Influence of pH on proliferation of lactic streptococcus bacteriophage

Variations in the production of lactic acid by bacteria can be of major im-portance in the dairy industry, especially in the making of cheddar and cottage cheese. One of the principal causes for failure of organisms to produce acid is bacteriophage. This study was undertaken to determine the influence of the re-action of the medium on the proliferation of lactic streptococcus bacteriophage. Nelson et al. (1939) found that a reaction approximating pH 6.8 was most favorable for the lysis of sensitive strains of Streptococcus lactis. Turner (1948) found the reaction of the medium an important factor in plaque formation by the lactic streptococcus bacteriophage, pH 6.0 to 6.2 being optimum for most strains. Cherry and Watson (1949) suggested that pH 5.0 was about the critical level below which lysis could not occur for S. lactis 122-4. Gold and Watson (1950) found that the pH of the medium was the limiting factor in the lysis of the cells of Clostridium madisonii by the homologous bacteriophage. Krueger and Fong (1937), in their work with Staphylococcus aureus, found that increasing the hydrogen ion concentration prolonged the lag phase of the organism withou