Identification of N -acyl homoserine lactones produced by Gluconacetobacter diazotrophicus PAL5 cultured in complex and
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ORIGINAL PAPER
Identification of N-acyl homoserine lactones produced by Gluconacetobacter diazotrophicus PAL5 cultured in complex and synthetic media Carlos G. Nieto-Pen˜alver • Elisa V. Bertini Lucı´a I. C. de Figueroa
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Received: 12 October 2011 / Revised: 19 December 2011 / Accepted: 22 December 2011 / Published online: 18 February 2012 Ó Springer-Verlag 2012
Abstract The endophytic diazotrophic Gluconacetobacter diazotrophicus PAL5 was originally isolated from sugarcane (Saccharum officinarum). The biological nitrogen fixation, phytohormones secretion, solubilization of mineral nutrients and phytopathogen antagonism allow its classification as a plant growth-promoting bacterium. The recent genomic sequence of PAL5 unveiled the presence of a quorum sensing (QS) system. QS are regulatory mechanisms that, through the production of signal molecules or autoinducers, permit a microbial population the regulation of the physiology in a coordinated manner. The most studied autoinducers in gram-negative bacteria are the N-acyl homoserine lactones (AHLs). The usage of biosensor strains evidenced the presence of AHL-like molecules in cultures of G. diazotrophicus PAL5 grown in complex and synthetic media. Analysis of AHLs performed by LC-APCI-MS permitted the identification of eight different signal molecules, including C6-, C8-, C10-, C12- and C14HSL. Mass spectra confirmed that this diazotrophic strain also synthesizes autoinducers with carbonyl substitutions in the acyl chain. No differences in the profile of AHLs could be determined under both culture conditions. However,
Communicated by Shuang-Jiang Liu. C. G. Nieto-Pen˜alver (&) E. V. Bertini L. I. C. de Figueroa PROIMI, CONICET (Planta Piloto de Procesos Industriales Microbiolo´gicos), Av. Belgrano y Caseros, T4001MVB Tucuma´n, Argentina e-mail: [email protected] C. G. Nieto-Pen˜alver L. I. C. de Figueroa Instituto de Microbiologı´a, Facultad de Bioquı´mica, Quı´mica y Farmacia, Universidad Nacional de Tucuma´n, Tucuma´n, Argentina
although the level of short-chain AHLs was not affected, a decrease of 30% in the production of long-chain AHLs could be measured in synthetic medium. Keywords Gluconacetobacter diazotrophicus Quorum sensing N-Acyl homoserine lactone Autoinducer Diazotrophic
Introduction Gluconacetobacter diazotrophicus is an endophytic and diazotrophic gram-negative bacterium originally isolated from sugarcane. It has also been found in association with other sucrose-rich crops, such as sweet potato, sweet sorghum, pineapple, banana and coffee (Reis et al. 1994; Saravanan et al. 2008; Martı´nez et al. 2003; JimenezSalgado et al. 1997). Several important biotechnological features related to plant growth promotion have been described for this Alphaproteobacterium. In addition to its capacity to fix atmospheric nitrogen (Stephan et al. 1991), it secretes phytohormones such as auxins and gibberellins (Bastia´n et al. 1998); it inhibits the growth of the phytopathogens Xanthomonas albilineans, Fusarium sp. and Helminthosporium carbonum
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