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Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.

ABSTRACT: A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N-acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL, N-hexanoyl-L-homoserine lactone, N-(3-oxo-hexanoyl)-homoserine lactone, and N-(3-oxo-octanoyl)-L-homoserine lactone (no absolute correlation between genomospecies of P. syringae and their ability to produce NAHL could be found). Six strains of fluorescent pseudomonads, belonging to the species P. chlororaphis, P. fluorescens, and P. putida, isolated from the plant rhizosphere produced different types of NAHL. In contrast, none of the strains isolated from soil samples were shown to produce NAHL. The gene encoding the NAHL synthase in P. syringae pv. maculicola was isolated by complementation of an NAHL-deficient Chromobacterium mutant. Sequence analysis revealed the existence of a luxI homologue that we named psmI. This gene is sufficient to confer NAHL synthesis upon its bacterial host and has strong homology to psyI and ahlI, two genes involved in NAHL production in P. syringae pv. tabaci and P. syringae pv. syringae, respectively. We identified another open reading frame that we termed psmR, transcribed convergently in relation to psmI and partly overlapping psmI; this gene encodes a putative LuxR regulatory protein. This gene organization, with luxI and luxR homologues facing each other and overlapping, has been found so far only in the enteric bacteria Erwinia and Pantoea and in the related species P. syringae pv. tabaci.

SUBMITTER: Elasri M

PROVIDER: S-EPMC92714 | biostudies-literature | 2001 Mar

REPOSITORIES: biostudies-literature

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Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.

Elasri M M Delorme S S Lemanceau P P Stewart G G Laue B B Glickmann E E Oger P M PM Dessaux Y Y

Applied and environmental microbiology 20010301 3

A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N-acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL, N-hexanoyl-L-homoserine lacton ...[more]

PMID: 11229911

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Project description:Production of phenazine antibiotics by the biological control bacterium Pseudomonas aureofaciens 30-84 is regulated in part by the PhzI/PhzR N-acyl-homoserine lactone (AHL) response system (L. S. Pierson III, V. D. Keppenne, and D. W. Wood, J. Bacteriol. 176:3966-3974, 1994; D. W. Wood and L. S. Pierson III, Gene 168:49-53, 1996). Two mutants, 30-84W and 30-84.A2, were isolated and were found to be deficient in the production of phenazine, protease, hydrogen cyanide (HCN), and the AHL signal N-hexanoyl-homoserine lactone. These mutants were not complemented by phzI, phzR, or the phenazine biosynthetic genes (phzFABCD) (L. S. Pierson III, T. Gaffney, S. Lam, and F. Gong, FEMS Microbiol. Lett. 134:299-307, 1995). A 2.2-kb region of the 30-84 chromosome which fully restored production of all of these compounds in strain 30-84W was identified. Nucleotide sequence analysis of this region revealed a single open reading frame encoding a predicted 213-amino-acid protein which is very similar to the global response regulator GacA. Strain 30-84.A2 was not complemented by gacA or any cosmid from a genomic library of strain 30-84 but was complemented by gacS (formerly lemA) homologs from Pseudomonas fluorescens Pf-5 (N. Corbel and J. E. Loper, J. Bacteriol. 177:6230-6236, 1995) and Pseudomonas syringae pv. syringae B728a (E. M. Hrabek and D. K. Willis, J. Bacteriol. 174:3011-3020, 1992). Transcription of phzR was not altered in either mutant; however, phzI transcription was eliminated in strains 30-84W and 30-84.A2. These results indicated that the GacS/GacA two-component signal transduction system of P. aureofaciens 30-84 controls the production of AHL required for phenazine production by mediating the transcription of phzI. Addition of exogenous AHL did not complement either mutant for phenazine production, indicating that the GacS/GacA global regulatory system controls phenazine production at multiple levels. Our results reveal for the first time a mechanism by which a two-component regulatory system and an AHL-mediated regulatory system interact.

Dataset Information

Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.

Publications

Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.

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