In this respect, E. coli is a model bacterium to study the continuum between commensal and pathogenic bacteria. Researchers at INRA in Toulouse, in collaboration with German universities in Würzburg and Göttingen and the Institut Pasteur in Paris, have shown for the first time that both commensal and pathogenic E. coli produce a substance which is toxic to the DNA in eukaryotic cells. The bacteria producing this toxin thus induce DNA breaks in host cells and disturb the cell cycle. This slowdown of eukaryotic cell proliferation may enhance bacterial colonization of the intestine. On the other hand, if these breaks are not repaired, they could give rise to a high level of mutations, which are the principal factors triggering cancer in man. The details of this work have been published in Science, August 11th 2006.
Colibactin, a new toxin which affects the host cell cycle
Certain strains of E. coli produce a toxin, which induces a toxic effect in host cells, characterised by gradual cell enlargement following the arrest of cell proliferation. INRA researchers in Toulouse, in collaboration with teams at the German universities of Würzburg and Göttingen and the Institut Pasteur in Paris, have demonstrated that these bacterial strains possess a "genomic island" in their genome, which contains all genes allowing the biosynthesis of a new toxin, which they have called "Colibactin". The researchers have shown that the bacteria producing this toxin induce serious lesions to the DNA of host cells, causing a blockade of the cell cycle of infected cells. Colibactin belongs to a new family of bacterial toxins, which are able to act on the cell cycle of eukaryotic cells. The INRA researchers have proposed to call this family the "cyclomodulins".
Colibactin is a non-protein toxin. The genes carried by the genomic island code for several enzymes belonging to the family of "polyketide synthetases" (PKS) and "nonribosomal polypeptide synthetases" (NRPS). Compounds arising from these biosynthetic pathways constitute a large family of natural products with a very broad range of biological activities and pharmacological properties. This family comprises numerous molecules which are of importance both agronomically (anti-parasite substances, such as avermectin) and medically (e.g. immunosuppressants, cholesterol-lowering agents, anticancer compounds and antibiotics (cyclosporine, lovastatin, bleomycin, erythromycin, etc.). This is the first time that an enzyme system of this type, producing a molecule active on eukaryote cells, has been characterised in E. coli, a bacterial species where genetic engineering is well mastered. This discovery provides a biotechnological key to producing new compounds of interest, and has been the subject of a patent application. It opens the way to novel therapeutic approaches as well as preventive opportunities.
Infectious diseases, cancer and anti-proliferative effects: is there a role for bacteria producing cyclomodulins?
The work reported in Science also raises an important question for public health. DNA double strand breaks are dangerous lesions affecting eukaryotic cells; if these are not repaired, they give rise to a high level of mutations, which are the principal triggers of cancer in man. Colibactin is produced by both commensal E. coli in the intestinal flora and pathogenic strains which are responsible for septicaemia, urinary tract infections and meningitis. The presence of these bacteria in the commensal flora may therefore constitute a predisposing factor for the development of certain cancers. Thus bacterial flora may participate in the development, differentiation and homeostasis of mucosa and hence the development of certain types of cancer, or protection against them.
Céline Goupil | alfa
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy