Biofilm and Quorum-Sensing Inhibition by Novel Bacillus xiamenensis MM07 Endophytic Isolate from Paederia foetida to Combat Pseudomonas aeruginosa

This study investigated the antibiofilm and anti-quorum-sensing (QS) potential of endophyte extracts isolated from medicinal plants and their validation against Pseudomonas aeruginosa. Endophytes were isolated from the plants using the serial dilution method, and the extracts produced by these endophytes were screened for antimicrobial and biofilm-inhibition activity using assays. The efficient extract was biochemically characterized, followed by validation of its secondary metabolite content. Furthermore, QS-regulatory gene expression levels and microscopy were used to confirm inhibition of biofilm formation. A total of 12 cultures, including 8 bacterial and 4 fungal, were isolated and screened, demonstrating efficient antimicrobial activity (zone of inhibition of 18.8 mm) and 64.3% antibiofilm activity. The efficient endophyte isolated from Paederia foetida was identified as Bacillus xiamenensis MM07 by 16S rRNA gene sequencing. MM07 extract analyses by biochemical and Fourier transform infrared methods revealed the presence of diverse biomolecules. A dose-dependent inhibition was observed, achieving up to 83.5, 60.3, 73.2, 82.7, 83.2, and 15.1 in biofilm formation and exopolysaccharide, violacein, pyocyanin, protease, and alginate production, along with 63.2% swimming ability at 30 µg/mL, respectively. Gas chromatography-mass spectrometry analyses validated the presence of major secondary metabolites, including 3,3-dimethyl-4-methylamino-butan-2-one, 6-amino-2-methyl-, 1-iodo-2-methylundecane, and hexadecanoic acid, with the potential to inhibit biofilm and QS activity. Quantitative real-time polymerase chain reaction of QS regulatory genes (lasI, lasR, rhlI, and rhlR) and microscopy analysis confirmed the anti-QS properties, evidenced by a 40.3% decline in gene expression and biofilm inhibition by MM07 extract. These findings highlight the potential of novel B. xiamenensis MM07 endophyte from P. foetida as a sustainable source of biomolecules for combating biofilm-associated infections.