278 



ORDER III. HYPHOMICROBIALES 



Non-motile. Gram-negative. Colonies are salmon-pink to orange-red in color. Photohetero- 

 trophic. Anaerobic. Found in mud and in fresh water. 

 The type species is Rhodomicrobium vnnnielii Duchow and Douglas. 



1. Rhodomicrobium vannielii Duchow 

 and Douglas, 1949. (Duchow and Douglas, 

 Jour. Bact., 58, 1949, 409; also see Murray 

 and Douglas, Jour. Bact., 59, 1950, 157; 

 and Volk and Pennington, Jour. Bact., 

 59, 1950, 169.) 



van.niel'i.i. M.L. gen. noun vannielii of 

 van Niel; named for C. B. van Niel, an 

 American bacteriologist. 



Mature cells are ovoid, measuring 1.2 by 

 2.8 microns; immature cells are spherical. 

 Non-motile. The cells are connected by 

 filaments which are approximately 0.3 mi- 

 cron in diameter and from one to several 

 times the length of a mature cell. A mature 

 cell may produce as many as three daughter 

 cells: one by formation of a primary fila- 

 ment from the pole of the cell, and one or 

 two more by lateral outgrowths of new fila- 

 ments from the primary filament upon 

 which the first daughter cell is borne. Be- 

 cause of the tendency of the cells to remain 

 attached to the filament, the predominant 

 growth habit is that of an aggregate con- 

 taining many cells. Gram-negative. 



Agar: In shake tubes, colonies are dark 



orange-red, irregular, 2 to 3 mm in diameter 

 and have a rough, convoluted surface. 



Broth: Turbid in young cultures, becom- 

 ing granular and flocculent; salmon -pink 

 to deep orange-red, depending on the den- 

 sity of growth. 



Photoheterotrophic. Cells contain bac- 

 teriochlorophyll and carotenoid pigments. 

 Growth occurs in the presence of light in a 

 mineral medium containing an organic hy- 

 drogen donor and bicarbonate; organic 

 growth factors are not required. Suitable 

 hydrogen donors are ethanol, propanol, 

 butanol, acetate, propionate, butyrate, 

 valerate, caproate, lactate and malate. 



Glucose, mannose, fructose, mannitol, 

 citrate, tartrate, formate, thiosulfate and 

 sulfide are not utilized. 



Anaerobic. 



Optimum temperature, between 25° and 

 30° C. 



Source: Isolated from mud and water 

 from Washington State. 



Habitat: Commonly found in mud, pond, 

 lake and stream waters. 



FAMILY II. PASTEURIACEAE LAURENT, 1890, EMEND. 

 HENRICI AND JOHNSON, 1935. 



(Laurent, Compt. rend. Acad. Sci., Paris, 3, 1890, 754; Henrici and Johnson, 

 Jour. Bact., 30, 1935, 84.) 



Pas.teu.ri.a'ce.ae. M.L. fem.n. Pasteuria type genus of the family; -aceae ending to 

 denote a family; M.L. fem.pl.n. Pasteuriaceae the Pasteuria family. 



Stalked bacteria with spherical or pear-shaped cells; if cells are elongated, the long axis 

 of the cell coincides with the axis of the stalk. Stalks may be very short or absent, but 

 when present they are usually very fine and at times arranged in whorls attached to a 

 common holdfast. Cells multiply by longitudinal fission and/or by budding. Mostly peri- 

 phytic; one species is parasitic. 



The descriptions of the members of this family are largely based upon microscopic exam- 

 inations of collected materials such as parasitized daphnias (fresh-water Crustacea) or 

 glass slides submerged at various depths for about two weeks in Lake Alexander, Minne- 

 sota (Henrici, Jour. Bact., 25, 1932, 277). A few crude cultures were obtained in two liquid 

 media: one containing a mineral solution with precipitated cellulose and ammonium salts 

 as a source of nitrogen, the other being a solution of MgS04 and K2HPO4 in tap water to 



