Relation of endolysin to lysis by lambda bacteriophages.

the chambers. (ii) A drop of the culture is placed on the grid and then withdrawn until the fluid level is just below the surface of the grid; if the surface is wet, the covering film will not stick properly. (iii) The floor of the chamber is formed by dipping the cover slip through a film which has been previously cast on glass and stripped off onto a water surface; casting, stripping, and dipping of Formvar films were described in detail by Oster and Pollister (Physical Techniques in Biological Research, Academic Press, Ine., New York, 1956, vol. 3, p. 181). (iv) The cover slip is inverted over the well and the edges sealed with wax except at the side channels. After some experience, almost all such preparations should provide many usable microchambers. A small bubble is permissible, but the chamber should be completely closed off by the films. The only optical problem not common to other thick or wet-slide preparations is the deterioration of the image near the edge of the chamber due to diffraction effects and the curvature of the films. This can be seen in Fig. IA, which shows the smallest microchamber of the Ti grid; the central area of this chamber is satisfactory (Fig. iB), but chambers much smaller are not recommended. We have found such preparations valuable in our study of the limited division occurring in the presence of "bacteriostatic" concentrations of chloramphenicol and in the recovery of the culture after removal of the drug.