Deep-sea hydrothermal vents are a significant source of oceanic iron. Although hydrothermal iron rapidly precipitates as inorganic minerals on mixing with seawater, it can be stabilized by organic matter and dispersed more widely than previously recognized. The nature and source of this organic matter is unknown. Here we show that microbial genes involved in cellular iron uptake are highly expressed in the Guaymas Basin deep-sea hydrothermal plume. The nature of these microbial iron transporters, taken together with the low concentration of dissolved iron and abundance of particulate iron in the plume, indicates that iron minerals are the target for this microbial scavenging and uptake. Our findings indicate that cellular iron uptake is a major process in plume microbial communities and suggest new mechanisms for generating Fe-C complexes. This 'microbial iron pump' could represent an important mode of converting hydrothermal iron into bioavailable forms that can be dispersed throughout the oceans.
Bibliographical noteFunding Information:
This project is funded by the Gordon and Betty Moore Foundation through grant GBMF 2609 to G.J.D./J.A.B./B.M.T. and by the National Science Foundation through grants OCE 1029242 to G.J.D., and R2K grant OCE1038055/1037991/1038006 to J.A.B./B.M.T./ G.J.D. We thank N. Jiao, K. Tang and M. Chen at Xiamen University for assistance with TonB gene functional analysis and B. Hopkinson at University of Georgia for providing iron transporter sequences. We thank S. Jain at University of Michigan for assistance with bioinformatic analysis. We thank G. Cody (Geophysical Laboratory) and S. Myneni (Princeton University) for discussions regarding STXM data. We thank M. Marcus, S. Fakra and D. Kilcoyne for synchrotron support at the Advanced Light Source (BLs 10.3.2 and 220.127.116.11), and S. Bennett and J. Sorensen for assistance in synchrotron data collection. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231. M. Tsz-ki Tsui (University of North Carolina at Greensboro) and members of Geomicrobiology lab at University of Michigan provided helpful comments and revisions to the manuscript.