The sulfur cycle involves microbes, plants, and animals transforming sulfur into essential compounds. Microbes play a key role in breaking down sulfur compounds through different metabolic processes. Some microbes use sulfur as an energy source, while others use it in photosynthesis. These sulfur-transforming microbes form natural cycles in the environment. This microbial sulfur transformation has been happening for a long time and can be traced through isotopic effects in the geological record.