Fig. 4: Endolysin-triggered disintegration of the cell wall induces L-form conversion.

a–c, Cryotomograms of L. monocytogenes Rev2 cells revealing the effects of endolysin Ply006 exposure on the bacterial cell wall in situ. a, Representative Rev2 walled cell with intact cytoplasmic membrane (CM) and peptidoglycan (PG) layer. Shown is a 26-nm-thick slice through a cryotomogram. b,c, Different stages of CM blebbing (white arrows) in response to Ply006 exposure for 1 min (top) and corresponding segmented 3D model (bottom). Shown are representative images of CM extrusions emerging from different cells. CM protrudes through lesions in the peptidoglycan layer, predominantly at the cellular poles. Blebbing occurs in different stages, ranging from small membrane protrusions (i) to blebs filled with cytoplasmic content (ii) and membrane-bound L-form-like vesicles (iii). Shown are 15-nm-thick tomographic slices (green, PG; blue, CM). c, L-form-like vesicle completely lacking detectable PG structures. A primary internal vesicle (PIV) located within the cell is clearly visible. A 22-nm-thick tomographic slice is shown. d–f, Cryotomograms of E. faecalis Rev cells revealing the cell wall architecture in situ before (d) and after treatment with endolysin Ply007 (e,f). d, Dividing E. faecalis coccus with a distinct PG layer and CM membrane. Shown is a 28-nm-thick tomographic slice. e,f, CM blebbing and induction of L-form-like vesicles in response to Ply007 exposure. Shown are 22-nm-thick tomographic slices. g, Cryotomogram of an A006 virion attaching to a Rev2 host cell, 5 min post infection (bottom). Shown is an 18-nm-thick tomographic slice. h, Cryotomogram of an Efs7 phage attachment to an E. faecalis Rev host cell, 10 min post infection. A 22-nm-thick tomographic slice is shown. The micrographs are representative of at least three independent experiments (a–h). Scale bars, 100 nm. Also see Supplementary Videos 8 and 9.