Gallionella

Abstract Gal.li.o.nel'la. M.L. dim. ending ‐ ella ; M.L. fem. n. Gallionella named for B. Gaillon, a customs agent and zoologist (1782–1839) in Dieppe, France. Gram‐negative, bean‐shaped cells , usually 0.5–0.8 × 1.6–2.5 µm, that secrete an extracellular twisted stalk from the concave side, 0.3–0.5 µm in width and up to 400 µm or more in length. The stalk is composed of numerous 2 nm‐wide fibers and is produced under microaerophilic conditions when cells are in late exponential or stationary growth phase. Motile by means of a polar flagellum. Microaerophilic; chemolithotrophic growth can be obtained in vitro using oxygen and ferrous iron concentration gradients in a salt medium with CO 2 as sole carbon source (Table BXII.β.108). Mixotrophic metabolism has been demonstrated with glucose, fructose, and sucrose. Can be found where anaerobic groundwater with ferrous iron reaches an oxygen‐containing environment. Belongs to the Betaproteobacteria , family Gallionellaceae , with one known species, G. ferruginea . Most closely related species according to 16S rDNA sequence analysis is the chemolithotroph Nitrosospira multiformis , distantly related with a 16S rDNA sequence similarity of 90%. The mol % G + C of the DNA is : 51–54.6 (Hanert, 1989). Type species : Gallionella ferruginea Ehrenberg 1838, 166. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Gallionella is: correct name (last update, February 2025) * . LPSN classification: Bacteria / Pseudomonadati / Pseudomonadota / Betaproteobacteria / Spirillales / Gallionellaceae / Gallionella The genus Gallionella can also be recovered in the Genome Taxonomy Database (GTDB) as g__Gallionella (version v220) ** . GTDB classification: d__Bacteria / p__Pseudomonadota / c__Gammaproteobacteria / o__Burkholderiales / f__Gallionellaceae / g__Gallionella * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: