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Inside a bacterial cell's 'crisis command centre'

EU-funded scientists have shed new light on bacterial 'crisis command centres', giant molecules that help bacteria mount a rapid response to a wide range of stresses and dangers. The findings, which are published in the latest edition of the journal Science, increase our under...

EU-funded scientists have shed new light on bacterial 'crisis command centres', giant molecules that help bacteria mount a rapid response to a wide range of stresses and dangers. The findings, which are published in the latest edition of the journal Science, increase our understanding of how bacteria survive in harsh, changing environments. At the heart of the bacterial stress management system is a large molecule called a 'stressosome'. The bacteria investigated in this study were found to have around 20 of these structures dotted fairly evenly around the inside of the cell. Stressosomes are able to respond quickly to a wide range of environmental factors, including changes in light, temperature or salinity, and trigger a response designed to ensure the cell's survival. However, until now the mechanisms behind this process were unknown. In this latest piece of research, the scientists drew on cutting-edge imaging techniques and used the UK's Diamond synchrotron light source in their quest to get to the heart of the stressosome. This enabled them to view the activity of individual proteins in the stressosome. When the external environment changes in a way that could be harmful to the bacteria, a warning signal is sent from the cell surface to the cell's interior. As soon as the stressosomes detect the warning signal, a number of proteins called RSBTs break away from the structure. This in turn triggers a chain of reactions which result in the production of over 150 new proteins that help the cell adapt to and survive in its new environment. 'The cascade of events inside bacteria cells that occurs as a result of stressosomes receiving warning signals leads to particular genes inside (the) cell being transcribed more,' explains Professor Marin van Heel of Imperial College London, UK. 'This means that some genes already active inside the cell are 'turned up' so that levels of particular proteins in the cell increase. These changes to the protein make-up of the cell enable it to survive in a hostile or challenging environment.' 'The cell's stressosomes are very good at their job as crisis command centres because they provide a very fast, effective response to danger,' adds Dr Tim Grant, also of Imperial College London. 'The chain reaction they kick start, produces results really quickly, which enables bacteria to adapt to changes in their surroundings almost instantaneously.' The team is now keen to use even more advanced imaging techniques to probe more deeply into the workings of the stressosome. They hope that by using the new high-resolution cryo-electron microscope at the Max Planck Institute in Martinsried, Germany, they will be able to see the individual building blocks of the proteins that make up the stressosome. EU support for the research came from the 3DEM ('Three-dimensional electron microscopy') project, which is financed through the 'Life sciences, genomics and biotechnology for health' Thematic area of the Sixth Framework Programme (FP6).