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INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY logo International Journal of Systematic and Evolutionary Microbiology

Volume 75, Issue 11

Isolation of ‘ Ferrigenium straubiae’ – a microaerophilic Fe(II)-oxidizing bacterium and nitrate-reducing Fe(II)-oxidizer within the community of culture KS Open Access

Abstract

‘ Ferrigenium straubiae’ strain KS (KCTC 25982, DSM 118991) is a neutrophilic, Fe(II)-oxidizing bacterium representing up to 98% of the community in culture KS, the most extensively studied mixed culture known for autotrophic nitrate-reducing Fe(II) oxidation. The phylogeny and genome of this bacterium were previously analysed and identified as ‘ Ferrigenium straubiae’. In this study, we report the first-time successful isolation of ‘ Ferrigenium straubiae’ strain KS and its experimental physiological characterization. The bacterium was identified as a non-stalk-forming, rod-shaped and non-halophilic strain with a Gram-negative classification. We characterized its physiology when grown in agarose-stabilized Fe(II)-O gradient tubes where Fe(II) stemming from FeS functions as the electron donor and O as the electron acceptor. It showed growth at temperatures of 20–30 °C (optimal at 25°C) and at pH levels of 6.0–7.5 (optimal at pH 6.5–7.0). The doubling time at 20 °C and pH 6.5 was 16 h. We further optimized the gradient tubes for sustainable culture maintenance using modified Wolfe’s mineral medium (MWMM; 1 g l NHCl) supplemented with 7-vitamin solution, SL-10 trace elements, selenite-tungstate solution and selenite-molybdate-nickel-copper-arsenic-vanadium solution (final concentrations of 10 µM Se, 10 µM Mo, 0.1 µM Ni, 0.1 µM Cu, 0.1 µM As and 5 nM V). We also evaluated several Fe(II) sources (with O as electron acceptor), as well as both inorganic and organic substrates for their influence on growth. Although a known member of the denitrifying community in culture KS, the isolated strain ‘ Ferrigenium straubiae’ KS exhibited exclusively microaerobic and autotrophic growth in agarose-stabilized Fe(II)-O gradients, utilizing Fe(II) from FeS as the electron donor.

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Keyword(s): culture KS , Ferrigenium straubiae , Gallionellaceae , gradient tube , microaerophilic Fe(II) oxidation and nitrate-reducing Fe(II) oxidation
Funding
This study was supported by the:
  • Max-Planck-Gesellschaft
    • Principal Award Recipient: StefanieBecker
  • Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg
    • Principal Award Recipient: NotApplicable
  • Bundesministerium für Bildung und Forschung
    • Principal Award Recipient: NotApplicable
  • Deutsche Forschungsgemeinschaft (Award INST 37/1027-1 FUGG)
    • Principal Award Recipient: NotApplicable
  • Deutsche Forschungsgemeinschaft (Award EXC 2124)
    • Principal Award Recipient: NotApplicable
© 2025 The Authors
  • This is an open-access article distributed under the terms of the Creative Commons Attribution License. This article was made open access via a Publish and Read agreement between the Microbiology Society and the corresponding author’s institution.
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2025-11-17
2025-12-16

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Isolation of ‘Candidatus Ferrigenium straubiae’ – a microaerophilic Fe(II)-oxidizing bacterium and nitrate-reducing Fe(II)-oxidizer within the community of culture KS
Int J Syst Evol Microbiol 75, 006949 (2025); https://doi.org/10.1099/ijsem.0.006949
/content/journal/ijsem/10.1099/ijsem.0.006949
/content/journal/ijsem/10.1099/ijsem.0.006949
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