In the version of the article initially published, several labels in Figs. 2 and 3 were incorrect. In Fig. 2f and g, the second, light-blue “ΔfimH” label should have read “ΔfmlH”. In Fig. 2h, “Δfmlh” should have read “ΔfmlH”. In Fig. 2j, the second, light-blue “ΔfimH” label should have read “ΔfmlH”. In Fig. 2k, the first “ΔfmlH” (fifth lane) should have read “ΔfimH”. In Fig. 3b and d, the “∆fimH” label under the fifth bar of each graph should have read “∆fmlH”. In Fig. 3c, the second “ΔfimH” label (fifth lane) should have read “ΔfmlH”. In Fig. 3e, the second “ΔfimH” label (fifth lane) should have read “ΔfmlH”. These corrections have now been made to the HTML and PDF versions of the article.