A Marine Mesorhizobium sp. Produces Structurally Novel Long-Chain N -Acyl- l -Homoserine Lactones

Abstract

ABSTRACT Our study focused on a Mesorhizobium sp. that is phylogenetically affiliated by 16S rRNA gene sequence to other marine and saline bacteria of this genus. Liquid chromatography-mass spectrometry investigations of the extract obtained from solid-phase extraction of cultures of this bacterium indicated the presence of several N -acyl homoserine lactones (AHLs), with chain lengths of C 10 to C 16 . Chromatographic separation of the active bacterial extract yielded extraordinarily large amounts of two unprecedented acylated homoserine lactones, 5- cis -3-oxo-C 12 -homoserine lactone (5- cis -3-oxo-C 12 -HSL) (compound 1) and 5- cis -C 12 -HSL (compound 2). Quorum-sensing activity of compounds 1 and 2 was shown in two different biosensor systems [ Escherichia coli MT102(pSB403) and Pseudomonas putida F117(pKR-C12)]. Furthermore, it was shown that both compounds can restore protease and pyoverdin production of an AHL-deficient Pseudomonas aeruginosa PAO1 lasI rhlI double mutant, suggesting that these signal molecules maybe used for intergenus signaling. In conclusion, these data indicate that the quorum-sensing activity of compounds 1 and 2 is modulated by the chain length and functional groups of the acyl moiety. Additionally, compound 1 showed antibacterial and cytotoxic activities.