We thank G. Chen, J.-D. Sauer, E. Stevens, M. Marco and N. Freitag for providing bacterial strains; H. Carlson, A. Williamson and J. Coates for helpful feedback; and N. Garelis for experimental assistance. Research reported in this publication was supported by funding from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health (F32AI136389 to S.H.L., 1P01 AI063302 to D.A.P., and 1R01 AI27655 to D.A.P.), the Office of Naval Research (N0001417WX01603 to C.M.A.-F.), and the China Scholarship Council (no. 201606090098 to L.S.). A mass spectrometer used in this study was purchased with NIH support (grant 1S10OD020062-01). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231.

Reviewer information

Nature thanks N. Freitag, J. Gralnick, K. Nealson and G. Reguera for their contribution to the peer review of this work.