1. Under a variety of conditions in which cells are infected with one or a few virus particles and the host cells are killed, but no infective particles or virus material is formed as indicated by plaque count, one-step growth curve, or protein or desoxyribonucleic determinations, the cells neither lyse nor release ribonucleic acid into the medium. 2. The "killing" effect of S. muscae phage is separate from its lytic property. 3. The release of ribonucleic acid into the medium is not simply due to the killing of the cell by the virus, and ribonucleic acid is never found in the medium unless virus material is synthesized. 4. Infected cells of S. muscae synthesizing virus release ribonucleic acid into the medium before cellular lysis begins and before any virus is liberated. 5. The higher the phage yield the more ribonucleic acid is released into the medium before any virus is released. 6. Phage may be released from one strain of Staphylococcus muscae without cellular lysis, although bacterial lysis begins shortly after the virus is released. In another strain, infected under similar conditions, virus liberation occurs simultaneously with cellular lysis. 7. The viruses liberated from both bacterial strains appear to be the same in so far as they cannot be distinguished by serological tests, have the same plaque type and plaque size, and need the same amino acids added to the medium in order to grow. Furthermore, the virus liberated from one strain can infect and multiply in the other strain and vice versa. 8. It is suggested that virus synthesis, in S. muscae cells infected with one or a few phage particles, leads to a disturbance of the normal cellular metabolism, resulting in lysis of the host cell.

Bacteriophages↗

PubMed1952

Phage formation in Staphylococcus muscae cultures. XI. The synthesis of ribonucleic acid, desoxyribonucleic acid, and protein in uninfected bacteria.

1. The synthesis of ribonucleic acid, desoxyribomicleic acid, and protein in S. muscae has been studied: (a) during the lag phase, (b) during the early log phase, and (c) while the cells are forming an adaptive enzyme for lactose utilization. 2. During the lag phase there may be a 60 per cent increase in ribonucleic acid and protein and a 50 per cent increase in dry weight without a change in cell count, as determined microscopically, or an increase in turbidity. 3. During this period, the increase in protein closely parallels the increase in ribonucleic acid, in contrast to desoxyribonucleic acid, which begins to be synthesized about 45 minutes after the protein and ribonucleic acid have begun to increase. 4. The RNA N/protein N ratio is proportional to the growth rate of all S. muscae strains studied. 5. While the RNA content per cell during the early log phase depends upon the growth rate, the DNA content per cell is fairly constant irrespective of the growth rate of the cell. 6. Resting cells of S. muscae have approximately the same RNA content per cell irrespective of their prospective growth rate. 7. While the cells are adapting to lactose, during which time there is little or no cellular division, there is never an increase of protein without a simultaneous increase in ribonucleic acid, the RNA N/protein N ratio during these intervals being approximately 0.15. 8. Lactose-adapting cells show a loss of ribonucleic acid. The purines-pyrimidines of the ribonucleic acid can be recovered in the cold 5 per cent trichloroacetic acid fraction, but the ribose component is completely lost from the system. 9. The significance of these results is discussed in relation to the importance of ribonucleic acid for protein synthesis.

Bacteriophages↗

PubMed1952

Bacterial viruses.

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Bacteriophages↗

PubMed1950

Phage formation in Staphylococcus muscae cultures. VII. Partial purification of the protein factor necessary for virus synthesis.

1. A substance is present in autolyzed pepsin solutions which stimulates the release of phage by some strains of S. muscae when added to Fildes' synthetic medium. 2. The substance is assayed by determining the quantity necessary to increase the phage yield to one-half the maximum value, using the one-step growth curve technique. 3. The substance has been concentrated and partially purified (500-fold) by heavy metal precipitation, butyl alcohol extraction, and absorption on norit. 4. No known amino acid or accessory growth substance tested could replace this substance.

Bacteriophages↗

PubMed1950

Phage formation in Staphylococcus muscae cultures. VIII. Effect of the protein factor and aspartic acid on virus synthesis with various bacterial strains.

1. Four strains of Staphylococcus muscae have been isolated which differ in their growth rates and phage syntheses in Fildes' synthetic medium. 2. Two of the strains when singly infected cannot release phage in Fildes' synthetic medium unless a substance present in certain acid-hydrolyzed proteins is added to the medium. One of these strains also requires other substance(s) present in acid-hydrolyzed proteins in order to grow in Fildes' medium. 3. The two strains which do not require the addition of the phage-stimulating factor have been found either to synthesize this substance, or one similar to it. One of these strains will not grow in Fildes' medium unless substance(s) present in acid-hydrolyzed proteins is added to the medium. 4. The purified acid-hydrolyzed protein factor necessary for virus liberation does not affect the multiplication rate of uninfected S. muscae cells in Fildes' synthetic medium. 5. The substance is not needed for the adsorption or the invasion of the host cell by the virus. In the absence of the factor, the virus is adsorbed to the cell and "kills" it. 6. An analysis carried out by means of the one-step growth curve technique has indicated that the substance is not concerned simply with the mechanism of virus release, but is necessary for some initial stage in virus synthesis. 7. With one bacterial strain not requiring the AHPF, aspartic acid had to be present at least during the minimum latent period for the cell to form virus. 8. In the absence of aspartic acid, the virus was adsorbed to the cell and killed it, but no virus was released from singly infected bacteria. 9. If the cells were grown in a medium containing aspartic acid and then resuspended in the medium minus aspartic acid, no virus was released, although such cells contained at least two times the amount of aspartic acid necessary for the burst size in the complete medium. 10. Aspartic acid, a constituent of the virus particle, appears from an analysis of one-step growth curves to take part in the initial phase of phage synthesis. 11. The effect of amino acids on virus formation is discussed in relation to the time sequence of virus protein and desoxyribonucleic acid synthesis.

Aspartic Acid↗

PubMed1950

Phage formation in Staphylococcus muscae cultures. IX. Effect of multiple infection on virus synthesis in the absence and presence of specific substrates.

1. A strain of S. muscae which requires a substance present in certain acid-hydrolyzed proteins (AHPF) for virus liberation when singly infected in Fildes' synthetic medium no longer needs this substance when multiply infected. 2. In the absence of the AHPF under conditions of multiple infection the amount of phage released is approximately equal to the number of infecting particles between two to ten. Over ten particles per cell has no further effect on the yield of virus. 3. The experimental evidence indicates that it is the phage particle and not some other component in the lysate which can replace the AHPF. 4. The minimum latent period and rise period of cells singly infected in the presence of the AHPF and multiply infected in the absence of the AHPF are the same. 5. The desoxynucleic acid synthesis of cells, infected with a very few virus particles in the presence of excess AHPF and multiply infected with ten particles in the absence of the AHPF, occurs at approximately the same rate, with both infected samples synthesizing about the same amount of desoxynucleic acid and liberating the same yields of virus. 6. A strain of S. muscae which requires aspartic acid for virus synthesis when singly infected does not need this substance when multiply infected, the burst size under the latter conditions depending upon the multiplicity of infection between 3 to 12 particles per cell. 7. The data indicate that the virus released from multiply infected cells in the absence of added AHPF or aspartic acid is newly synthesized virus and not the original infecting particles. 8. The phage particle contains the AHPF and aspartic acid. 9. As a tentative working hypothesis, it is assumed that the AHPF and aspartic acid for phage formation under conditions of multiple infection, in the absence of added AHPF, or of aspartic acid, are contributed by the original infecting particles. 10. Ultraviolet-inactivated phage is adsorbed to the host cell and kills the cell although little virus is released under the experimental conditions. 11. Ultraviolet-inactivated phage particles, if added before the active particle is adsorbed, will greatly inhibit the liberation of new virus particles; but does not do so if added a few minutes after the active particle has been adsorbed. 12. Under the experimental conditions, reactivation of phage when present in multiply infected cells does not occur; and such ultraviolet-inactivated phage cannot serve as a source of the AHPF or aspartic acid, although the AHPF can be liberated from such inactivated particles by acid hydrolysis. 13. The results are discussed in relation to Luria's experiments with ultraviolet-treated phage and to his "gene pool" hypothesis of phage formation.

Aspartic Acid↗