Chromium (Cr) is widely used in different industries, such as steel production, wood preservation, and leather tanning. It poses a severe threat to the ecological system due to its toxic effect on most life forms. In this paper, the response of Saccharomyces cerevisiae to different chromium concentrations was investigated. The results demonstrated that the growth of S. cerevisiae in the presence of chromium showed a lag phase much longer than in the absence of chromium. Inhibition was dependent upon the chromium concentrations. Chromium, at concentration of 15 muM, inhibited microbial growth by approximately 30% with regard to control, whereas chromium, at a concentration of 5 muM, did not have a significant effect on microbial growth. The existence of chromium did not perturb cell-protein synthesis and there was a good correlation between dry cell weights and total protein content (R = 0.98). The RNA/DNA ratio in the microbial cells varied with the chromium concentration and there was a significant positive correlation between chromium concentration and the RNA/DNA ratio. Assimilation of ammonium ion was inhibited by chromium in the medium. (C) 2003 Elsevier Ltd. All rights reserved.