Iron is the most abundant redox-active element in the solar system and the second most abundant redox-active element in Earth’s crust. The capacity for iron oxidation is broadly distributed among prokaryotes, and the activities of iron-oxidizing bacteria exert critical influence on many major elemental cycles, including the carbon cycle. Despite its importance, the fundamental biology of iron oxidation remains the poorest understood of any of the major metabolic pathways in the microbial world. Marinobacter aquaeolei, a facultative mixotrophic iron oxidizer, is an ideal model for the study of microbial iron oxidation because, in contrast to all other previously recognized neutrophilic iron oxidizers, it grows rapidly on plates and in liquid culture and is amenable to biochemical methods and genetic manipulation. Additionally, Marinobacter is one of the most ubiquitous classes of marine bacteria. It occurs throughout the water column and in the deep ocean. These microbes are members of hydrocarbon-degrading consortia and are capable of a variety of “extremophilic” lifestyles (psychrophily, oligotrophy, halotolerance). They also produce an unusual class of amphiphilic siderophores (iron transporter molecules with both hydrophilic and hydrophobic parts) that are thought to represent a unique mechanism for iron acquisition in marine bacteria. Low iron in the oceans limits primary productivity and carbon sequestration. The discovery that Marinobacter is also an iron oxidizer gives unprecedented opportunity to make rapid strides toward understanding “all things iron”–both biological iron oxidation and iron acquisition in the ocean. Sequencing M. aquaeolei benefits a broad community of microbiologists, oceanographers, and biogeochemists.
CSP project participants: Katrina Edwards (proposer), Mitchell Sogin (proposer), and Ashita Dhillon (Woods Hole Oceanographic Inst./ Marine Biological Laboratory).
Genome Portal Site: Marinobacter aquaeolei VT8