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:Antimicrobial peptides (AMPs) are promising alternatives to classical antibiotics against antibiotic-resistant pathogens. TAT-RasGAP (317-326) is an AMP with broad range antibacterial activity, but its mechanism of action is unknown. Escherichia coli can become partially resistant to TAT-RasGAP (317-326) in vitro. In this study, we analysed a strain of E. coli with extensive resistance to TAT-RasGAP (317-326) but not to other AMPs that we obtained after twenty passages during an in vitro resistance selection experiment. This strain accumulates four mutations, that all apparently affect bacterial envelope composition. One of these mutations is a point mutation in bamA, which encodes an essential protein involved in the folding and proper insertion of outer membrane proteins. The point mutation resulted in a charge change in an area of the protein corresponding to a negatively charged loop at the surface of BamA. Using CRISPR-Cas9-based targeted mutagenesis, we showed that mutations lowering the negative charge of this loop decreased sensitivity of E. coli to TAT-RasGAP (317-326). In silico simulations unveiled the molecular driving forces responsible for the interaction between TAT-RasGAP (317-326) and BamA. These results indicated that electrostatic interactions, particularly hydrogen bonds, are involved in the stability of the molecular complex, representing a predictive fingerprint of the TAT-RasGAP (317-326) - BamA interaction strength. Interestingly, BamA activity was not affected by TAT-RasGAP (317-326), indicating that BamA may function as a specific receptor for this AMP. Our results indicate that binding and entry of TAT-RasGAP (317-326) may involve different mechanisms compared to other AMPs, which is in line with limited cross-resistance observed between different AMPs. This limited cross-resistance is important for the clinical application of AMPs towards drug-resistant pathogens.
Project description:Despite the characterization of many aetiologic genetic changes. The specific causative factors in the development of sporadic colorectal cancer remain unclear. This study was performed to detect the possible role of Enteropathogenic Escherichia coli (EPEC) in developing colorectal carcinoma.
Project description:Antimicrobial peptides (AMPs) are promising alternatives to classical antibiotics against multidrug resistant pathogens. TAT-RasGAP (317-326) is an AMP with broad range antibacterial activity, but its mechanism of action is unknown. Escherichia coli can become partially resistant to TAT-RasGAP (317-326) in vitro when passaged eight times with increasing concentrations of this peptide via mutations of the two-component system EnvZ/OmpR. To test whether additional mutations can cause further increase in resistance, we analysed a strain of E. coli showing high level of specific resistance to TAT-RasGAP (317-326) that we obtained after twenty passages of in vitro resistance selection. This strain bears, in addition to an envZ point mutation, a point mutation in bamA, an essential gene encoding an insertase involved in the insertion of outer membrane proteins. This mutation modifies the charge in a negatively charged loop (Q495-T505) at the surface of BamA. In silico docking simulations predict that binding affinity between TAT-RasGAP (317-326) and BamA varies depending on the charge of the Q495-T505 loop. We show here using CRISPR-Cas9-based targeted mutagenesis that mutations lowering the negative charge of the Q495-T505 loop decrease sensitivity of E. coli to TAT-RasGAP (317-326). Interestingly, BamA activity was not affected by TAT-RasGAP (317-326), indicating that BamA may function as a specific receptor for the AMP TAT-RasGAP (317-326). Our results indicate that binding and entry of TAT-RasGAP (317-326) may involve different mechanisms compared to other AMPs, which is in line with limited cross-resistance observed between different AMPs. This limited cross-resistance is important for the clinical application of AMPs towards multidrug resistant pathogens.
