. Classic papers in genetics. Genetics; Genetics. ZINDER AND LEDERBERG 225. CELL COUNT Fig. 1. Assay of FA. FA (LT-2) and cells (LA-22) were mixed at various dilutions and plated on minimal agar. Prototrophs were counted after 48 hours. tivate FA was of particular interest. Enzymatic activity was verified by testing samples of the reaction mixture for reduction of the viscosity of thy- mus nucleic acid (kindly supplied by Dr. R. D. Hotchkiss). Similar controls were not done for the other enzymes. Evocation of FA. The properties of phages latent in Salmojiella have been summarized by Burnet and
. Classic papers in genetics. Genetics; Genetics. ZINDER AND LEDERBERG 225. CELL COUNT Fig. 1. Assay of FA. FA (LT-2) and cells (LA-22) were mixed at various dilutions and plated on minimal agar. Prototrophs were counted after 48 hours. tivate FA was of particular interest. Enzymatic activity was verified by testing samples of the reaction mixture for reduction of the viscosity of thy- mus nucleic acid (kindly supplied by Dr. R. D. Hotchkiss). Similar controls were not done for the other enzymes. Evocation of FA. The properties of phages latent in Salmojiella have been summarized by Burnet and McKie (1929) and Boyd (1951). Lysogenic phages, , those obtained from lyso- genic bacteria, poorly lyse sensitive cultures and readily provoke second- ary resistant lysogenic forms. Visible lysis of sensitive cells is observed only at low multiplicities of infection. With higher multiplicities there is little evi- dence of lysis. When phage is added to broth cultures, the tube does not clear, and the bacteria grow at a re- duced but significant rate. PLT-22 is typical of these phages. To determine whether PLT-22 was unique in its FA evoking activity, a variety of treatments was applied to resting and growing cells of LT-2 strains. FA was not detected in the filtrates of young cultures or after autolysis with benzene, extraction of dried cells, treatment with high con- centrations of antibiotics (penicillin, bacitracin, and aureomycin), or com- plete phage lysis. Dilute antibiotics, lithium chloride, and crystal violet yielded variable FA. High activity is most readily detected in the filtrates of cultures treated with lysogenic phages. These results indicate that FA is not released by mechanical, chemical, or biological disruption of cells. How- ever, various deleterious agents elicit its appearance in a way that may parallel the action of latent phage. The most effective concentrations of these reagents were those which only slightly inhibited the cells. FA has also been
Size: 1718px × 1454px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectgenetics
