The members of this family are periplasmic cytochromes that have been shown to be directly involved in metabolic pathways that lead to removal of Fe(III), U(VI) and Cr(VI). This family is composed by five triheme cytochromes in both G. sulfurreducens and G. metalllireducens and their study aims to understand the structure-function mechanisms within each individual member but also how they interact with physiological partners in the electron transfer chain of Gs.