Manganese was shown to be an essential trace metal for growth and thiosulphate oxidation by Thiobacillus versutus in chemostat culture. In the thiosulphate-oxidizing enzyme system of T. versutus, protein B was the only component found to contain manganese in significant amounts. When it was examined by electron spin resonance (ESR) spectroscopy, protein B gave a broad, complex spectrum, indicative of the presence of a dimeric manganese cluster, with manganese in the Mn(II) oxidation state.
