Growing the ungrowable

SAR11 and related ribosomal RNA genes exist in nearly every pelagic marine bacterioplankton community but the cultivation of the microorganisms that carry these genes have failed in the past. In August 8 Nature, Michael Rappe and colleagues at Oregon State University, US, report the first successful cultivation of the ubiquitous SAR11 marine bacterioplankton clade (Nature 2002, 418:630-633).

Rappe et al. inoculated fresh Oregon coast seawater samples into microtitre dish wells by dilution, such that each well received 22 microbial cells. The culture media consisted of sterile Oregon coast seawater supplemented with a combination of phosphate, ammonium and a defined mixture of organic carbon compounds. Under these conditions, they were able to grow eighteen cultures of representatives of the SAR11 clade. They successfully passaged eleven of these cultures and cryopreserved them for future study.

"Because of their extraordinarily small size, the study of these isolates should...