Project description:Acyl-homoserine lactone (acyl-HSL) quorum sensing was first discovered in Vibrio fischeri where it serves as a key control element of the seven-gene luminescence (lux) operon. Since this initial discovery, other bacteria have been shown to control hundreds of genes by acyl-HSL quorum sensing. Until recently, it has been difficult to examine the global nature of quorum sensing in V. fischeri. However, the complete genome sequence of V. fischeri is now available and this has enabled us to use transcriptomics to identify quorum-sensing regulated genes and to study the quorum-controlled regulon of this bacterium. In this study, we used DNA microarray technology to identify over two-dozen V. fischeri genes regulated by the quorum sensing signal N-3-oxohexanoyl-L-homoserine lactone (3OC6-HSL). Keywords: Comparison of transcriptome profiles
Project description:Many Gram-negative bacteria employ cell-to-cell communication mediated by N-acyl homoserine lactones (quorum sensing) to control expression of a wide range of genes including, but not limited to, genes encoding virulence factors. Outside the laboratory, the bacteria live in complex communities where signals may be perceived across species. We here present a newly found natural quorum sensing inhibitor, produced by the pseudomonads Pseudomonas sp. B13 and Pseudomonas reinekei MT1 as a blind end in the biodegradation of organochloride xenobiotics, which inhibits quorum sensing in P. aeruginosa in naturally occurring concentrations. This catabolite, 4-methylenebut-2-en-4-olide, also known as protoanemonin, has been reported to possess antibacterial properties, but seems to have dual functions. Using transcriptomics and proteomics, we found that protoanemonin significantly reduced expression of genes and secretion of proteins known to be under control of quorum sensing in P. aeruginosa. Moreover, we found activation of genes and gene products involved in iron starvation response. It is thus likely that inhibition of quorum sensing, as the production of antibiotics, is a phenomenon found in complex bacterial communities.
Project description:Paenibacillus polymyxa is an agriculturally important plant growth promoting rhizobacterium (PGPR). Many Paenibacillus species are known to be engaged in complex bacteria-bacteria and bacteria-host interactions, which in other bacteria were shown to necessitate quorum sensing communication, but to date no quorum sensing systems have been described in Paenibacillus. Here we show that the type strain P. polymyxa ATCC 842 encodes at least 16 peptide-based communication systems. Each of these systems comprises a pro-peptide that is secreted to the growth medium and further processed to generate a mature short peptide. Each peptide has a cognate intracellular receptor of the RRNPP family, and we show that external addition of P. polymyxa communication peptides to the medium leads to reprogramming of the transcriptional response. We found that these quorum sensing systems are conserved across hundreds of species belonging to the Paenibacillaceae family, with some species encoding more than 25 different peptide-receptor pairs, representing a record number of quorum sensing systems encoded in a single genome.
Project description:Many Gram-negative bacteria employ cell-to-cell communication mediated by N-acyl homoserine lactones (quorum sensing) to control expression of a wide range of genes including, but not limited to, genes encoding virulence factors. Outside the laboratory, the bacteria live in complex communities where signals may be perceived across species. We here present a newly found natural quorum sensing inhibitor, produced by the pseudomonads Pseudomonas sp. B13 and Pseudomonas reinekei MT1 as a blind end in the biodegradation of organochloride xenobiotics, which inhibits quorum sensing in P.M-bM-^@M-^Caeruginosa in naturally occurring concentrations. This catabolite, 4-methylenebut-2-en-4-olide, also known as protoanemonin, has been reported to possess antibacterial properties, but seems to have dual functions. Using transcriptomics and proteomics, we found that protoanemonin significantly reduced expression of genes and secretion of proteins known to be under control of quorum sensing in P.M-bM-^@M-^Caeruginosa. Moreover, we found activation of genes and gene products involved in iron starvation response. It is thus likely that inhibition of quorum sensing, as the production of antibiotics, is a phenomenon found in complex bacterial communities. Strain P. aeruginosa MPAO1 was cultivated under defined ABT medium. The orginal culture was divided in the early exponential phase into two parts. One was treated with 125M-NM-<M Protoanemonin and the other served as a control. The experiment was performed in duplicates.
Project description:FliA in S. Typhimurium directs transcription of large numbers of unstable, non-coding RNAs from intragenic promoters. Also in this study, we identify two previously unreported FliA-transcribed protein coding genes, including sdiA, which encodes a transcription factor that responds to quorum sensing signals produced by other bacteria.
Project description:Quorum sensing is a term used to describe cell-to-cell communication that allows cell density-dependent gene expression. Many Gram-negative bacteria use acyl-homoserine lactone (acyl-HSL) synthases to generate fatty acyl-HSL quorum sensing signals, which function with signal receptors to control expression of specific genes. The fatty acyl group is derived from fatty acid biosynthesis and provides signal specificity, but the variety of signals is limited. We have discovered that the photosynthetic bacterium Rhodopseudomonas palustris uses an acyl-HSL synthase to produce p-coumaroyl-HSL by using environmental p-coumaric acid rather than fatty acids from cellular pools. The bacterium has a signal receptor with homology to fatty acyl-HSL receptors that responds to p-coumaroyl-HSL to regulate global gene expression. We also found that p-coumaroyl-HSL is made by other bacteria including Bradyrhizobium BTAi1 and Silicibacter pomeroyi DSS-3. This discovery extends the range of possibilities for acyl-HSL quorum sensing and raises fundamental questions about quorum sensing within the context of environmental signaling. Keywords: Comparison of transcriptome profiles Transcriptome profiles between Rhodopseudomonas palustris cells grown in the in the presence or absence of pC-HSL were compared.
Project description:Quorum sensing is a term used to describe cell-to-cell communication that allows cell density-dependent gene expression. Many Gram-negative bacteria use acyl-homoserine lactone (acyl-HSL) synthases to generate fatty acyl-HSL quorum sensing signals, which function with signal receptors to control expression of specific genes. The fatty acyl group is derived from fatty acid biosynthesis and provides signal specificity, but the variety of signals is limited. We have discovered that the photosynthetic bacterium Rhodopseudomonas palustris uses an acyl-HSL synthase to produce p-coumaroyl-HSL by using environmental p-coumaric acid rather than fatty acids from cellular pools. The bacterium has a signal receptor with homology to fatty acyl-HSL receptors that responds to p-coumaroyl-HSL to regulate global gene expression. We also found that p-coumaroyl-HSL is made by other bacteria including Bradyrhizobium BTAi1 and Silicibacter pomeroyi DSS-3. This discovery extends the range of possibilities for acyl-HSL quorum sensing and raises fundamental questions about quorum sensing within the context of environmental signaling. Keywords: Comparison of transcriptome profiles
Project description:Microarray data for study "The master regulators AphA and LuxR control the Vibrio harveyi quorum-sensing regulon: analysis of their individual and combined effects". Bacteria use a chemical communication process called quorum sensing to control transitions between individual and group behaviors. In the Vibrio harveyi quorum-sensing circuit, two master transcription factors AphA and LuxR coordinate the quorum-sensing response. Here we show that AphA regulates 167 genes, LuxR regulates 625 genes, and they co-regulate 77 genes. LuxR strongly controls genes both at low-cell-density and high-cell-density, suggesting it is the major quorum-sensing regulator. By contrast, AphA is absent at high-cell-density, and acts to fine-tune quorum-sensing gene expression at low-cell-density. We examined two loci as case studies of co-regulation by AphA and LuxR. First, AphA and LuxR directly regulate expression of the genes encoding the quorum regulatory small RNAs Qrr2, Qrr3, and Qrr4, the consequence of which is a specifically timed transition between the individual and the group lifestyle. Second, AphA and LuxR repress type III secretion system genes but at different times and to different extents. The consequence of this regulation is that type III secretion is restricted to a peak at mid-cell-density. Thus, asymmetric production of AphA and LuxR coupled with differences in their strength and timing of target gene regulation generates a precise temporal pattern of gene expression.