Publisher Summary Sulfur is an absolute requirement for growth of all organisms. Its most important role is in the amino acids, cysteine and methionine, in proteins, where cysteine residues, in particular, are important in determining enzyme structure, and the metal-binding properties of sulfur help catalyze a variety of enzyme reactions. Recent years have seen some modification of how to understand the details of this microbially mediated sulfur cycling, as technological advances now allow a more defined speciation of the soil sulfur based on molecular spectroscopic studies rather than chemical reactivity. First evidence is that two groups of bacteria (Comamonadaceae and Rhodococci) may play a specialized role in sulfonate cycling in the soil, with the Comamonadaceae being particularly active. Mycorrhizal fungi are also important in providing sulfur to plants, probably in association with bacteria, and protozoa may also play an important role. Our understanding of how soil organosulfur is converted to plant-available sulfur, and how this process is regulated, has made considerable advances in the last few years.