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Applied and Environmental Microbiology, October 2006, p. 6439-6451, Vol. 72, No. 10
0099-2240/06/$08.00+0     doi:10.1128/AEM.00398-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Pleiotropic Role of Quorum-Sensing Autoinducer 2 in Photorhabdus luminescens

Evelyne Krin,^1* Nesrine Chakroun,¹ Evelyne Turlin,¹ Alain Givaudan,² François Gaboriau,³ Isabelle Bonne,⁴ Jean-Claude Rousselle,⁵ Lionel Frangeul,⁶ Céline Lacroix,⁷ Marie-Françoise Hullo,¹ Laetitia Marisa,¹ Antoine Danchin,¹ and Sylviane Derzelle^1,

Unité de Génétique des Génomes Bactériens (URA2171), Institut Pasteur, Paris, France,¹ Laboratoire EMIP, Université Montpellier II, IFR122, Institut National de la Recherche Agronomique (UMR1133), 34095 Montpellier, France,² Inserm U522, Université Rennes 1, IFR 140, 35000 Rennes, France,³ Plate-Forme de Microscopie Electronique, Institut Pasteur, Paris, France,⁴ Pasteur Génopole Ile-de-France, Plate-Forme de Protéomique, Paris, France,⁵ Pasteur Génopole Ile-de-France, Intégration et Analyse Génomique, Paris, France,⁶ Pasteur Génopole Ile-de-France, Plate-Forme Puces à ADN, Paris, France⁷

Received 17 February 2006/ Accepted 15 July 2006

Bacterial virulence is an integrative process that may involve quorum sensing. In this work, we compared by global expression profiling the wild-type entomopathogenic Photorhabdus luminescens subsp. laumondii TT01 to a luxS-deficient mutant unable to synthesize the type 2 quorum-sensing inducer AI-2. AI-2 was shown to regulate more than 300 targets involved in most compartments and metabolic pathways of the cell. AI-2 is located high in the hierarchy, as it controls the expression of several transcriptional regulators. The regulatory effect of AI-2 appeared to be dose dependent. The luxS-deficient strain exhibited decreased biofilm formation and increased type IV/V pilus-dependent twitching motility. AI-2 activated its own synthesis and transport. It also modulated bioluminescence by regulating the synthesis of spermidine. AI-2 was further shown to increase oxidative stress resistance, which is necessary to overcome part of the innate immune response of the host insect involving reactive oxygen species. Finally, we showed that the luxS-deficient strain had attenuated virulence against the lepidopteran Spodoptera littoralis. We concluded that AI-2 is involved mainly in early steps of insect invasion in P. luminescens.

Supplemental material for this article may be found at http://aem.asm.org/.

Present address: AFSSA-LERQAP, Maisons-Alfort, France.

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