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Medientyp:
E-Artikel
Titel:
Enhanced Growth of Acidovorax sp. Strain 2AN during Nitrate-Dependent Fe(II) Oxidation in Batch and Continuous-Flow Systems
Beteiligte:
Chakraborty, Anirban;
Roden, Eric E.;
Schieber, Jürgen;
Picardal, Flynn
Erschienen:
American Society for Microbiology, 2011
Erschienen in:
Applied and Environmental Microbiology, 77 (2011) 24, Seite 8548-8556
Sprache:
Englisch
DOI:
10.1128/aem.06214-11
ISSN:
0099-2240;
1098-5336
Entstehung:
Anmerkungen:
Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Microbial nitrate-dependent, Fe(II) oxidation (NDFO) is a ubiquitous biogeochemical process in anoxic sediments. Since most microorganisms that can oxidize Fe(II) with nitrate require an additional organic substrate for growth or sustained Fe(II) oxidation, the energetic benefits of NDFO are unclear. The process may also be self-limiting in batch cultures due to formation of Fe-oxide cell encrustations. We hypothesized that NDFO provides energetic benefits via a mixotrophic physiology in environments where cells encounter very low substrate concentrations, thereby minimizing cell encrustations.
<jats:named-content content-type="genus-species">Acidovorax</jats:named-content>
sp. strain 2AN was incubated in anoxic batch reactors in a defined medium containing 5 to 6 mM NO
<jats:sub arrange="stagger">3</jats:sub>
<jats:sup arrange="stagger">−</jats:sup>
, 8 to 9 mM Fe
<jats:sup>2+</jats:sup>
, and 1.5 mM acetate. Almost 90% of the Fe(II) was oxidized within 7 days with concomitant reduction of nitrate and complete consumption of acetate. Batch-grown cells became heavily encrusted with Fe(III) oxyhydroxides, lost motility, and formed aggregates. Encrusted cells could neither oxidize more Fe(II) nor utilize further acetate additions. In similar experiments with chelated iron (Fe(II)-EDTA), encrusted cells were not produced, and further additions of acetate and Fe(II)-EDTA could be oxidized. Experiments using a novel, continuous-flow culture system with low concentrations of substrate, e.g., 100 μM NO
<jats:sub arrange="stagger">3</jats:sub>
<jats:sup arrange="stagger">−</jats:sup>
, 20 μM acetate, and 50 to 250 μM Fe
<jats:sup>2+</jats:sup>
, showed that the growth yield of
<jats:named-content content-type="genus-species">Acidovorax</jats:named-content>
sp. strain 2AN was always greater in the presence of Fe(II) than in its absence, and electron microscopy showed that encrustation was minimized. Our results provide evidence that, under environmentally relevant concentrations of substrates, NDFO can enhance growth without the formation of growth-limiting cell encrustations.
</jats:p>