Project description:Ionophores are antibacterial compounds that affect bacterial growth by changing intracellular concentrations of the essential cations, sodium and potassium. They are extensively used in animal husbandry to increase productivity and reduce infectious diseases. Given their widespread usage, it is important to determine the potential negative consequences of ionophore use on human and animal health. In this study, we demonstrate that exposure to the ionophore monensin can select for resistant mutants in the human and animal pathogen Staphylococcus aureus, with a majority of the resistant mutants showing increased growth rates in vitro and/or in mice. Whole-genome sequencing and proteomics analysis of the resistant mutants show that the resistance phenotype is associated with de-repression of de novo purine synthesis, which could be achieved through mutations in different transcriptional regulators including mutations in the gene purR, the repressor of the purine de novo synthesis pathway. This study shows that mutants with reduced susceptibility to the ionophore monensin can be readily selected and highlights an unexplored link between ionophore resistance, purine metabolism and fitness in pathogenic bacteria.
Project description:Genomes and transcriptomes of non-model organisms can be analyzed using next-generation sequencing technologies, but de-novo sequencing and annotating a full eukaryotic genome is still challenging. So, -omics experimentation with non-model organisms requires a suite of technologies to obtain reliable results in a cost-effective manner. Here, a novel method for microarray-based genome analysis is presented which is especially suitable for non-model organisms. We show that it is useful for complementing regular aCGH analyses and for evaluating transcriptome next-generation sequencing reads. The principle of the method is straightforward: feature intensities obtained after hybridizing the test genome are compared with the feature intensities of a control hybridization. The control hybridization is performed with negative control probes (no targets in the control sample), and with positive control probes (with targets in the control sample). The method has in principle a resolution of a single probe and it does not depend on the structural information of a reference genome: the genomic ordering of probe targets is irrelevant. In a test, analyzing the genome content of a sequenced bacterial strain: Staphylococcus aureus MRSA252, this approach proved to be successful demonstrated by receiver operating characteristic area under the curve values larger than 0.9995.
Project description:Genomes and transcriptomes of non-model organisms can be analyzed using next-generation sequencing technologies, but de-novo sequencing and annotating a full eukaryotic genome is still challenging. So, -omics experimentation with non-model organisms requires a suite of technologies to obtain reliable results in a cost-effective manner. Here, a novel method for microarray-based genome analysis is presented which is especially suitable for non-model organisms. We show that it is useful for complementing regular aCGH analyses and for evaluating transcriptome next-generation sequencing reads. The principle of the method is straightforward: feature intensities obtained after hybridizing the test genome are compared with the feature intensities of a control hybridization. The control hybridization is performed with negative control probes (no targets in the control sample), and with positive control probes (with targets in the control sample). The method has in principle a resolution of a single probe and it does not depend on the structural information of a reference genome: the genomic ordering of probe targets is irrelevant. In a test, analyzing the genome content of a sequenced bacterial strain: Staphylococcus aureus MRSA252, this approach proved to be successful demonstrated by receiver operating characteristic area under the curve values larger than 0.9995. DNA from eleven Staphylococcus aureus strains was extracted in three replicates, fragmented, and hybridized onto the S. aureus multistrain microarray. DNA from MRSA252 was used as common reference, but this channel was omitted in further analyses.
Project description:Bacterial transcription factors (TFs) regulate gene expression to adapt to changing environments; when combined, the TF’s regulatory actions comprise transcriptional regulatory networks (TRNs). The chromatin immunoprecipitation (ChIP) assay is the major contemporary method for mapping in vivo protein-DNA interactions in the genome. It enables the genome-wide study of transcription factor binding sites (TFBSs) and gene regulation. Here, we present the genome-wide binding for major TFs in Staphylococcus aureus USA300 strains.
Project description:DNA methylation plays a critical role in development, particularly in repressing retrotransposons. The mammalian methylation landscape is dependent on the combined activities of the canonical maintenance enzyme Dnmt1 and the de novo Dnmts, 3a and 3b. Here we demonstrate that Dnmt1 displays de novo methylation activity in vitro and in vivo with specific retrotransposon targeting. We used whole-genome bisulfite and long-read Nanopore sequencing in genetically engineered methylation depleted embryonic stem cells to provide an in-depth assessment and quantification of this activity. Utilizing additional knockout lines and molecular characterization, we show that Dnmt1's de novo methylation activity depends on Uhrf1 and its genomic recruitment overlaps with targets that enrich for Trim28 and H3K9 trimethylation. Our data demonstrate that Dnmt1 can de novo add and maintain DNA methylation, especially at retrotransposons and that this mechanism may provide additional stability for long-term repression and epigenetic propagation throughout development.
Project description:Treatment of stationary growth phase Staphylococcus aureus SA113 with 100-fold of the MIC of the lipopeptide antibiotic daptomycin leaves alive a small fraction of drug tolerant albeit genetically susceptible bacteria. This study shows that cells of this subpopulation exhibit active metabolism even hours after the onset of the drug challenge. Isotopologue profiling using fully 13C-labeled glucose revealed de novo biosynthesis of the amino acids Ala, Asp, Glu, Ser, Gly and His. The isotopologue composition in Asp and Glu suggested an increased activity of the TCA cycle under daptomycin treatment compared to unaffected stationary growth phase cells. Microarray analysis showed differential expression of specific genes 10 minutes and 3 hours after addition of the drug. Besides factors involved in drug response, a number of metabolic genes appear to shape the signature of daptomycin-tolerant S. aureus cells. These observations will be useful towards the development of new strategies against persisters and related forms of bacterial cells with downshifted physiology.
Project description:Single-molecule read technologies allow for detection of epigenomic base modifications during routine sequencing by analysis of kinetic data during the reaction, including the duration between base incorporations at the elongation site (the "inter-pulse duration.") Methylome data associated with a closed de novo bacterial genome of Salmonella enterica subsp. enterica serovar Javiana str. CFSAN001992 was produced and submitted to the Gene Expression Omnibus. Single-sample sequencing and base modification detection of cultured isolate of a foodborne pathogen.
Project description:Staphylococcus aureus is a major bacterial pathogen that invades and damages host tissue by the expression of devastating toxins. We here performed a phenotypic screen of 35 molecules that were structurally inspired by previous hydroxyamide-based S. aureus virulence inhibitors compiled from commercial sources or designed and synthesized de novo. One of the most potent compounds, AV73, did not only reduce hemolytic alpha-hemolysin expression in S. aureus but also impeded in vitro biofilm formation. The effect of AV73 on bacterial proteomes and extracellular protein levels were analyzed by quantitative proteomics and revealed a significant down-regulation of major virulence and biofilm promoting proteins. To elucidate the mode of action of AV73, target identification was performed using affinity-based protein profiling (AfBPP).
Project description:Primary objectives: The primary objective is to investigate circulating tumor DNA (ctDNA) via deep sequencing for mutation detection and by whole genome sequencing for copy number analyses before start (baseline) with regorafenib and at defined time points during administration of regorafenib for treatment efficacy in colorectal cancer patients in terms of overall survival (OS).
Primary endpoints: circulating tumor DNA (ctDNA) via deep sequencing for mutation detection and by whole genome sequencing for copy number analyses before start (baseline) with regorafenib and at defined time points during administration of regorafenib for treatment efficacy in colorectal cancer patients in terms of overall survival (OS).