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Abstract
SUMMARY: The killing of a population of a sensitive strain of Halobacterium halobium by halocin H4 followed exponential kinetics, and the percentage survival of sensitive cells exposed to different concentrations of halocin H4 corresponded to single-hit-type kinetics. Morphological changes were observed in treated cells, which showed swollen, spherical shapes. Halocin H4 affected macromolecule synthesis very little, and only late after the start of the treatment, although the transport of 2-aminoisobutyric acid, a non-metabolizable amino acid, was rapidly stopped. Bacteriorhodopsin-mediated H+ extrusion worked very efficiently in treated cells, and much larger pH decreases were found in treated than in untreated suspensions after illumination, although ATP synthesis was not markedly affected. These findings suggest that the primary target of halocin H4 may be located in the membrane, producing permeability changes and ionic imbalance, which lead to death and cell lysis.
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