FT260

“Great fleas have little fleas upon their backs to bite ’em,
And little fleas have lesser fleas, and so ad infinitum.”

So declared Augustus de Morgan, developing a theme by Jonathan Swift in response to naturalists’ ability to find ever-tinier creatures with their new microscopes. A new class of microbe now threatens to upset the rules about how small a living thing can be, as well as splitting the med­ical community on whether they even exist. The microbes in quest­ion are known to their supp­orters as nano­bacteria. Normal bacteria are typically between 0.3 and 5 micrometres (microns or µm) in length; the new discoveries can be as small as 0.02µm.