Project description:Indole is ubiquitously synthesized by plants and bacteria and functions as an inter species signaling molecule to modulate a wide variety of cellular activities. However, it is not clear how the indole signal is perceived and responded by plant growth promoting rhizobacteria (PGPR) at the rhizosphere. Here, we demonstrated that indole enhanced antibiotic tolerance of Pseudomonas fluorescens 2P24, a PGPR well known for its biocontrol capacity. By conducting quantitative proteomic analysis, we showed that indole influences the expression of multiple genes including the emhABC operon encoding the major multidrug efflux pump in P. fluorescens 2P24. The indole-induced antibiotic tolerance was not related to bacterial dormancy or slow growth, but depended on the emhABC operon and the divergently transcribed TetR-like regulator emhR. By binding to the semi-palindromic operator sequence, EmhR repressed the expression of emhABC. It was further revealed that indole bound to EmhR and weakened the interaction between EmhR and the operator. This is consistent with our finding that indole-induced expression of the EmhABC efflux pump is dependent on EmhR. Using homology modeling and molecular dynamics simulation, we found that indole binding resulted in significantly decreased distance between the two DNA-recognizing α3 helices within the EmhR dimer, which would possibly account for its compromised DNA binding capacity. EmhR was further shown to globally influence protein expressions, especially transporters and proteins involved in the denitrification pathway. This EmhR-dependent, indole-induced antibiotic tolerance is likely to be prevalent in the Pseudomonas species, as the EmhR homologue in Pseudomonas syringae was also shown to be responsible for the indole-induced antibiotic tolerance. Taken together, our results revealed an indole-sensing transcription factor EmhR responsible for indole-induced antibiotic tolerance in Pseudomonas species and have important implications on the general mechanism for the indole sensing and responses in rhizobacteria.
Project description:Pseudomonas species are ubiquitous in plant-associated environments and produce an array of volatiles, enzymes and antimicrobials. The biosynthesis of many metabolites is regulated by the GacS/GacA two-component regulatory system. Transcriptome analysis of Pseudomonas fluorescens SBW25 revealed that 702 genes were differentially regulated (fold change>4, P<0.0001) in a gacS::Tn5 mutant, with 300 and 402 genes up- and down-regulated, respectively. Genes that were significantly down-regulated are involved in viscosin biosynthesis (viscABC), protease production (aprA), motility, biofilm formation, and secretory systems. Genes that were significantly up-regulated are involved in siderophore biosynthesis and oxidative stress. In contrast to previous studies with gac-mutants of other Pseudomonas species/strains, the gacS mutant of SBW25 inhibited growth of oomycete, fungal and bacterial pathogens significantly more than parental strain SBW25. A potential candidate for this enhanced antimicrobial activity was a large nonribosomal peptide synthetase (NRPS) gene cluster predicted to encode for an 8-amino-acid ornicorrugatin-like peptide. Site-directed mutagenesis of an NRPS gene in this cluster, however, did not lead to a reduction in the antimicrobial activity of the gacS mutant. Collectively these results indicate that a mutation in the GacS/GacA regulatory system causes major transcriptional changes in P. fluorescens SBW25 and significantly enhances its antimicrobial activities by yet unknown mechanisms. This expression study used total RNA recovered from four separate wild-type cultures of Pseudomonas fluorescens SBW25 and four separate cultures of the gacS mutant. Expression design was based on the updated genome sequence of Pseudomonas fluorescens SBW25, NC_012660.1 and associated plasmid pQBR0476 with nineteen 60-mer probe per gene. Each probe is replicated 3 times. The design includes random GC and other control probes.
Project description:The goal of this study was to evaluate the molecular mechanisms by which Brachypodium distachyon grown with and without Pseudomonas fluorescens (P. fluorescens) strain SBW25 respond to Fe deprivation. Fe deprivation induced Brachypodium secretion of phytosiderophores and reduced biomass production while inoculation with P. fluorescens resulted in alterations of extracellular metabolite abundances. Results provide insight into the role of iron in interactions between a host plant and root associated bacteria.
Project description:Hfq is a transcriptional and translational pleiotropic regulator in several bacteria. RNA-Seq, Ribo-Seq and Proteomic analyses were carried out in the wild-type and a hfq deletion strain of Pseudomonas fluorescens SBW25 with the intention to separate the influence of Hfq on the transcript stability and translation. This submission relates to the RNA-Seq data only. RNA was extracted from two replicate cultures each of SBW25-WT and SBW25-Δhfq strains and, after removal of ribosomal RNA, subjected to RNA-Seq in an Illumina NextSeq500 machine. The resulting sequence data was analysed by mapping to the reference sequence of Pseudomonas fluorescens SBW25 as available in the Genbank accession NC_012660.
Project description:Pseudomonas fluorescens strain SS101 (Pf.SS101) promotes growth of Arabidopsis thaliana, enhances greening and lateral root formation, and induces systemic resistance (ISR) against the bacterial pathogen Pseudomonas syringae pv. tomato (Pst). Here, targeted and untargeted approaches were adopted to identify bacterial determinants and underlying mechanisms involved in plant growth promotion and ISR by Pf.SS101. Based on targeted analyses, no evidence was found for volatiles, lipopeptides and siderophores in plant growth promotion by Pf.SS101. Untargeted, genome-wide analyses of 7,488 random transposon mutants of Pf.SS101 led to the identification of 21 mutants defective in both plant growth promotion and ISR. Many of these mutants, however, were auxotrophic and impaired in root colonization. Genetic analysis of three mutants followed by site-directed mutagenesis, genetic complementation and plant bioassays revealed the involvement of the phosphogluconate dehydratase gene edd, the response regulator gene colR and the adenylsulfate reductase gene cysH in both plant growth promotion and ISR. Subsequent comparative plant transcriptomics analyses strongly suggest that modulation of sulfur assimilation, auxin biosynthesis and transport, steroid biosynthesis and carbohydrate metabolism in Arabidopsis are key mechanisms linked to growth promotion and ISR by Pf.SS101. Comparative transcriptome analysis of Arabidopsis treated with Pf. SS101, a growth and ISR promoting rhizobacteria and plants treated with cysH mutant of Pf.SS101 that fails to induce the afformentioned phenotypes
Project description:Hfq is a transcriptional and translational pleiotropic regulator in several bacteria. RNA-Seq, Ribo-Seq and Proteomic analyses were carried out in the wild-type and a hfq deletion strain of Pseudomonas fluorescens SBW25 with the intention to separate the influence of Hfq on the transcript stability and translation. This submission relates to the Ribosome profiling data only. Ribosomes were purified from MNase treated cell lysates by density gradient ultracentrifugation from two replicate cultures each of SBW25-WT and SBW25-hfq strains. RNA was extracted from the purified ribosomes and subjected to RNA-Seq in an Illumina HiSeq2000 machine. The resulting sequence data was analysed by mapping to the reference sequence of Pseudomonas fluorescens SBW25 as available in the Genbank accession NC_012660.
Project description:Pseudomonas species are ubiquitous in plant-associated environments and produce an array of volatiles, enzymes and antimicrobials. The biosynthesis of many metabolites is regulated by the GacS/GacA two-component regulatory system. Transcriptome analysis of Pseudomonas fluorescens SBW25 revealed that 702 genes were differentially regulated (fold change>4, P<0.0001) in a gacS::Tn5 mutant, with 300 and 402 genes up- and down-regulated, respectively. Genes that were significantly down-regulated are involved in viscosin biosynthesis (viscABC), protease production (aprA), motility, biofilm formation, and secretory systems. Genes that were significantly up-regulated are involved in siderophore biosynthesis and oxidative stress. In contrast to previous studies with gac-mutants of other Pseudomonas species/strains, the gacS mutant of SBW25 inhibited growth of oomycete, fungal and bacterial pathogens significantly more than parental strain SBW25. A potential candidate for this enhanced antimicrobial activity was a large nonribosomal peptide synthetase (NRPS) gene cluster predicted to encode for an 8-amino-acid ornicorrugatin-like peptide. Site-directed mutagenesis of an NRPS gene in this cluster, however, did not lead to a reduction in the antimicrobial activity of the gacS mutant. Collectively these results indicate that a mutation in the GacS/GacA regulatory system causes major transcriptional changes in P. fluorescens SBW25 and significantly enhances its antimicrobial activities by yet unknown mechanisms.
Project description:This SuperSeries is composed of the following subset Series: GSE29319: Iron-starvation effect on transcriptome of Pseudomonas fluorescens Pf-5: iron(II) chloride GSE29320: Iron-starvation effect on transcriptome of Pseudomonas fluorescens Pf-5: iron(III) chloride Refer to individual Series
Project description:This SuperSeries is composed of the following subset Series: GSE33907: Tannic acid (20 µg/ mL) treatment effect on transcriptome of Pseudomonas fluorescens Pf-5 GSE33908: Tannic acid (160 µg/ mL) treatment effect on transcriptome of Pseudomonas fluorescens Pf-5 Refer to individual Series
Project description:HutC in Pseudomonas is a representative member of the HutC/GntR family of transcriptional regulators, which possess a N-terminal winged helix-turn-helix (wHTH) DNA-binding domain and a C-terminal substrate binding domain. HutC is generally known to represses expression of histidine utilization (hut) genes through binding to the PhutU promoter with urocanate (the first intermediate of the histidine degradation pathway) as the direct inducer. Here we first describe the detailed molecular interactions between HutC and its PhutU target site in a plant growth promoting bacterium P. fluorescens SBW25, and further show that HutC possesses specific DNA-binding activities with many targets in SBW25 genome. Subsequent RNA-seq analysis and phenotypic assays revealed an unexpected global regulatory role of HutC for successful bacterial colonization in planta.