Iron-oxidizing bacterium
Gallionella
Gallionella is a genus of kidney-shaped, iron-oxidizing bacteria primarily found in iron-rich groundwater and surface waters. They are renowned for producing extracellular, twisted stalks composed of ferric hydroxide. These bacteria are chemolithotrophic, deriving energy from the oxidation of ferrous iron to ferric iron under microaerophilic conditions. Their presence often leads to the formation of ochre-colored deposits in wells and springs.
Details
Identification
Kidney-shaped cells; characteristic twisted, ribbon-like stalks made of ferric hydroxide; formation of ochre-colored precipitates.
Social behavior
Formation of biofilms and filamentous colonies through extracellular stalks.
Diet
Chemolithotrophic; utilizes the oxidation of Fe(II) to Fe(III) as an energy source and fixes CO2 as a carbon source.
Overwintering
Persistence in sediments and biofilms.
Ecology
Ecological role
Significant role in the global iron cycle; contributes to the formation of iron deposits and biological ochre.
Natural predators
Protozoa (unicellular organisms) that graze on bacteria.
Competitor species
Other iron-oxidizing bacteria such as Leptothrix.
Ecosystem service
Biological iron removal from water; involvement in the formation of mineral resources.
Threats
Excessive oxygen saturation of water; extreme pH fluctuations.
Scientific profile
Profile
Habitat
Iron-rich, low-oxygen groundwater, wells, drainage systems, springs, and mine drainage. Prefers the redox interface (oxycline) where Fe(II) and low concentrations of O2 (0.1–1.0 mg/L) coexist.
Ecological role
Key organism in the global iron cycle; contributes significantly to the biomineralization of iron oxides. In technical systems (wells), its activity leads to 'ochre formation' (biofouling), reducing hydraulic conductivity.