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In this Letter, we omitted to cite ref. 1, which presents a cryo-electron-microscopic map of the Shigella flexneri needle at a resolution of 7 Å, significantly higher than for previous maps. Our Salmonella typhimurium needle model (2.1-Å backbone) fits very well into this high-resolution cryo-electron-microscopic map, and observed differences regarding the location of the amino terminus will be discussed in a future publication. In addition, we acknowledge Microsoft’s donation of Windows Azure computing resources and technical support to carry out the Rosetta calculations of the needle structure.