This paper reports the results of an investigation of the effect of Zn2+, Mg2+, Cu2+, Ni2+, Fe2+, Fe3+, Mn2+ and Cr3+ ions present in the media on the kinetics of dissimilatory reduction of sulfates in Desulfotomaculum ruminis bacteria. It has been shown that the range of the optimum concentration of studied elements is different; sometimes very wide but sometimes very narrow. After a certain threshold concentration of a given element has been reached, its presence either causes total inhibition of the process or has a toxic effect.