Novel Fe-oxidizing Zetaproteobacteria floating in the Chesapeake: kinetics and genomic insights into microbial Fe cycling in a stratified marine water column
Abstract
Iron-oxidizing bacteria (FeOB) are potentially important drivers in iron redox cycling, with significant effects on other major elemental cycles (e.g. C, N, P, S, As), yet the biogeochemical impacts of these microbes have been difficult to quantify. FeOB have traditionally been studied in relatively few, Fe-rich environments (groundwater seeps and hydrothermal vents), but our recent studies show that they also occur in coastal marine environments. Here we report on two Zetaproteobacteria strains, CP-5 and CP-8, isolated from the Chesapeake Bay chemocline during seasonal stratification. They represent the first known planktonic chemolithotrophic FeOB and are unusual for living in very low (micromolar) Fe(II) conditions, intermediate (brackish) salinities, and pH values (7.3-7.4) at which abiotic Fe oxidation is typically rapid. However, kinetics experiments demonstrate that CP-8 accelerates iron oxidation, relative to killed controls, and allow us to quantify the effects of microbes on iron oxidation. Ongoing work is characterizing the O2 preferences of the CP strains, specifically the lower O2 limits of FeOB activity. We obtained complete, closed genomes of both CP-5 and CP-8 genomes (2.54 and 2.30 Mbp respectively) using the PacBio RSII sequencer. Our genomic analysis of the CP strains is focused on adaptations for growth in the Chesapeake Bay chemocline, including genes for energy metabolism, and C, N, and P cycling. Initial results indicate that both strains have putative iron oxidase Cyc2 as well as Rubisco which suggests that these microbes are using energy from Fe oxidation to fix carbon, despite the availability of organics from phototrophs living higher in the water column. Our work on these Chesapeake FeOB gives us insight into how chemolithotrophic FeOB can participate in Fe redox and nutrient cycling in a stratified marine water column.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B11F0526C
- Keywords:
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- 0419 Biomineralization;
- BIOGEOSCIENCESDE: 1039 Alteration and weathering processes;
- GEOCHEMISTRYDE: 1040 Radiogenic isotope geochemistry;
- GEOCHEMISTRYDE: 1041 Stable isotope geochemistry;
- GEOCHEMISTRY