Identification and characterization of a long-chain N-acyl homoserine lactone from Rhizobium sp. isolated from Zea x mays rhizosphere

The microbiological study of maize rhizosphere (Zea x mays) cultivated in Brazil led to the isolation of a bacterium, which was identified as Rhizobium sp. based upon 16 S rRNA analysis. The chemical study of fractions obtained from bacterium extract allowed the identification of the compound N-(3-oxo-tetradec-7-enoyl)-homoserine lactone (1) using uni and bidimensional nuclear magnetic resonance spectroscopy (NMR), gas chromatography coupled to low resolution electron impact mass spectrometry (GC–MS), and ultra-high resolution Qq-time-of-flight mass spectrometry (UHR-QqTOF-MS). Biological assays with the strains Agrobacterium tumefasciens A136 and Chromobacterium violaceum CV026 were also performed and showed negative results, corroborating the hypothesis of production of only the long chain acyl homoserine lactone (AHL) 1, and the lack of presence of short or medium chain homologues, as observed by instrumental GC–MS and NMR analyses. The chemotaxonomic relevance of the presence of long chain AHL in Rhizobiaceae was discussed.