UNBLAANCED DEOXYRIBONUCLEIC ACID SYNTHESIS: ITS ROLE IN X-RAY-INDUCED BACTERIAL DEATH

Journal Article · Tue Aug 20 04:00:00 EDT 1963 · Biochimica et Biophysica Acta (Netherlands)

DOI:https://doi.org/10.1016/0006-3002(63)90287-7· OSTI ID:4623520

Billen, D

BS>A study was made of the effects of unbalanced DNA synthesis on subsequent cell physiology and x-ray sensitivity of the polyauxotroph, Escherichia coli strain 15T-A-U(thymine, arginine, and uracil dependent) with the following results: DNA replication, proceeding to completion in the absence of concomitant protein and RNA synthesis, resulted in a cell population with an enhanced DNA content and with increased resistance to the lethal effects of x-ray exposure. This resistance was expressed as an increase in the shoulder of the dose --survival curve and an increase in the mean lethal dose. Renewal of both protein and RNA synthesis after completion of unbalanced DNA synthesis reversed the resistant state. The presence of both arginine and uracil were required for maximum reversal. When only uracil was added, no change in sensitivity was seen. Addition of only arginine resulted in partial resensitization. Incubation of exponential cells in a medium lacking thymine as well as arginine and uracil led to thymine-less death as well as a sensitization to x rays. This was characterized by a shift from sigmoidal to exponential killing. Substitution of 5bromouracil for thymine during unbalanced DNA synthesis did not interfere with the completion of DNA synthesis. Buoyant density-gradient analysis in CsCl showed that only normal and hybrid DNA were present in such cells. Equilibrium centrifugation of DNA obtained from cells incubated with bromoSTAC/sup 14!-uracil provided confirmation that only hybrid DNA was made during the unbalanced DNA synthesis period. Such cells did not exhibit enhanced resistance to x rays, but to the contrary were more sensitive than the control population. (auth)

• Research Organization: Univ. of Texas, Houston
• NSA Number: NSA-17-040572
• OSTI ID: 4623520
• Journal Information: Biochimica et Biophysica Acta (Netherlands), Journal Name: Biochimica et Biophysica Acta (Netherlands) Vol. Vol: 72; ISSN BBACA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

AMINO ACIDS
ARGININE
BACTERIA
BIOCHEMISTRY
BIOLOGY AND MEDICINE
BROMINATED HYDROCARBONS
CARBON 14
CENTRIFUGATION
CESIUM CHLORIDES
DENSITY
DIAGRAMS
DNA
ESCHERICHIA COLI
HETEROCYCLICS
IRRADIATION
KETONES
LABELLED COMPOUNDS
LETHAL DOSE
METABOLISM
MICROORGANISMS
NUCLEIC ACIDS
ORGANIC BROMINE COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYSIOLOGY
PROTEINS
PYRIMIDINES
RADIATION DOSES
RADIATION EFFECTS
RADIOSENSITIVITY
RIBONUCLEIC ACID
SURVIVAL TIME
SUSPENSIONS
THYMINE
TRACER TECHNIQUES
URACILS
VARIATIONS
X RADIATION