An unusual, square bacterium that has eluded scientists since its discovery almost 25 years ago has been grown in the lab, by two independent teams. This means researchers can finally investigate the lifestyle and physiology of what is one of the most salt-resistant microbes.

British microbiologist Anthony Walsby first scooped these salty squares out of a hypersaline pond near the Red Sea in 1980. Since then, cultivating “Walsby’s square archaeon” in the lab has been a holy grail for microbiologists studying salt-loving (halophilic) bacteria.

The bacteria are around 0.15 micrometres across and have a remarkable shape, forming wafer-thin, regular tiles. “They look like postage stamps,” says Henk Bolhuis, of the University of Groningen, the Netherlands, who led one of the groups and has an article in the press with Environmental Microbiology.

To study a microbe in the lab, it is essential to be able to cultivate a plentiful supply of pure sample; it would be impractical to regularly collect fresh samples from remote locations. But despite numerous attempts, Walsby’s archaeon has resisted being cultured.

“The assumption has been that it was ungrowable,” says Mike Dyall-Smith, whose team at the University of Melbourne, Australia, is the first to publish a method for cultivation, in the Federation of European Microbiological Societies’ Microbiology Letters.

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