Programmed Death of Escherichia coli after UV Radiation
It is known that unicellular organisms are able to perpetuate themselves indefinitely. Under unfavorable conditions, however, they can meet their biological end-point. This end-point, i.e. cell death, is usually thought to be the result of passive “wearing out” processes. Senescence and death of human fibroblasts in vitro 1‚2 and even biological aging of higher organisms are also ascribed to such processes. It is assumed that errors in protein and DNA synthesis passively accumulate to the point where, due to impaired cell functions, death ensues 3‚4. In marked contrast to this,our recent results 5‚6 indicate that death of Escherichia coli cells after UV radiation might be an active “self-destruct” program.
KeywordsUnirradiated Control Interrupted Line Human Diploid Cell Strain Postreplication Repair Alkaline Sucrose Gradient
Unable to display preview. Download preview PDF.
- 5.M. Petranovié, E. Salaj-âmic, D. Petranovié, and Z. Trgovicevié, Inactivation of prophage in uv-irradiated Escherichia coli: Dependence on recA gene activity, J. Bact. 140: 848 (1979).Google Scholar
- 6.I. Trgovicevié, M. Petranovié, E. Salaj-tmic, D. Petranovié, and H. Qerimi, The cascade of “SOS” events, in: Progress in Environmental Mutagenesis, M. Alacevié ed., Elsevier/North Holland, Amsterdam (1980).Google Scholar
- 7.W. Hayes, The Genetics of Bacteria and their Viruses, Blackwell, Oxford (1968).Google Scholar
- 8.R. Sussman and F. Jacob, Sur un système de répression thermosensible chez le bactériophage d’Escherichia coli, C.R.Acad. Sci. 254: 1517 (1962).Google Scholar
- 9.P.A. Swenson, Physiological responses of Escherichia coli to far-ultraviolet radiation, in: Photochemical and Photobiological Reviews, vol. 1, K.C. Smith ed., Plenum, New York (1976).Google Scholar
- 11.B.J. Bachmann, Pedigrees of some mutant strains of Escherichia coli K-12, Bacteriol. Rev. 36: 525 (1972).Google Scholar
- 13.K.C. Smith and M.E. O’Leary, The pitfalls of measuring DNA synthesis kinetics as exemplified in ultraviolet radiation studies, Biochim. Biophys. Acta 169: 430 (1968).Google Scholar
- 14.G. Trgovicevié and W.D. Rupp, Lambda bacteriophage gene products and x-ray sensitivity of Escherichia coli: Comparison of red-dependent and gam-dependent radioresistance, J. Bact. 123: 212 (1975).Google Scholar