Fig. S6.

AlpB can functionally substitute for the holin from bacteriophage λ. Plasmid pS105 contains the λSRRzRz1 lysis cassette placed downstream from the pR′ promoter. The λS105 gene (except the portion that overlaps with the R gene) in the plasmids pS105 and pS105R⁻ was replaced with the alpB gene to create pAlpB and pAlpBR⁻. Cultures of MC4100 λΔ(SR) carrying the pS105-derived plasmids were grown at 30 °C to A₅₅₀ of 0.3, thermally induced for 15 min at 42 °C, and aerated at 37 °C thereafter. Lysis curves were obtained by measuring A₅₅₀ after thermal induction. Time in minutes is shown. Cells containing pS105 (dark blue line) undergo rapid lysis after thermal induction, and pAlpB-containing cells also show a drop in turbidity after thermal induction (red line). The drop in turbidity is endolysin dependent, as cells that contain the plasmids pS105R⁻ (purple line) and pAlpBR– (light blue line), that lack a functional R gene, do not show the same phenotype. Additionally, the lysis is holin dependent, as the cells containing the pSam7 plasmid (green line) that produces a truncated holin also does not undergo lysis.