title: Identification and characterization of a GDSL esterase gene located proximal to the swr quorum-sensing system of Serratia liquefaciens MG1.
abstract: Serratia liquefaciens MG1 employs the swr quorum-sensing system to control various functions, including production of extracellular enzymes and swarming motility. Here we report the sequencing of the swr flanking DNA regions. We identified a gene upstream of swrR and transcribed in the same direction, designated estA, which encodes an esterase that belongs to family II of lipolytic enzymes. EstA was heterologously expressed in Escherichia coli, and the substrate specificity of the enzyme was determined in crude extracts. With the aid of zymograms visualizing EstA on polyacrylamide gels and by the analysis of a transcriptional fusion of the estA promoter to the promoterless luxAB genes, we showed that expression of the esterase is not regulated by the swr quorum-sensing system. An estA mutant was generated and was found to exhibit growth defects on minimal medium containing Tween 20 or Tween 80 as the sole carbon source. Moreover, we show that the mutant produces greatly reduced amounts of N-acyl-homoserine lactone (AHL) signal molecules on Tween-containing medium compared with the wild type, suggesting that under certain growth conditions EstA may be important for providing the cell with precursors required for AHL biosynthesis.
authors.affiliation: Department of Microbiology, Technical University Munich, Am Hochanger 4, D-85350 Freising, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Riedel
authors.forename: Daniela
authors.initials: D
authors.lastname: Talker-Huiber
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Helmut
authors.initials: H
authors.lastname: Schwab
authors.forename: Leo
authors.initials: L
authors.lastname: Eberl
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D004950:Esterases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012705:Serratia / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D015398:Signal Transduction; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004950:Esterases