Laue, B.E., Jiang, Y., Chhabra, S.R., Jacob, S., Stewart, G.S.A.B., Hardman, A., Downie, J.A., O'Gara, F., and Williams, P.;

2000

October

Microbiology

The biocontrol strain Pseudomonas fluorescens F113 produces the Rhizobium 'small' bacteriocin, N-(3-hydroxy-7-cis-tetradecenoyl)homoserine lactone, via HdtS, a putative novel N-acylhomoserine lactone synthase.

Published

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Pseudomonas fluorescens N-acylhomoserine lactone synthase Rhizobium N-(3-hydroxy-7-cis-tetradecenoyl)homoserine lactone acyltransferase ACYL-HOMOSERINE-LACTONE QUORUM-SENSING SYSTEM SIGNAL MOLECULES VIBRIO-FISCHERI VIRULENCE DETERMINANTS SECONDARY METABOLITES AUTOINDUCER SYNTHESIS S-ADENOSYLMETHIONINE STATIONARY-PHASE AERUGINOSA

146

2469

2480

Several different species of Pseudomonas produce N-acylhomoserine lactones (AHLs), quorum-sensing signal molecules which are involved in the cell-density-dependent control of secondary metabolite and virulence gene expression. When Pseudomonas fluorescens F113 was cross-streaked against AHL biosensors capable of sensitively detecting either short (C-4-C-8) or long (C-10-C-14) acyl chain AHLs, no activity was detectable. However, by extracting cell-free stationary-phase culture supernatants with dichloromethane followed by reverse-phase HPLC, three distinct fractions were obtained capable of activating the AHL biosensors. Three AHLs were subsequently characterized using high-resolution MS and chemical synthesis. These were (i) N-(3-hydroxy-7-cis-tetradecenoyl)homoserine lactone (30H,C-14:1-HSL), a molecule previously known as the Rhizobium leguminosarum small bacteriocin as a consequence of its growth inhibitory properties, (ii) N-decamoylhomoserine lactone (C-10-HSL) and (iii) N-hexanoylhomoserine lactone (C-6-HSL). A gene (hdtS) capable of directing synthesis of all three P, fluorescens AHLs in Escherichia coli was cloned and sequenced. In vitro transcription/translation of hdtS yielded a protein of approximately 33 kDa capable of directing the synthesis of 3OH,C-14:1-HSL, C-10-HSL and C-6-HSL in E. coli, HdtS does not belong to either of the known AHL synthase families (LuxI or LuxM) and is related to the lysophosphatidic acid acyltransferase family. HdtS may therefore constitute a member of a third protein family capable of AHL biosynthesis.