In vitro and in silico evaluation of anti-quorum sensing activity of marine red seaweeds-Portieria hornemannii and Halymenia dilatata

The bacterial cell communicates from one cell to another by binding Auto-Inducers to specific receptors and their virulence factors, which are all products of their expression system. Therefore, this pathogenesis is controlled by disrupting the signal-response system. The current study assesses three maritime red seaweeds, including Portieria hornemannii and Halymenia dilatata, for their anti-Quorum Sensing (QS) activity against four bacteria. Those opportunistic pathogens cause severe QS-dependent biofilm formation and other virulences. In vitro, the study showed that biofilm formation in S. aureus was inhibited with 43.3%, 55% in Acinetobacter sp, 48% in E. coli, and 39. 2 % in K. pneumoniae by red seaweed extracts. The EPS production was also highly inhibited in Acinetobacter sp. with 41 % more than other bacteria. The efflux pump expressions and QS-dependent swimming motility were also effectively reduced. The present study targets the receptor proteins to prevent from binding of QS signals. Correspondingly, the in silico research predicts the binding affinity of bioactive compounds of seaweed extracts to the QS receptor proteins. The Hexamethyl Cyclotrisiloxane, Benzo[h]quinoline, 2,4-dimethyl, and 5-Methyl-2phenylindolizine compounds from H. dilatata, P. hornemannii, respectively, showed a higher binding affinity with receptor proteins such as AgrC (PDB ID: 4BXI) of S. aureus, SdiA (PDB ID:4LFU) of E. coli, Modelled SdiA protein of K. pneumoniae and Modelled AbaR protein of Acinetobacter sp. This study demonstrates the potential of seaweed against virulence and antibiotic resistance of pathogenic bacteria.