RESEARCH ARTICLE Hidden in plain sight: discovery of sheath-forming, iron-oxidizing Zetaproteobacteria at Loihi Seamount, Hawaii, USA Emily J. Fleming1, Richard E. Davis2, Sean M. McAllister3,, Clara S. Chan4, Craig L. Moyer3, Bradley M. Tebo2 & David Emerson1 1Bigelow Laboratory for Ocean Sciences, East Boothbay, ME, USA; 2Department of Environmental and Biomolecular Systems, Oregon Health and Science University, Portland, OR, USA; 3Department of Biology, Western Washington University, Bellingham, WA, USA and 4Department of Geological Sciences, University of Delaware, Newark, DE, USA Correspondence: David Emerson, Bigelow Abstract Laboratory for Ocean Sciences, PO Box 380, East Boothbay, ME 04544, USA. Tel.: +1 207 Lithotrophic iron-oxidizing bacteria (FeOB) form microbial mats at focused 315 2567; fax: +1 207 315 2329; flow or diffuse flow vents in deep-sea hydrothermal systems where Fe(II) is a e-mail:
[email protected] dominant electron donor. These mats composed of biogenically formed Fe(III)-oxyhydroxides include twisted stalks and tubular sheaths, with sheaths Present address: Sean M. McAllister, typically composing a minor component of bulk mats. The micron diameter Department of Geological Sciences, Fe(III)-oxyhydroxide-containing tubular sheaths bear a strong resemblance to University of Delaware, Newark, DE, USA sheaths formed by the freshwater FeOB, Leptothrix ochracea. We discovered that Received 20 December 2012; revised 28 veil-like surface layers present in iron-mats at the Loihi Seamount were domi- – February 2013; accepted 28 February 2013. nated by sheaths (40 60% of total morphotypes present) compared with deeper Final version published online 15 April 2013. (> 1 cm) mat samples (0–16% sheath). By light microscopy, these sheaths appeared nearly identical to those of L.