Building ’nanomachines’ in biological outer space

It's exciting how economical bacteria are, able to harness the thermal free energy from unfolded subunits and convert it into a coherent directed transport - Dr Lewis Evans Cambridge scientists have uncovered the mechanism by which bacteria build their surface propellers (flagella) - the long extensions that allow them to swim towards food and away from danger. The results, published this week , demonstrate how the mechanism is powered by the subunits themselves as they link in a chain that is pulled to the flagellum tip. Previously, scientists thought that the building blocks for flagella were either pushed or diffused from the flagellum base through a central channel in the structure to assemble at the flagellum tip, which is located far outside the cell. However, these theories are incompatible with recent research showing that flagella grow at a constant rate. The completely new and unexpected chain mechanism, in which subunits linked in a chain 'pull themselves' through the flagellum, transforms understanding of how flagellum assembly is energised. Dr Lewis Evans, who carried out the research, remarked: "It's exciting how economical bacteria are, able to harness the thermal free energy from unfolded subunits and convert it into a coherent directed transport. More broadly, it's fascinating to imagine the implications for how heat energy (normally considered as 'lost') might be harnessed to drive processes even outside living cells." As each flagellum 'nanomachine' is assembled, thousands of subunit 'building blocks' are made in the cell and are then unfolded and exported across the cell membrane.