N-(3-hydroxyhexanoyl)-l-homoserine lactone is the biologically relevant quormone that regulates the phz operon of Pseudomonas chlororaphis strain 30-84.
Phenazine production by Pseudomonas fluorescens 2-79 and P. chlororaphis isolates 30-84 and PCL1391 is regulated by quorum sensing through the activator PhzR and acyl-homoserine lactones (acyl-HSLs) synthesized by PhzI. PhzI from P. fluorescens 2-79 produces five acyl-HSLs that include four 3-hydroxy species. Of these, N-(3-hydroxyhexanoyl)-HSL is the biologically relevant ligand for PhzR. The quorum-sensing systems of P. chlororaphis strains 30-84 and PCL1391 have been reported to produce and respond to N-(hexanoyl)-HSL. These differences were of interest since PhzI and PhzR of strain 2-79 share almost 90% sequence identity with orthologs from strains 30-84 and PCL1391. In this study, as assessed by thin-layer chromatography, the three strains produce almost identical complements of acyl-HSLs. The major species produced by P. chlororaphis 30-84 were identified by mass spectrometry as 3-OH-acyl-HSLs with chain lengths of 6, 8, and 10 carbons. Heterologous bacteria expressing cloned phzI from strain 30-84 produced the four 3-OH acyl-HSLs in amounts similar to those seen for the wild type. Strain 30-84, but not strain 2-79, also produced N-(butanoyl)-HSL. A second acyl-HSL synthase of strain 30-84, CsaI, is responsible for the synthesis of this short-chain signal. Strain 30-84 accumulated N-(3-OH-hexanoyl)-HSL to the highest levels, more than 100-fold greater than that of N-(hexanoyl)-HSL. In titration assays, PhzR(30-84) responded to both N-(3-OH-hexanoyl)- and N-(hexanoyl)-HSL with equal sensitivities. However, only the 3-OH-hexanoyl signal is produced by strain 30-84 at levels high enough to activate PhzR. We conclude that strains 2-79, 30-84, and PCL1391 use N-(3-OH-hexanoyl)-HSL to activate PhzR.
Khan
Sharik R
SR
Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Herman
Jake
J
Krank
Jessica
J
Serkova
Natalie J
NJ
Churchill
Mair E A
ME
Suga
Hiroaki
H
Farrand
Stephen K
SK
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002853:Chromatography, Liquid; D002855:Chromatography, Thin Layer; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009876:Operon; D010619:Phenazines / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011549:Pseudomonas / Q000235:genetics* / Q000378:metabolism*; D053038:Quorum Sensing; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D053719:Tandem Mass Spectrometry; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D010619:Phenazines; C098602:PhzI protein, Pseudomonas sp.; C088011:PhzR protein, Pseudomonas; D015534:Trans-Activators; C088386:homoserine lactone; D015107:4-Butyrolactone