Action of hydroxyurea on Anabaena variabilis

Abstract

Low concentrations of hydroxyurea stimulated the growth of the blue-green alga Anabaena variabilis that had been pretreated with sublethal concentrations of chloramphenicol or of certain nucleic acid base analogues. When supplemented to the culture medium, hydroxyurea also counteracted the growth inhibitory effect of chloramphenicol on this organism. In contrast, when A. variabilis cells grown in the presence of hydroxyurea were subsequently treated with chloramphenicol, they were found to have become highly susceptible to the growth inhibitory effects of chloramphenicol. The growth of hydroxyurea pretreated cells in basal medium was attended by a lag that was shorter than that of untreated controls; on the other hand, when hydroxyurea pretreated cells were inoculated into chloramphenicol-supplemented medium, they exhibited a longer lag than that shown by untreated cells in chloramphenicol. The results obtained are discussed in terms of the probable effects of hydroxyurea and chloramphenicol on certain enzyme systems.