Fig. 2
Resistance of B. intestinalis APC919/174 to ΦcrAss001 is reversible and associated with capsular polysaccharide alterations and loss of phage adsorption. a Spotting of 4x107 pfu of ΦcrAss001 on B. intestinalis APC919/174 agar overlay results in turbid clearing zone; b–f TEM (x9900–105,000) of ultra-thin sections (80 nm) of samples taken from the center of the spot shows the presence of un-infected cells among lysed cell debris, infected cells with empty virions (“ghosts”) still attached, and cells in the process of division with phage progeny visible inside of them; g, h soft agar overlays inoculated with the same number of B. intestinalis CFU in the absence and presence of the excess of phage, respectively; i phenotypic dissociation of colonies of phage-resistant clone 8, (8W, “white” – phage-sensitive subclone; 8T, “transparent” – phage-resistant subclone); j kinetics of ΦcrAss001 adsorption to B. intestinalis phage resistant and sensitive clones; vertical axis, concentration of phage in the supernatant; horizontal axis, time passed after addition of phage; R, resistant clones (n=5); Rev, revertant sensitive sub-clones derived from one of the resistant clones; values are mean±SD from three independent experiments; k, l ultrathin section TEM visualization (x60,000) of altered cell surface morphology in phage-resistant clone 8T, compared to phage-sensitive WT strain; notable is the production of either loose or compact capsule; cm, cytoplasmic membrane; om, outer membrane