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Front. Microbiol. | doi: 10.3389/fmicb.2018.02808

Diversity of iron oxidizers in groundwater-fed rapid sand filters: Evidence of Fe(II)-dependent growth by Curvibacter and Undibacterium spp.

  • 1Harvard University, United States
  • 2Technical University of Denmark, Denmark
  • 3Istanbul Technical University, Turkey
  • 4Danish Technological Institute (DTI), Denmark

Although earlier circumstantial observations have suggested the presence of iron oxidizing bacteria (IOB) in groundwater-fed rapid sand filters (RSF), ferrous iron (Fe(II)) oxidation in this environment is often considered a chemical process due to the highly oxic and circumneutral pH conditions. Due to the low water temperature (5–10°C), typical of groundwaters, on the other hand, rates of chemical Fe(II) oxidation may be reduced, which may allow IOB to grow and compete with chemical Fe(II) oxidation. Hence, we hypothesized that IOB are active and abundant in groundwater-fed RSFs. Here, we applied a combination of cultivation and molecular techniques to isolate, quantify, and confirm the growth of IOB from groundwater-fed rapid sand filters, operated at different influent Fe(II) concentrations. Isolates related to Undibacterium and Curvibacter were identified as novel lineages of IOB. Gallionella spp. were dominant in all waterworks, whereas Ferriphaselus and Undibacterium were dominant at pre-filters of those receiving groundwaters with high (>2 mg/l) Fe(II) concentrations. The high density and diversity of IOB in groundwater-fed RSFs suggest that neutrophilic iron oxidizers may not be limited to oxic/anoxic interfaces.

Keywords: iron oxidizing bacteria, novel, Rapid sand filters, Curvibacter, Undibacterium, iron metabolism, Ferriphaselus, Gallionella

Received: 21 Aug 2018; Accepted: 31 Oct 2018.

Edited by:

David Emerson, Bigelow Laboratory For Ocean Sciences, United States

Reviewed by:

Dirk De Beer, Max-Planck-Gesellschaft (MPG), Germany
Anirban Chakraborty, University of Calgary, Canada  

Copyright: © 2018 Gülay, Çekiç, Musovic, Albrechtsen and Smets. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Dr. Arda Gülay, Harvard University, Cambridge, United States, ardagulay@gmail.com
Prof. Barth F. Smets, Technical University of Denmark, Kongens Lyngby, 2800 Kgs, Denmark, bfsm@env.dtu.dk