Project description:Here we report the results of a study comparing the global transcriptional responses of Escherichia coli to two well-studied CAMPs, LL37 and colistin, and two ceragenins with related structures, CSA13 and CSA131. We found that E. coli responds similarly to both CAMPs and ceragenins by inducing a Cpx envelope stress response. However, whereas E. coli exposed to CAMPs increased expression of genes involved in colanic acid biosynthesis, bacteria exposed to ceragenins specifically modulated functions related to phosphate transport, indicating distinct mechanisms of action between these two classes of molecules. Overall, this study suggests that while some bacterial responses to ceragenins overlap with those induced by naturally-occurring CAMPs, these synthetic molecules target the bacterial envelope using a distinctive mode of action.
Project description:Transcriptional profiling of Escherichia coli in the biofilm mode of growth. A comparison of the transcriptional profiles of the biofilm interior and perimeter.
Project description:Obtaining an in depth understanding of the arms races between peptides comprising the innate immune response and bacterial pathogens is of fundamental interest and will inform the development of new antibacterial therapeutics. Many cationic antimicrobial peptides (AMPs) share a range of structural and physical features that have been linked to antibacterial activity and yet they vary dramatically in their potency towards the same bacterial target. We hypothesised that a whole organism view of AMP challenge on Escherichia coli could provide a sophisticated, bacterial perspective enabling understanding of how potency is linked to mode of action. We used a 1H NMR metabolomic approach to characterise the effect on E. coli of challenge with four structurally and physically related AMPs: magainin 2, pleurocidin, buforin II and a designed peptide comprising D-amino acids only. Sub-inhibitory conditions, where these peptides nevertheless induced a bacterial response, were identified enabling electron microscopic and transcriptomic analyses. Although some common features of the bacterial response to AMP challenge could be identified, the metabolomes, morphological changes and the vast majority of the changes in gene expression were specific to each AMP. We show the antibacterial mode of action of AMPs can be accurately predicted by comparing ontological profiles generated by transcriptomic analyses. The response of E. coli to AMP challenge is highly plastic, with the bacteria capable of deploying a multifaceted response adapted to the mode of action rather than the physical properties of the AMP.
Project description:Antibiotics of the orthosomycin class bind at a distinct site on the large subunit of the bacterial ribosome not used by any other known protein synthesis inhibitor. Structural and biochemical in vitro studies suggested that orthosomycins should block accommodation of aminoacyl-tRNAs in the ribosomal A-site arresting the ribosome at the start codons of the genes. However, the mode of action of orthosomycins in the living cell remains unknown. Here, to get a general and unbiased view of the mode of action of orthosomycin antibiotics, we carried out genome-wide ribosome profiling analysis in Escherichia coli cells exposed to evernimicin, one of the most active antibiotics of this class. Our in vivo data, supported by the analysis of evernimicin action upon in vitro translation of a variety of mRNAs, argue that orthosomycins preferentially inhibit translation elongation and act in a context specific manner. We show that evernimicin predominantly arrests translation when the ribosome needs to accommodate Pro-tRNA or Leu-tRNA in the A site while polymerizing specific amino acid sequences. We further show that the discovered context specificity of orthosomycins is exploited for the programmed translation arrest that apparently regulates resistance to these antibiotics.
Project description:We recently reported that carbon monoxide (CO) has bactericidal activity. To understand its mode of action we analysed the gene expression changes occurring when Escherichia coli, grown aerobically and anaerobically, is treated with the carbon monoxide releasing molecule, CORM-2. The E. coli microarray analysis shows that E. coli CORM-2 response is multifaceted with a high number of differentially regulated genes spread through several functional categories, namely genes involved in inorganic ion transport and metabolism, regulators, and genes implicated in posttranslational modification, such as chaperones. CORM-2 has higher impact in E. coli cells grown anaerobically, as judged by the existence of repressed genes belonging to eight functional classes which are absent in aerobically CORM-2 treated cells. In spite of the relatively stable nature of the CO molecule, our results show that CO is able to trigger a significant alteration in the transcriptome of E. coli which necessarily has effects in several key metabolic pathways.
Project description:Primary objectives: The study investigates whether a Escherichia coli Nissle-suspenison has a (preventive) antidiarrheal effect in patients with tumors who are treated with chemotherapeutic schemes which are associated with increased occurances of diarrhea. Diarrhea caused by treatment are thought to be reduced in intensity and/or frequency by the treatment with Escherichia coli Nissle-Suspension.
Primary endpoints: Common toxicity criteria (CTC) for diarrhea
Project description:The purpose of this study is to determine whether the presence of pathogenic Escherichia coli in colon is associated with psychiatric disorders.
Project description:To demonstrate plasmid transferability by conjugation, cultures of the donor S. Infantis, and recipient Escherichia coli (E. coli) K12 were mated. S. Infantis and transconjugant were screened for resistance genes.
Project description:We find that the response regulator TorR protein of the TorR/TorS two-component signal transduction system localizes to the old poles of the Escherichia coli cells, forming a functional focus. Interestingly, TorR co-localizes with the nucleoid in a cell-cycle-dependent mode, implying a cell-cycle-dependent interaction of TorR with its target genes.
