Thiols contain this element.
It's not chlorine, but the chlorobi phylum of bacteria is named for this element. A motif containing four atoms of this non-metal are found in aconitase. Vitamin B1 is named for the fact that it contains nitrogen and this element. In bacteria, nitrogen fixation occurs in a catalyst containing molybdenum and a cluster of iron and this element. This element, found in high concentrations in keratin, forms a tertiary structure called its namesake bridge. This element is found between ethyl and methyl groups in the side chain of methionine, and it's also found in cysteine.Thiols contain this element. For 10 points, name this element with symbol S.
It's not chlorine, but the chlorobi phylum of bacteria is named for this element.
sulfur [or S before mention]