Living Stones

Kidney stones are lumps of insoluble salts congregating in the kidney like sediment on a beach when there isn’t a strong enough current to sluice them out of the body. They can be incredibly painful when they eventually do flush out with urine. Sometimes patients suffer unexplained infections during treatment, and here researchers explore the reason why. They find that the most common type of kidney stone, composed of calcium oxalate, may be alive with bacteria. Captured in a cross section under a high-powered microscope, we see living bacterial biofilms (highlighted in green) among the layers of sedimentary chemicals (red and blue). Further studies reveal bacteria thriving in the urine-rich environment of the kidney may help the salts to clump together – all the more reason to stay hydrated.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Image from work by William C. Schmidt and Ava Mousavi, and colleagues
• Department of Bioengineering and Department of Urology, University of California Los Angeles, CA, USA
• Video originally published with a Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0)
• Published in Proceedings of the National Academy of Science (PNAS), January 2026