Biochemical and molecular insights into the antibiofilm and antivirulence effects of a B-phycoerythrin-rich extract from Porphyridium cruentum against Pseudomonas aeruginosa.

The growing resistance of Pseudomonas aeruginosa to conventional antibiotics has drawn increasing attention to antivirulence strategies that inhibit biofilm development and interfere with Quorum Sensing (QS) mechanisms. This study evaluated the biological activity of B-phycoerythrin (B-PE), a phycobiliprotein extracted from the red microalga Porphyridium cruentum, against Pseudomonas aeruginosa PAO1. This phycobiliprotein significantly inhibited biofilm formation by up to 62.4% and reduced performed biofilm by over 63% at 1/2 MIC, as quantified by crystal violet staining, causing notable morphological changes observed via epifluorescence microscopy. Furthermore, B-PE affected the production of virulence factors, decreasing pyocyanin and pyoverdine synthesis and reducing cell surface hydrophobicity. RT-qPCR analysis revealed significant downregulation of lasI, lasR, rhlI, rhlR, and mvfR, indicating modulation of multiple QS-associated regulatory components. These transcriptional changes, together with the observed alterations in QS-associated phenotypes, suggest that QS-associated regulation may contribute to the biological effects of the B-PE-rich extract. Overall, this study provides evidence for the antibiofilm and antivirulence potential of the B-PE-rich extract against Pseudomonas aeruginosa, supporting its further investigation as a naturally derived preparation for biofilm control and anti-infective applications.