Abstract
Natural products derived from marine sponges have exhibited bioactivity and, in some cases, serve as potent quorum sensing inhibitory agents that prevent biofilm formation and attenuate virulence factor expression by pathogenic microorganisms. In this study, the inhibitory activity of the psammaplin-type compounds, psammaplin A (1) and bisaprasin (2), isolated from the marine sponge, Aplysinella rhax, are evaluated in quorum sensing inhibitory assays based on the Pseudomonas aeruginosa PAO1 lasB-gfp(ASV) and rhlA-gfp(ASV) biosensor strains. The results indicate that psammaplin A (1) showed moderate inhibition on lasB-gfp expression, but significantly inhibited the QS-gene promoter, rhlA-gfp, with IC50 values at 14.02 μM and 4.99 μM, respectively. In contrast, bisaprasin (2) displayed significant florescence inhibition in both biosensors, PAO1 lasB-gfp and rhlA-gfp, with IC50 values at 3.53 μM and 2.41 μM, respectively. Preliminary analysis suggested the importance of the bromotyrosine and oxime functionalities for QSI activity in these molecules. In addition, psammaplin A and bisaprasin downregulated elastase expression as determined by the standard enzymatic elastase assay, although greater reduction in elastase production was observed with 1 at 50 μM and 100 μM. Furthermore, the study revealed that bisaprasin (2) reduced biofilm formation in P. aeruginosa.
Highlights
Licensee MDPI, Basel, Switzerland.The discovery of antibiotics in the early 20th century was life saving for people suffering from infectious diseases [1]
The current study addresses the urgent need for new structural templates as quorum sensing inhibitors for the treatment of pathogenic bacterial infections through the use of various Quorum sensing (QS)-based bioassay platforms
We evaluated the ability of compounds 1 and 2 to inhibit biofilm formation in P. aeruginosa
Summary
The discovery of antibiotics in the early 20th century was life saving for people suffering from infectious diseases [1]. A World Health Organization (WHO, Geneva, Switzerland) report in 2019 concluded that, if the current trend is not averted, drug-resistant diseases could lead to the death of 10 million people each year by 2050 [24,25]. Quorum sensing (QS) is a cell-to-cell communication system used by many microorganisms to coordinate gene expression at the population level [27]. This communication system involves the secretion of chemical signaling molecules and once a sufficient concentration of signal molecules is achieved, this induces the expression of genes involved in a number of phenotypes, including biofilm formation [26,28], virulence factor production [29,30] and drug resistance mechanisms [31]
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