Nature Microbiology 2, 17017 (2017); published online 17 February 2017; corrected 6 March 2017.

In the version of this Letter originally published, the in-text citations to Supplementary Table 1 and Supplementary Data 1–7 were ambiguous. This has now been corrected in all versions of the Letter so that there is a clear distinction between the different files, with citations to Supplementary Table 1 and Supplementary Data 1–7 now appearing in the text. In addition, the definition of DIC in Fig. 2 was placed incorrectly. This has now been moved to Fig. 2b, in keeping with the figure panels.