The family Gallionellaceae
Book chapter, 2013
© 2014 Springer-Verlag Berlin Heidelberg. All rights reserved. The family Gallionellaceae comprises the genus Gallionella with one established type species, Gallionella ferruginea. The phylogenetic position of Gallionellaceae, as determined by 16S-rDNA sequence comparisons, is among the β-proteobacteria. Its phylogenetic neighbors are Methylophilaceae, Nitrosomonadaceae, and Spirillaceae. The family contains gram-negative, chemolithoautotrophic, neutrophilic, and aerobic ferrous iron-oxidizing bacteria with the ability to secrete an extracellular twisted stalk composed of numerous fibers. Gallionellaceae can be found where anaerobic groundwater containing ferrous iron reaches an environment that contains oxygen. Large amounts of stalk material are usually produced; this material attracts iron hydroxides and many trace metals, giving it a brown, macroscopic appearance. The stalk and iron hydroxide masses formed may eventually cause severe clogging of ditches, drinking-water wells, and any other facilities utilizing iron-bearing, anaerobic groundwater. The family is relevant to biotechnological processes, as it can be used to remove ferrous iron when producing drinking water from groundwater.