Fig. 4

MtLysX2 expression increases resistance to lethal acidic pH and delays biofilm formation. A Killing assay of M. smegmatis mc²155::MtlysX2 (MS322, dark gray) and mc²155::pROL_Hyg (MS321, light gray) at pH 4.5. Strains were grown for 24 h in Sauton medium at pH 5.5 before being transferred into the same medium at pH 4.5. *p = 0.48; **p = 0.01, ***p = 0.0045. B Biofilm formation in Sauton medium pH 5.5. Bacteria, grown to stationary phase were diluted 1:100 in Sauton medium pH 5.5. 4 ml of the suspension were than inoculated in a 24-well plate and incubated at 37 °C. Pictures were taken after 5, 6, 7, and 8 days (D). The experiment was repeated twice in triplicate obtaining comparable results