Abstract
Endogenous photosensitization in a carotenoidless mutant of Rhodopseudomonas spheroides has been studied. When this mutant is exposed to visible light and oxygen there is a short lag period followed by exponential killing of the cells. The killing process obeys the Bunsen-Roscoe law of reciprocity and is temperature-independent. The chlorophyll content of the cells does not affect the rate of killing until a certain low threshold has been reached. Exposure of photosynthetically grown cells to air in the dark induces a temporary desensitization to the killing. A certain proportion of the population is invariably resistant to the photokilling. Evidence is presented to show that the resistance of these cells is probably a result of their abnormally low chlorophyll content. One consequence of the irradiation is the appearance of abnormally small colonies upon plating the survivors. This is interpreted in terms of a multi-hit theory. The photosensitizing pigment itself (the intracellular bacteriochlorophyll) is destroyed. The process is zero order, temperature-dependent, and does not follow the reciprocity law. It is suggested that the death of the cell results from a disruption of the cell membrane.
Full Text
The Full Text of this article is available as a PDF (571.8 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- COHEN-BAZIRE G., SISTROM W. R., STANIER R. Y. Kinetic studies of pigment synthesis by non-sulfur purple bacteria. J Cell Physiol. 1957 Feb;49(1):25–68. doi: 10.1002/jcp.1030490104. [DOI] [PubMed] [Google Scholar]
- GRIFFITHS M., SISTROM W. R., COHENBAZIRE G., STANIER R. Y., CALVIN M. Function of carotenoids in photosynthesis. Nature. 1955 Dec 24;176(4495):1211–1215. doi: 10.1038/1761211a0. [DOI] [PubMed] [Google Scholar]
- GRIFFITHS M., STANIER R. Y. Some mutational changes in the photosynthetic pigment system of Rhodopseudomonas spheroides. J Gen Microbiol. 1956 Jul;14(3):698–715. doi: 10.1099/00221287-14-3-698. [DOI] [PubMed] [Google Scholar]
- KAPLAN R. W. Dose-effect curves of s-mutation and killing in Serratia marcescens. Arch Mikrobiol. 1956;24(1):60–79. doi: 10.1007/BF00418422. [DOI] [PubMed] [Google Scholar]
- NEWTON J. W., NEWTON G. A. Composition of the photoactive subcellular particles from Chromatium. Arch Biochem Biophys. 1957 Sep;71(1):250–265. doi: 10.1016/0003-9861(57)90026-7. [DOI] [PubMed] [Google Scholar]
- SISTROM W. R., GRIFFITHS M., STANIER R. Y. The biology of photosynthetic bacterium which lacks colored carotenoids. J Cell Physiol. 1956 Dec;48(3):473–515. doi: 10.1002/jcp.1030480309. [DOI] [PubMed] [Google Scholar]