Sulfate-Reducing Bacteria Reveal a New Branch of Tetrapyrrole Metabolism

Sulfate-reducing microorganisms are a diverse group of bacteria and archaea that occupy important environmental niches and have potential for significant biotechnological impact. Desulfovibrio, the most studied genus among the sulfate-reducing microorganisms, contains proteins with a wide variety of tetrapyrrole-derived cofactors, including some unique derivatives such as uroporphyrin I and coproporphyrin III. Herein, we review tetrapyrrole metabolism in Desulfovibrio spp., including the production of sirohaem and cobalamin, and compare and contrast the biochemical properties of the enzymes involved in these biosynthetic pathways. Furthermore, we describe a novel pathway used by Desulfovibrio to synthesize haem b, which provides a previously unrecognized link between haem, sirohaem, and haem d ₁ . Finally, the organization and regulation of genes involved in the tetrapyrrole biosynthetic pathway is discussed.