Caffeine-death in Escherichia coli

Autor: Grigg Gw
Rok vydání: 1968
Předmět:
Zdroj: Molecular and General Genetics MGG. 102:316-335
ISSN: 1432-1874
0026-8925
DOI: 10.1007/bf00433723
Popis: Growth of a culture of E. coli strain B or 15 in medium containing caffeine resulted in the accumulation of inviable cells in the population. A caffeine concentration of 8 mM caused the death of between 30% and 50% of the cells in 12 independent populations grown for 15 generations or more. The thymine dimer excision-defective strains Bs-1, Bs-8 and Bs-12 and the exr− mutant Bs-2 were resistant to this lethal effect. The reckless, hcr+ mutant Bs-11 was more sensitive than the parental B strain. Although 100mM caffeine did not impair DNA synthesis in vitro, concentrations of the drug ≤8 mM caused a significant decline in DNA synthesis in vivo in E. coli B cells. From the fit of an experimental growth curve to an algebraic model of growth in which a proportion of cells are inactivated at each replication it is suggested that caffeine does not affect the replication rate of the viable cells. The observed impairment of DNA synthesis in vivo is equated with this cell death (caffeine-death). For E. coli 15 or B, 8 mM caffeine induced caffeine-death at a rate of 18% per cell generation. Caffeine-resistant mutants of E. coli B and E. coli 15 were isolated. Of those studied in detail a substantial proportion proved to be U.V. and X-ray sensitive and excision-defective. Others were more U.V. and X-ray resistant than strain B. Yet another class proved highly unstable. A chromosome breakage model of caffeine-death implicating enzymes of the excision-repair process is discussed.
Databáze: OpenAIRE
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