Recognition of the Iron Bacteria “Siderocapsa” as Arthrobacters and Description of Arthrobacter siderocapsulatus sp.nov.

For the first time strains of Siderocapsa eusphaera Skuja, A and G, have been obtained in pure culture from lake water. The morphological variation of these strains exceeds the species distinctions of the previously described members of the genus Siderocapsa and those of the closely related and little studied other members of the family Siderocapsaceae, such as Siderobacter Naumann, Sideromonas Cholodny, Sideronema Berger, Ferribacterium Brusoff. Studies of the developmental cycle and physiology have shown that the newly isolated, Siderocapsa-like bacteria belong to the genus Arthrobacter of the family Corynebacteriaceae Cohn and Dimmick. The type species of this genus, Arthrobacter globiformis, and also the species A. citreus and A. simplex have been shown to be capable of oxidizing manganese and iron, thus forming morphological structures characteristic of Siderocapsaceae. It is proposed, therefore, that the family Siderocapsaceae be abolished as an independent taxonomic entity and that the naturally occurring bacteria so far described as species of Siderocapsa be considered growth forms of Arthrobacter species developing under specific conditions of habitat. Strains A and G of Arthrobacter (Siderocapsa) are regarded as belonging to a new species for which the name Arthrobacter siderocapsulatus is proposed. The strains have been deposited in the All-Union Collection of Microorganisms and have been assigned the numbers BKM-B N 1122 and BKM-B N 1123, respectively. Strain BKM-B N 1122 is designated as the type strain of A. siderocapsulatus.