Fe(II)-oxidizing microorganisms (FeOM) gain energy by Fe(II) oxidation, in the process fixing carbon, cycling nitrogen, and forming highly reactive Fe(III) oxyhydroxides that strongly bind phosphate, metals, and organic carbon. Despite their potential impact on a wide range of geochemical cycles, very little is known about the genetic mechanisms of FeOM, including energy conservation and nutrient cycling. To address this, we have been studying the (meta)genomics, transcriptomics, and biochemistry of Zetaproteobacteria, a class of marine FeOM. The Zetaproteobacteria often dominate high Fe(II) marine environments such as hydrothermal vents, but are also found in coastal sediments and stratified estuary environments. We will discuss findings from metagenome and transcriptome sequencing of Fe microbial mats from the Loihi Seamount, where Zetaproteobacteria use Fe(II) oxidation to fuel C fixation, forming the foundation of these deep sea communities. The ‘omics results give insight into electron transport pathways, as well as C, N, and P cycles driven by FeOM. We will also report on the two Zetaproteobacteria strains, CP-5 and CP-8, isolated from the Chesapeake Bay chemocline during seasonal stratification. These strains show some distinct differences in genomic content and biomineral formation that are likely related to their novel planktonic lifestyle. The Zetaproteobacteria in both environments possess a putative Fe oxidase, cyc2, for which function has yet to be proven, so we are working to express and characterize this protein. Finally, we will include comparisons to other known FeOM, including acidophilic and phototrophic FeOM, to give insight into common pathways and evolutionary history of microbial Fe oxidation.<br/>

Fe(II) oxidation by zetaproteobacteria and friends: Mechanisms and influences on biogeochemical cycles

253rd National Meeting (2017)

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