Gram-positive and Gram-negative bacteria. Also, surface biofilm cells formed with ginger extract detached more easily with surfactant than did those without ginger extract. Taken together, these findings provide a foundation for the possible discovery of a broad spectrum biofilm inhibitor.
Highlights
Most bacterial communities grow in 3-dimensional biofilm structures on surfaces in natural, clinical, and industrial settings [1]
The results suggested that the growth of PA14 was unaffected by the addition of ginger extract up to 10%
This study showed that ginger extract, similar to garlic extract [37], inhibits PA14 biofilm formation without affecting the growth of bacteria
Summary
Most bacterial communities grow in 3-dimensional biofilm structures on surfaces in natural, clinical, and industrial settings [1]. EPS attaches biofilm cells firmly to surfaces and protects them from harsh conditions. One noticeable feature of biofilm cells is increased resistance to detergent or biocides [3]. Possible reasons of this feature that may be due to the EPS layer include the limitation of the transport of the agents to interior bacterial cells in thick layers [4,5] and the reduction of available agents by adsorption into or reaction with the EPS matrix [6]. Biofilm formation can lead to substantial economic losses in engineering systems [8] owing to corrosion, reduced heat transfer, and increased friction
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