DETERMINATION OF BASE RATIOS OF SIX RIBONUCLEIC ACID BACTERIOPHAGES SPECIFIC TO ESCHERICHIA COLI

1. A method is described for the isolation of single-stranded-RNA coliphages. Two of the six RNA coliphages investigated were new strains. 2. The base ratios of six RNA coliphages were determined by labelling the host bacterium with [(32)P]-phosphate, purification of the radioactive coliphages and separation of 2',3'-ribonucleotides liberated by alkaline hydrolysis of the coliphage RNA. 3. All six of the coliphages were morphologically similar, contained single-stranded RNA, and had sedimentation coefficient 80+/-5s. 4. The six RNA coliphages fell into two distinct groups, both serologically and in terms of their RNA base ratios.

BOUND WATER, INOSITOL, AND THE BIOSYNTHESIS OF TEMPERATE AND VIRULENT BACTERIOPHAGES BY AIR-DRIED ESCHERICHIA COLI

The effect of relative humidity (R.H.) and inositol on the capacity of semidried cells of E. coli B to manufacture five bacteriophages, together with the effect of drying on the vegetative phages of infected cells, has been studied. Also, the action of drying and inositol on the induction of lysis and production of lambda phage by E. coli K12 has been examined. It was found that the bound-water content of a cell determined the response of all phenomena to drying. As the R.H. was lowered from 70%, where the bound-water content is approximately 25 g/100 g cell solids, to 40% (10 g/100 g cell solids) a rapid decline in the resistance of both the capacity and vegetative phage occurred. In addition, the extent of vegetative phage inactivation was found to depend on the time after infection and prior to drying. All vegetative phages showed their maximum sensitivity immediately and up to 7 minutes after infection, then their sensitivity decreased and maximal stability occurred 15 minutes after infection. Inositol completely prevented capacity or vegetative phage inactivation under the conditions described. Desiccation was found to induce the lysis of E. coli K12 and the production of lambda phage. In terms of the percentage of viable cells lysed a greater proportion of the cells surviving desiccation at 30% R.H. was found to undergo lysis than those desiccated at 70% R.H., or at all R.H. levels in the presence of inositol.

QUANTITATIVE STUDY OF ENDOLYSIN SYNTHESIS DURING REPRODUCTION OF LAMBDA PHAGES

Groman, Neal B. (University of Washington, Seattle) and Grace Suzuki. Quantitative study of endolysin synthesis during reproduction of lambda phages. J. Bacteriol. 86:187-194. 1963.-Endolysin is presumed to be a phage-induced enzyme participating in lysis through its destructive action on the host cell wall. A method for assaying endolysin is described, which was utilized in studying endolysin synthesis at 37 and 44 C by induced strains of K-12 (lambda), K-12 (lambdatem), and K-12 (lambda112). In all cases, endolysin was detected prior to the appearance of mature, intracellular phage and was detected earlier at 44 C than at 37 C. It was synthesized at a linear rate, as was phage, and both syntheses terminated at the same time. Surprisingly, endolysin also accumulated under conditions in which induced K-12 (lambda112) exhibited lysis inhibition. Under these conditions, endolysin concentration per induced cell was 2 to 2.5 times that produced by normally lysing K-12 (lambda). Since alterations introduced into the lytic process by temperature, mutation, or both correlate well with the timing and rate of endolysin synthesis, the data tend to support the concept that endolysin determines the kinetics of the process. However, the accumulation of endolysin during lysis inhibition suggests the need for alternative hypotheses. One hypothesis is that although endolysin action is the key to lysis some preliminary steps are required to release the enzyme so that it may contact its substrate in the cell wall. A second hypothesis is that basically the lytic process involves an alteration in the permeability barrier of the cell and that lytic enzymes such as endolysin have evolved as an auxillary but dispensable mechanism to this process.

SYSTEM FOR DETECTING INDUCERS OF LYSOGENIC ESCHERICHIA COLI W1709 (LAMBDA) AND ITS APPLICABILITY AS A SCREEN FOR ANTINEOPLASTIC ANTIBIOTICS

Studies were conducted to determine conditions of maximal sensitivity for a test system designed to detect chemical inducers of phage production in the streptomycin-dependent, lysogenic Escherichia coli strain W1709(lambda). This strain was found to be induced by all antibiotics previously reported to be inducers of E. coli K-12(lambda). However, the system employing W1709(lambda) proved superior for screening fermentation filtrates because its growth, in contrast to that of K-12(lambda), was not stimulated during the induction period by filtrate nutrients. Thus, misleading high phage counts, which accompany cell growth stimulation, were not produced by filtrates devoid of inducing activity. The inducing capability of 95 fermentation filtrates, each containing an unidentified antibiotic(s) inhibitory for one or more transplanted rodent tumors, was determined in the W1709(lambda) system. A low incidence of inducers was found among inhibitors of sarcoma 180, adenocarcinoma 755, solid myeloid leukemia C1498, and adenocarcinoma of the duodenum in the hamster. However, seven of eight filtrates active against leukemia 1210 had induction capability. From a screen of actinomycete culture filtrates, 28 of the first 1,000 were identified as producers of induction activity. Thus far, of the nine cultures from this group that were subjected to examination, eight demonstrated at least presumptive evidence of antineoplastic activity.