Correction to: Nature Microbiology https://dx.doi.org/10.1038/s41564-017-0030-5 (2017); published online 2 October 2017.
In the version of this Letter originally published, the authors incorrectly stated that primers 28F-519R were reported in ref. 54 to underestimate the abundance of SAR11 in the ocean. This statement has now been amended in all versions of the Letter.
The original article can be found online at https://doi.org/10.1038/s41564-017-0030-5.