Symposium on the biology of cells modified by viruses or antigens. III. Physiological conditions for studies of viral biosynthesis in mammalian cells.

The present paper will consider some of the bacteriophage, (b) confers immunity to attack changes which become apparent in bacterial by that phage, and (c), in the inducible systems strains once they have been rendered lysogenic. we shall consider, it may also endow the cell The new attributes which lysogenized bacteria with an enhanced sensitivity to ultraviolet light. take on may be due to introduced bacteriophage Other properties are sometimes superposed (phage) genes, introduced bacterial genes, or a upon these effects. For example, a strain of combination of the two. For the moment let us Bacillus megaterium studied by Ionesco (1953) concern ourselves with the extent to which any normally forms smooth colonies; yet, once it is lysogenic cell differs from its nonlysogenic lysogenized with a certain megaterium phage, homologue. Every lysogenic cell carries a compleit and all its descendants grow as rough, wartment of phage genes in the form of prophage. like colonies. The presence of prophage in this The presence of prophage renders the cell imcase alters the way in which the chains of bacilli mune to attack by homologous phage. The pile up to form a colony. To date, there are on level at which this immunity operates is intrarecord several lysogenic conversions of bacteria. cellular, for most lysogenic cells, like their nonWe will now consider two such phage-associated lysogenic counterparts, adsorb homologous changes in some detail. The first occurs in cerphage, are penetrated by its deoxyribonucleic tain lysogenic salmonellae; the second, in lysoacid (DNA) but do not yield to the destructive genic diphtheria bacilli. pattern that such DNA normally imposes on a sensitive cell. Occasionally, in every lysogenic BANTERIOPHAGEONOLYAC SYNTHIESIS IN S LMONEL AE population a bacterium lyses and releases phage. When a population of the kind of lysogenic bac. For the discovery of phage-induced conversions teria we shall consider here is exposed to mild in salmonellae we are indebted to several Japadoses of any of various peroxides or of ultranese workers. Izeki and Sakai (1953) demonviolet light, every cell lyses with the production strated that lysates of salmonella strains of of phage. In such a situation the prophage has group E2, characterized by somatic antigens 3 been induced to assume the vegetative phenoand 15, were capable of changing the serotype type and multiplies as phage with the resultant of strains of group El (somatic antigens 3, 10) destruction of the host cell. The lysogenic to that of group E2 (somatic antigens 3, 15). state, then, (a) entails the ability to liberate From the work of Uetake (1959) and Uetake 1 This symposium was held at the 59th Annual et at. (1955) (see also Terada et al., 1956; Meeting of The Society of American BacterioloHarada, 1956; Nakagawa, 1957; Uchida et al., gists in St. Louis, Missouri, on May 11, 1959, 1956; Uchida, 1957; reported from the Japanese under the sponsorship of the Division of Medical in Uetake et at., 1955 and 1958; Uetake, 1959; Bacteriology, Immunology, and Virology, with as well as Baron et al., 1957), it is clear that Dr. R. Walter Schlesinger as convener. several strains of salmonellae undergo changes