Convergent and divergent evolution of metabolism in sulfur-oxidizing symbionts and the role of horizontal gene transfer

► GammaSOX symbionts converge in their basic metabolism, oxidation of sulfur and CO2 fixation. ► GammaSOX symbionts differ greatly in additional metabolic capabilities involved in energy and carbon gain. ► Horizontal gene transfer may play a major role in the metabolic evolution of these symbionts. ► Phylogenies of metabolic genes provide insights into the ecology of symbionts. ► GammaSOX symbionts are excellent models for studying horizontal gene transfer.