In the version of this Review originally published, the author contributions of co-author Arthur Neuberger were incorrectly listed. The author contributions should have appeared as 'D.D., X.W.-K., A.N., H.W.v.V., K.M.P., L.J.V.P. and B.F.L. researched data for the article, made substantial contributions to discussions of the content, wrote the article, and reviewed and edited the manuscript before submission'. This has now been corrected in all versions of the Review. The authors apologize to readers for this error.
Nature reviews. Microbiology
Department of Biochemistry, University of Cambridge, Cambridge, UK.