Nature 535, 435–439 (2016); doi:10.1038/nature18927

In this Letter, there were many errors in the reference citations. The original ref. 6 (Parks et al., 2015) should have been cited as ref. 32 in the Methods. There were also several other errors affecting both the reference list order and the citations throughout the main text and Methods. The references have been corrected in the online version of the Letter. We thank L. M. Rodriguez-R for bringing this to our attention.