Bacteria are evenly matched in swimming contests, no matter their size

Dedicated fans of the Olympics know many tall athletes swim faster because their long limbs churn more water with each stroke. But a new study published in the Proceedings of the National Academy of Sciences shows that for bacteria, body sizes don’t affect their swimming speeds , settling a long debate in the field. Bacteria, big and small, use their tiny, lashlike limbs to travel. These minipropellers, called flagella, are their lifelines. They thrust the cells toward essential food sources and help them escape deadly threats. Intuitively, longer cells should encounter more resistance in a fluid, hence slowing their pace. To test this, scientists tracked the “tumble-and-run” motions of more than 25,000 Escherichia coli cells (pictured) with high-resolution scans every 0.1 millisecond. There were no clear victors: All the bacteria, ranging from 2 to 6 microns long, swam almost exactly 20 microns per second. Each little whip spins about 100 times per second to help propel the hefty cells. To keep up with their shorter kin, the researchers found, longer bacteria grow a greater number of flagella and disperse their swimming loads among these bundles of limbs. This ability to swim at a synchronous pace allows bigger cells to stay with their pack when traversing viscous fluids to form colonies that increase their chances of survival. The results may help scientists understand how microbes spread infection, the researchers say....
Source: ScienceNOW - Category: Science Source Type: news