Abstract
The majority of the marine algal species, though completing their life cycle in seawater, are rarely susceptible to fouling, making them an important source of quorum sensing (QS) inhibitory substances. The separation and characterization of QS inhibitors are crucial for any potential application. Thirty marine macroalgae were tested for QS inhibition activity by using Chromobacterium violaceum CV026 as the reporter strain, and among them, Asparagopsis taxiformis showed antibacterial, as well as antiquorum, sensing activities. Cinnamaldehyde (75 mM) and methanol were used as positive and negative controls, respectively. The antiquorum sensing activity of A. taxiformis was further confirmed using the sensor strain, Serratia liquefaciens MG44, having green fluorescent protein (gfp). Methanolic extract of the alga was fractionated by solid phase extraction (SPE), and each fraction was tested for QS inhibition. Two types of activities were observed—zone of clearance (antibacterial activity) and zone of inhibition with or without finger-like projections (QS inhibition). Out of five SPE cartridges, Bond Elut PH showed clear separation of these two fractions. The Ion Cyclotron Resonance Fourier Transformation Mass Spectrometer (ICR-FT/MS) analysis of the fractions further supported the bioassay results. The presence of strong QS inhibitory compound in A. taxiformis indicates its potential use in antifouling preparations.
Highlights
Biofilms are organized communities of microbes sheathed in extracellular polymeric substances (EPS)
Thirty different marine macro algae belonging to three divisions were tested for quorum sensing inhibition using Chromobacterium violaceum C. violaceum 026 (CV026)
Thirty different marine macro algae were screened for quorum sensing inhibition (QSI) activities using Chromobacterium violaceum CV026 as the biological reporter
Summary
Biofilms are organized communities of microbes sheathed in extracellular polymeric substances (EPS). It has been found that quorum sensing inhibitors increase the susceptibility of bacterial biofilms to antibiotics in vitro and in vivo [4]. Biofilm causes adverse effects in several important structures, including water-supplying pipes, air ducts, catheters and fermenters in industries. It causes erosion, clogging and slippery coatings on the surface, as well as harmful contamination of bacteria [5,6]. Marine algae are endowed with effective defense mechanisms to avert biofilm formation, such as quorum sensing inhibition through metabolite production. The fractions were further subjected to ICR-FT/MS analysis This is the first report of the quorum sensing inhibition property of Asparagopsis taxiformis and the capability of different SPE cartridges to separate quorum sensing inhibitor and antibacterial compounds
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