FAMILY V. CAULOBACTERACEAE 213 



by ZoBell and Allen (Proc. Soc. Exper. Biol, and Med., 30, 1933, 1409) has proved to be 

 most useful for studying bacteria that live attached to a substrate. 



The species included in Pasteuria Metchnikoff and Blaslocmdis Henrici and Johnson 

 reproduce by a curious form of fission or budding. They have been transferred to a new- 

 Order, Hyphomicrobiales Douglas. 



Key to the genera of family Caulobacteraceae. 



I. Long axis of cell coincides with axis of stalk. Stalks slender. 



Genus I. Caulobacter , p. 213. 

 II. Long axis of cell transverse to long axis of stalk. Stalks may be twisted and branched. 



A. Stalks are band-shaped or rounded. Contain ferric hydroxide. 



1. Stalks band-shaped and twisted. Dumb-bell-shaped in cross section. 



Genus II. Gallionella, p. 214. 



2. Stalks horn-shaped, not twisted. Round in cross section. 



Genus III. Siderophacus, p. 216. 



B. Stalks lobose, composed of gum. Forming zoogloea-like colonies. Free-floating. 



Genus IV. Nevskia, p. 216. 



Genus I. Caulobacter Henrici and Johnson, 1935. 

 (Jour. Bact., 29, 1935, 4; ihid., 30, 1935, 83.) 



Cau.lo.bac'ter. L. noun caxdis a plant stem or stalk; M.L. noun bader masculine form of 

 Gr. neut.n. bactrum a rod; M.L. mas.n. Caulobacter stalk rod. 



Stalked, curved, rod-shaped bacteria, the long axis of the elongated cells coinciding with 

 the long axis of the stalks. Young cells motile by means of a single polar flagellum. Old cells 

 attached to submerged objects by a stalk that is a continuation of the cell. A holdfast is de- 

 veloped at the distal end. Multiplication of cells is by transverse binary fission. Periphytic, 

 growing upon submerged surfaces. 



The type species is Caulobacter vibrioides Henrici and Johnson emend. Bowers et al. 



1. Caulobacter vibrioides Henrici and Agar colonies: Surface colonies up to 5 

 Johnson, 1935, emend. Bowers et al., 1954. mm in diameter, round, smooth, slightly 

 (Henrici and Johnson, Jour. Bact., 30, 1935, raised, glistening, finely granular in the 

 83; Bowers, Weaver, Grula and Edwards, center, grayish white, with center and re- 

 Jour. Bact., 68, 1954, 194.) verse side becoming brownish yellow. Sub- 



vib.ri.oi'des. L.v. vibro to vibrate; M.L. surface colonies dense, brownish yellow, 



noun Vibrio name of a genus; Gr. noun lenticular, up to 0.5 mm in diameter and 1.0 



eidus shape, form; M.L. adj. vibrioides re- mm in length, 



sembling a vibrio. Agar slant: Growth filiform, grayish 



Cells elongated, curved, vibrio-like, with white, glistening, viscid, 



rounded ends, 0.5 to 1.2 by 1.5 to 3.0 mi- Broth: Moderate turbidity with slightly 



crons; filamentous forms occasionally pro- viscid sediment, 



duced. Young cells actively motile with a Litmus milk: Unchanged, 



single polar flagellum; older cells develop p^^^^^^ kittle or no growth, 

 a stalk at the flagellated end. The stalk has 

 a central filament or tube and a membrane 

 that is continuous with the cell wall. Organ- 

 isms attached singly or in rosettes, with 



Indole not produced. 



Nitrites not produced from nitrates. 



No acid or gas from carbohydrates. 



stalks attached to a common holdfast. Usu- Requires riboflavin, phosphates, iron and 



ally surrounded by a slime layer. Gram- an organic source of energy for growth. Glu- 



negative. 



cose, maltose or casamino acids are used as 



Gelatin: Surface growth and filiform sources of carbon and energy; sodium bi- 

 growth in stab without liquefaction. carbonate, sodium lactate, sodium acetate 



