Two species of bacteria were used in the experiment, both genetically modified to produce fluorescent light for easier observation.

The rod-shaped bacteria used their normal mode of movement even in channels only 30 percent wider than their own diameter. But when the slits were even smaller, the microbes changed their tactics and started squeezing through, remarkably changing their shape. E. coli bacteria managed to pass narrow slits that were only half their own diameter in width.

“This took us totally by surprise. The bacteria become completely flattened. They have all sorts of peculiar shapes both in the channels and when they finally come out at the other side,” says post-doctoral researcher Jaan Männik.

What’s more interesting is that even in extreme confinement the bacteria grew and divided at normal speeds. And the processes were crucial for their passing through the channels.

The results of the study, which was published in the journal Proceedings of the National Academy of Sciences, may change the estimates of the biomass of bacteria living underground in spaces measuring around a micrometer. There may also be implications for water filters and medial applications.