New 24-Membered Macrolactines from an Arctic Bacterium Bacillus amyloliquefaciens SCSIO 41392 and Their Anti-Pathogenicity Evaluation

Three new 24-membered macrolactines, amylomacrolactines A-C (<b>1</b>-<b>3</b>), along with two known compounds <b>4</b> and <b>5</b>, were isolated from the Arctic bacteria <i>Bacillus amyloliquefaciens</i> SCSIO 41392. The configurations of <b>1</b>-<b>3</b> were assigned by a combination of coupling constants, NOESY, and analysis of MM2-optimized conformation, as well as by comparison with reports in the literature. Compounds <b>1</b> and <b>2</b> showed quorum sensing (QS) inhibitory activities against the <i>Pseudomonas aeruginosa (P. aeruginosa)</i> PQS system and suppressed PQS-regulated virulence factor pyocyanin synthesis. In addition, compounds <b>3</b>-<b>5</b> affected the production of another essential virulence factor, siderophore of pyoverdine (PVD), in <i>P. aeruginosa</i>. More importantly, compound <b>5</b> showed an anti-biofilm activity against <i>P. aeruginosa</i>. Altogether, the isolated compounds displayed multiple bacterial virulence inhibition activities, which is worthy of further exploration for novel analogues in antimicrobial drug development.