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1.
Appl Environ Microbiol ; 73(12): 4078-81, 2007 Jun.
Article in English | MEDLINE | ID: mdl-17468275

ABSTRACT

The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level.


Subject(s)
Acyl-Butyrolactones/metabolism , Body Temperature Regulation/physiology , Gene Expression Regulation, Enzymologic , Ligases/metabolism , Pectobacterium/physiology , Quorum Sensing/physiology , Base Sequence , DNA Primers , Ligases/genetics , Molecular Sequence Data , Plant Diseases/microbiology , Reverse Transcriptase Polymerase Chain Reaction , Sequence Analysis, DNA , Solanum tuberosum/microbiology , Temperature
2.
J Bacteriol ; 188(20): 7321-4, 2006 Oct.
Article in English | MEDLINE | ID: mdl-17015673

ABSTRACT

A cryptic plasmid of Methylobacterium extorquens AM1 was found to encode tslI, a truncated luxI homolog. tslI was shown to be expressed and to control transcription of the acyl-homoserine lactone (HSL) synthase gene msaI and thus, indirectly, acyl-HSL production. In addition, tslI was found to positively regulate extracellular polysaccharide production.


Subject(s)
Adaptation, Physiological/genetics , Bacterial Proteins/physiology , Carbohydrates/biosynthesis , Ligases/biosynthesis , Methylobacterium extorquens/physiology , Plasmids/genetics , Transcription Factors/physiology , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/analysis , Amino Acid Sequence , Bacterial Proteins/genetics , Gene Expression Regulation, Bacterial , Ligases/genetics , Methylobacterium extorquens/genetics , Molecular Sequence Data , RNA, Bacterial/analysis , RNA, Messenger/analysis , Sequence Alignment , Transcription Factors/genetics , Transcription, Genetic
3.
FEBS Lett ; 580(2): 561-7, 2006 Jan 23.
Article in English | MEDLINE | ID: mdl-16412429

ABSTRACT

Acyl-homoserine lactones (acyl-HSLs) have emerged as important regulatory molecules for many gram-negative bacteria. We have found that Methylobacterium extorquens AM1, a member of the pink-pigmented facultative methylotrophs commonly present on plant surfaces, produces several acyl-HSLs depending upon the carbon source. A novel HSL was discovered with a double unsaturated carbon chain (N-(tetradecenoyl)) (C14:2) and characterized by MS and proton NMR. This long-chain acyl-HSL is synthesized by MlaI that also directs synthesis of C14:1-HSL. The Alphaproteobacterium also produces N-hexanoyl-HSL (C6-HSL) and N-octanoyl-HSL (C8-HSL) via MsaI.


Subject(s)
4-Butyrolactone/analogs & derivatives , Methylobacterium extorquens/chemistry , Methylobacterium extorquens/metabolism , 4-Butyrolactone/chemistry , 4-Butyrolactone/metabolism , Carbon/metabolism , Gene Expression Regulation, Bacterial , Methanol/metabolism , Methylobacterium extorquens/genetics , Molecular Structure , Succinic Acid/metabolism
4.
Appl Environ Microbiol ; 71(11): 7033-40, 2005 Nov.
Article in English | MEDLINE | ID: mdl-16269739

ABSTRACT

Acidithiobacillus ferrooxidans is one of the main acidophilic chemolithotrophic bacteria involved in the bioleaching of metal sulfide ores. The bacterium-mineral interaction requires the development of biofilms, whose formation is regulated in many microorganisms by type AI-1 quorum sensing. Here, we report the existence and characterization of a functional type AI-1 quorum-sensing system in A. ferrooxidans. This microorganism produced mainly acyl-homoserine lactones (AHL) with medium and large acyl chains and different C-3 substitutions, including 3-hydroxy-C8-AHL, 3-hydroxy-C10-AHL, C12-AHL, 3-oxo-C12-AHL, 3-hydroxy-C12-AHL, C14-AHL, 3-oxo-C14-AHL, 3-hydroxy-C14-AHL, and 3-hydroxy-C16-AHL. A quorum-sensing genetic locus that includes two open reading frames, afeI and afeR, which have opposite orientations and code for proteins with high levels of similarity to members of the acyl synthase (I) and transcriptional regulator (R) protein families, respectively, was identified. Overexpression of AfeI in Escherichia coli and the associated synthesis of AHLs confirmed that AfeI is an AHL synthase. As determined by reverse transcription-PCR, the afeI and afeR genes were transcribed in A. ferrooxidans. The transcription levels of the afeI gene were higher in cells grown in sulfur and thiosulfate media than in iron-grown cells. Phosphate starvation induced an increase in the transcription levels of afeI which correlated with an increase in AHL levels. Two afe boxes which could correspond to the AfeR binding sites were identified upstream of the afeI gene. This is the first report of a functional type AI-1 quorum-sensing system in an acidophilic chemolithotrophic microorganism, and our results provide a very interesting opportunity to explore the control and regulation of biofilm formation during the bioleaching process.


Subject(s)
4-Butyrolactone/analogs & derivatives , Acidithiobacillus/growth & development , Bacterial Proteins/metabolism , Gene Expression Regulation, Bacterial , Ligases/metabolism , 4-Butyrolactone/genetics , 4-Butyrolactone/metabolism , Acidithiobacillus/metabolism , Amino Acid Sequence , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Culture Media , Hydrogen-Ion Concentration , Ligases/chemistry , Ligases/genetics , Models, Molecular , Molecular Sequence Data , Phosphates/metabolism
5.
FEMS Microbiol Lett ; 253(1): 125-31, 2005 Dec 01.
Article in English | MEDLINE | ID: mdl-16239086

ABSTRACT

In Pseudomonas aeruginosa, rhamnolipid production is controlled by the quorum-sensing system RhlRI, which itself depends on LasRI. These systems use cell-to-cell signal molecules: N-butyryl-l-homoserine lactone (C4-HSL) and N-(3-oxododecanoyl)-l-homoserine lactone (3OC(12)-HSL), respectively. Whereas both HSLs were produced in M63 medium, rhamnolipid synthesis was not achieved. Phosphate limitation reduced the HSL concentrations, while allowing rhamnolipid production. Hyperosmotic shock applied during the exponential growth phase stopped the accumulation of 3OC(12)-HSL, and prevented C4-HSL and rhamnolipid production. These defects result from lower expression of genes involved in C4-HSL and rhamnolipid syntheses. The osmoprotectant glycine betaine partially restored C4-HSL and rhamnolipid production.


Subject(s)
Glycolipids/biosynthesis , Pseudomonas aeruginosa/metabolism , 4-Butyrolactone/analogs & derivatives , 4-Butyrolactone/biosynthesis , Base Sequence , Betaine/pharmacology , DNA, Bacterial/genetics , Humans , Kinetics , Osmotic Pressure , Phosphates/metabolism , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/genetics , Pseudomonas aeruginosa/pathogenicity , Signal Transduction , Surface-Active Agents/metabolism
6.
J Chromatogr A ; 1002(1-2): 79-92, 2003 Jun 20.
Article in English | MEDLINE | ID: mdl-12885081

ABSTRACT

A protocol using reversed-phase liquid chromatography coupled with positive-ion electrospray ionization and ion trap mass spectrometry is described for the identification and quantification of N-acylhomoserine lactones (HSLs) in crude cell-free supernatants of bacterial cultures. The HSLs are produced by gram-negative bacteria and act as intercellular signals inducing density-dependent gene expression. Compared with the multi-step procedures previously reported, which included chemical extraction, purification and the use of Escherichia coli HSL biosensors, this on-line LC-MS-MS method is fast and detects 11 HSLs. Its speed and robustness allow the analysis of a large number of samples without loss of performance (no signal variation for a control sample after 90 chromatographic injections). The selectivity is based on the MS-MS fragment ions of the molecular [M+H]- ions and on their relative intensities. For quantification, the m/z 102 ion, specific for the lactone ring and detected with a good signal-to-noise ratio, allows low detection limits even in complex matrix samples (0.28 up to 9.3 pmol). Moreover, this method allows the quantification of 11 HSLs whatever their chemical structure, substituted or not. The protocol was applied to Vibrio vulnificus, a marine bacterium. Six HSLs were detected and quantified with relative standard deviations for repeatability of < 10%.


Subject(s)
Chromatography, High Pressure Liquid/methods , Homocysteine/chemistry , Lactones/analysis , Mass Spectrometry/methods
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