Electron microscopic studies on the interaction between Lactobacillus phage PL-1 and cell walls isolated from its host cells.

Abstract

The envelope system as seen in the thin section of the cell of L. casei ATCC 27092 was of the multi-layered type. The transverse section of the isolated cell walls had an homogeneous appearance with a width of .apprx. 20 nm. The cell wall preparations were considered to correspond to the surface layer in the thin section of whole cells. EM examination of the mixtures of PL-1 phages and cell walls after fixation with osmic acid revealed that all the phages were adsorbed to cell walls in a tail-first orientation and that the adsorbed phages were intact. When the adsorption mixtures were not fixed with osmic acid, the adsorbed phages were eluted as infective virions by centrifuging and resuspending in fresh medium. In a control where the phages were mixed with the cell walls isolated from a phage-resistant strain named K-12, the phages showed no tendency to bind to the cell walls. Thin section of osmic acid-treated mixtures of phages and cell walls confirmed that the phages were bound by their tail tip to 1 side of cell wall preparations.