Quorum  sensing N-acylhomoserine lactone signals affect nitrogen fixation in the cyanobacterium Anabaena sp. PCC7120

Authors

  • Manuel Romero,

    1. Departamento de Microbiología y Parasitología, Facultad de Biología-CIBUS, Universidad de Santiago de Compostela, Santiago de Compostela, Spain
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  • Alicia M. Muro-Pastor,

    1. Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Seville, Spain
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  • Ana Otero

    1. Departamento de Microbiología y Parasitología, Facultad de Biología-CIBUS, Universidad de Santiago de Compostela, Santiago de Compostela, Spain
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  • Editor: Karl Forchhammer

Correspondence: Ana Otero, Departamento de Microbiología y Parasitología, Facultad de Biología-CIBUS, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain. Tel.: +34 981 563 100, ext. 16913; fax: +34 981 528 006; e-mail: anamaria.otero@usc.es

Abstract

Bacteria secrete small signal molecules into the environment that induce self and neighbour gene expression. This phenomenon, termed quorum sensing, allows cooperative behaviours that increase the fitness of the group. The best-studied signal molecules are the N-acylhomoserine lactones (AHLs), secreted by a growing number of bacterial species including important pathogen species such as Pseudomonas aeruginosa. These molecules have recently been proposed to have properties other than those of signalling, functioning as iron quelants or antibiotics. As the presence of an acylase capable of inactivating long-chain AHLs in Anabaena sp. PCC7120 could constitute a defence mechanism against these molecules, in this work we analyse the effects of different AHLs varying in length and substitutions on the growth and nitrogen metabolism of the cyanobacterium Anabaena sp. PCC7120. All the AHLs tested strongly inhibited nitrogen fixation. The inhibition seems to take place at post-transcriptional level, as no effect on heterocyst differentiation or on the expression of nitrogenase was observed. Moreover, N-(3-oxodecanoyl)-l-homoserine lactone (OC10-HSL) showed a specific cytotoxic effect on this cyanobacterium in the presence of a combined nitrogen source, but the mechanism involved seems to be different from that described so far for tetramic acid derivatives of oxo-substituted AHLs. These results suggest a variety of new unexpected activities for AHLs, at least on cyanobacterial populations.

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