Biochemical Effects of Technetium-99-Pertechnetate on Microorganisms

The biochemical effects of technetium-99 as pertechnetate (TcO(4) (-)) were investigated in a variety of microorganisms (a nonsulfur purple bacterium, five blue-green algae, a protozoan, a diatom, two heterotrophic bacteria, a red alga and two green algae). Sensitivity to pertechnetate as measured by growth ranged from marked inhibition at 1 mug Tc/ml (nonsulfur purple bacterium) to no effect at 600 mug Tc ml (both green algae). No correlation between organism type and growth susceptibility to pertechnetate was apparent. The blue-green alga, Agmenellum quadruplicatum strain PR-6, bound technetium-99 to a level of 3 mug/mg dry weight cells (from medium containing 1.5 mm pertechnetate) in the light, but little or none in the dark; cell death occurred only with uptake. Addition of TcO(4) (-) to the medium caused a rapid but temporary increase in ATP levels of PR-6 (in the light only) and Tetrahymena pyriformis strain WH14. Respiration of organisms WH14 and Bacillus subtilis and photosynthesis of organism PR-6 were immediately slowed by the introduction of pertechnetate. Technetium as pertechnetate has a possible biochemical effect on cells, unrelated to its radioactivity or to a general oxidation effect.