Degradation of ribosomes and ribonucleic acid with bacteria starved for thymine and amino acids

Loudney, C.O.; White, Billie F.; Ferguson, Martha J.

doi:10.1016/0303-2647(67)90028-7

Cited by 1 publication

(4 citation statements)

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“…For example, in the complete absence of uracil (and consequently cytosine), DNA was still replicated, as measured by both '6Nand 3H-thymine incorporation, after TLD, but was not labeled after NA inactivation (unpublished data). This may suggest that there is less breakdown of ribosomes during NA treatment than TLD (16).…”

Section: Resultsmentioning

confidence: 97%

“…The differences observed in the labeling in the absence of either purines or pyrimidines may be related to the influence on nucleotide pools, or it may indicate that incorporation is influenced by turnover of ribosomal RNA. Doudney et al (16) showed that there is a great deal of ribosomal degradation during TLD in the presence and in the absence of required amino acids. Nevertheless, the results clearly show the extent of labeling bears little relation to the degree of immunity.…”

Section: Resultsmentioning

confidence: 99%

“…Some of the conditions which led to immunity were also those which allowed completion of a round of DNA replication. However, a major difficulty was the interpretation of conditions, since it was not possible to affect a single macromolecular event without affecting others (2,16,26,33). Deprivation of uracil led to apparent scavenging, presumably because of ribosomal breakdown (16).…”

Section: Discussionmentioning

confidence: 99%

“…However, a major difficulty was the interpretation of conditions, since it was not possible to affect a single macromolecular event without affecting others (2,16,26,33). Deprivation of uracil led to apparent scavenging, presumably because of ribosomal breakdown (16). Withdrawal of amino acids, or addition of CAP, could have had an effect on RNA (26,34).…”

Section: Discussionmentioning

confidence: 99%

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Thymineless Death in Escherichia coli : Deoxyribonucleic Acid Replication and the Immune State

Cummings

Kusy

1970

J Bacteriol

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Thymineless death (TLD) and nalidixic acid (NA) inactivation were studied in multiple auxotrophic strains of Escherichia coli B and B/r. As expected, it was found that both E. coli B and B/r exhibited an "immune state," i.e., a fraction of the population survived inactivation to both TLD and NA. With glucose as a carbon source in minimal medium, 0.1 to 0.3% of strain B and 0.2 to 0.5% of strain B/r survived inactivation; with acetate as the carbon source, the surviving fractions were increased to 1 to 2% and 5 to 7%, respectively. These immune fractions could be increased in magnitude by preincubation in minimal media containing thymine. Systematic analysis of the particular supplements necessary for the immune state indicated that the absence of the required amino acids was essential for the maximal expression of immunity. However, immunity was not abolished in acetate medium even in the presence of the required supplements. Further studies on the replication of deoxyribonucleic acid (DNA) during preincubation indicated that the degree of immunity did not necessarily correlate with the completion of a round of DNA replication. This finding was supported by examining the immune state in synchronous populations. In both glucose and acetate medium, there was no significant change in the degree of immunity to inactivation within the cell cycles of E. coli B and B/r. We concluded that some other event, possibly inhibition of protein synthesis, was necessary in determining the degree of the immune state. DNA replication was investigated after TLD and NA inactivation, and, as expected, it was found that both events led to premature initiation of replication. The only differences observed in the effects of these two processes on DNA synthesis were the following. (i) NA-induced replication was less sensitive to chloramphenicol than was TLD. (ii) TLD-induced replication was unaffected by pretreatment of the cells with mitomycin C, but this pretreatment prevented the replication of DNA after NA treatment. It was suggested that the mechanism of action of NA could involve a monofunctional attack on the DNA.The mechanism by which thymine-requiring microorganisms lose viability when deprived of thymine is still unknown (8,11,18,27,39). Many attempts have been made to elucidate such a mechanism, but, to date, few positive results have been obtained. Hanawalt (18) suggested that the synthesis of some messenger ribonucleic acid (RNA) was involved in the thymineless death (TLD) observed in Escherichia coli (15). However, it has been shown (39) that the rapidly labeled RNA synthesized during TLD in E. coli K-12 has the same base composition as total RNA, indicating that no gross changes occur in the RNA synthesized. In addition, Luzzati (27) found that E. coli 15 exponentially lost its ability to synthesize messenger RNA during thyniine starvation, because of the inability of the deoxyribonucleic acid (DNA) to serve as a template for RNA polymerase. Purification of the DNA after thymine starvation led to an increase in the primi...

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%