214 ORDER I. PSEUDOMONADALES 



or glycerol not utilized. Ammonium sulfate ander, Minnesota, and other fresh-water 

 or casamino acids used as sources of nitro- lakes (Henrici and Johnson, op. cit., 30, 

 gen; ammonium nitrate not utilized. 1935, 83). Also found in well-water in Ken- 

 Optimum temperature, 30° C. tucky (Bowers et al., op. cit.). 

 Aerobic, facultative. Habitat: Water, where it grows upon firm 

 Source: Found frequently in Lake Alex- substrates.* 



Genus II. Gallionella Ehrenberg, 1838.-f 



(Ehrenberg, Die Infusionsthierchen, 1838, 166; not Gaillonella Bory de St. Vincent, Diet. 



Classique d'Hist. Nat., 4, 1823, 393; Didymohelix Griffith, Ann. 



Mag. Nat. Hist., Ser. 2, 12, 1853, 438.) 



Gal.li.o.nel'la. Named for Benjamin Gaillon, receiver of customs and zoologist (1782- 

 1839) in Dieppe, France; M.L. dim. ending -ella; M.L. fem.n. Gallionella a generic name. 



Cells kidney-shaped or rounded. Placed at the end of the stalk with the long axis of the 

 cell transverse to the long axis of the stalk. Stalks secreted by the cells are slender and 

 twisted. Branch dichotomously or in the form of umbels. Stalks more or less dumb-bell or 

 bisquit-shaped in cross section. Composed of ferric hydroxide, completely dissolving in 

 weak acids. Two polar flagella are present when the cells are motile. Gram-negative. Multi- 

 plication by fission of the cells, the daughter cells remaining at first at the end of the stalk; 

 later they may be liberated as swarm cells. Grow only in iron-bearing waters. Do not store 

 manganese compounds. From both fresh and salt water. When the first species was discov- 

 ered the twisted stalks were thought to be a chain of diatoms. 



The type species is Gallionella ferruginea Ehrenberg. 



Key to the species of genus Gallionella. 



I. Stalks branched. 



A. Stalks dichotomously branched. 

 1. Stalks slender, spirally twisted, 

 a. Cells small, stalks very slender. 



1. Gallionella ferruginea. 



* The papers by Houwink (Antonie van Leeuwenhoek, 21, 1955, 29) and by Kandler, 

 Zehender and Huber (Arch. f. Mikrobiol., 21, 1954, 57) were received after the manuscript 

 covering the family Caulobacteraceae was prepared. They give further information regard- 

 ing the structure and function of the stalk of Caulobacter sp. Clearly the stalks developed 

 by species in this genus are quite different in nature from the stalks of ferric hydroxide or 

 gum secreted by the cells of other species placed in other genera of this family. 



t Gallionella Ehrenberg is accepted and is continued in use in this edition of the Manual 

 although under a strict interpretation of Rules of Nomenclature it should apparently be 

 regarded as a homonym and therefore illegitimate. Gaillonella Bory de St. Vincent, proposed 

 as the name of a genus of algae, appears to have priority (see Internat. Bull. Bact. Nomen. 

 and Tax., 2, 1951, 96). However, Gaillonella B. de St. V. is no longer used by students of 

 diatoms so that Gallionella E. may be retained as a gemis conservandum in bacteriology with- 

 out causing confusion. Unless Gallionella E. is retained, the little used Didymohelix Griffith 

 must be again introduced into the Manual with the formation of a series of new combina- 

 tions. 



The situation is complicated because the final settlement of this problem of nomenclature 

 requires action both by the Judicial Commission of the International Association of Micro- 

 biologists and the Special Committee on Diatomaceae of the International Botanical Con- 

 gress. The majority of the special students of iron bacteria have accepted and used Gallion- 

 ella E., e.g. Molisch (1910), Naumann (1921), Cholodny (1924), Butkevich (1928), Dorff 

 (1934), Henrici and Johnson (1934), Beger (1941) and Pringsheim (1952). 



