FAMILY I. HYPHOMICROBIACEAE 



277 



II. Photoheterotrophic. Non-motile. 



Genus II. Rhodomicrohium, p. 277. 



Genus I. Hyphomicrobium Stutzer and Hartleb, 1898. 



(Mitteil. d. landwirtsch. Inst. d. k. Univ. Breslau, 1898; abst. in Cent. f. Bakt., II Abt., 



6, 1899, 678.) 



Hy.pho.mi.cro'bi.um. Gr. noun hyphe thread; Gr. adj. micrus small; Gr. noun hius life; 

 M.L. neut.n. Hyphomicrobium thread (-producing) microbe. 



Daughter cells may remain attached to the filaments which connect them to the mother 

 cells or may tear free of the filament as the result of active movement by means of a single, 

 polar flagellum. Gram-negative. Non-pigmented. Metabolism is chemoheterotrophic and 

 oxidative. Aerobic. Found in soil and in fresh water. 



The type species is Hyphomicrobium vulgare Stutzer and Hartleb. 



1. Hyphomicrobium vulgare Stutzer 

 and Hartleb, 1898. (Saltpeterpilz, Stutzer 

 and Hartleb, Cent. f. Bakt., II Abt., 3, 

 1897, 621; Stutzer and Hartleb, Mitteil. d. 

 landwirtsch. Inst. d. k. Univ. Breslau, 1898; 

 abst. in Cent. f. Bakt., II Abt., 5, 1899, 

 678.) 



vul.ga're. L. adj. vxdgaris common. 



Description taken from Stutzer and 

 Hartleb {loc. cit.), Kingma-Boltjes (Arch, 

 f. Mikrobiol., 7, 1936, 188) and Mevius 

 (Arch. f. Mikrobiol., 19, 1953, 1). 



Mature cells are ovoid, measuring 0.5 

 by 1.0 nucron; immature cells are spherical. 

 Motile bj- means of a single, polar flagel- 

 lum. Daughter cells are borne on filaments 

 measuring approximately 0.2 micron or 

 less in diameter and varying in length from 

 one to several times the length of mature 

 cells. The predominant growth habit is that 

 of a dense clump of cells from which fila- 

 ments radiate outward. Branching of the 

 filament occurs but is not common. 

 Daughter cells may tear free of the fila- 

 ments and e.xist as single, motile cells with 

 motility sometimes persisting even after 

 the cell has produced a filament of consid- 

 erable length. Cells in pairs, connected 

 by a filament, are common. Gram-nega- 

 tive. 



Gelatin: No growth. 



Formate-nitrate agar or silica gel plates: 

 Colonies are colorless, 0.5 to 1.0 mm in di- 

 ameter, slightly elevated, entire. 



Peptone agar colonies: Much smaller 

 than those above. 



Peptone broth: Poor growth. 



Formate-nitrate broth: Growth occurs 

 as a light, cream-colored, granular sedi- 

 ment. 



Chemoheterotrophic, oxidative. Growth 

 occurs in mineral media at pH 7.0 to 7.5 

 with ammonium or nitrate as a nitrogen 

 source and formate, formaldehyde, meth- 

 anol, acetate or lactate as a carbon source. 

 Some growth occurs in mineral media with- 

 out an added carbon source at the expense 

 of organic compounds in the air. 



Sucrose not attacked. 



Asparagine not utilized. 



Aerobic. 



Temperature range for growth, 20° to 

 37° C. 



Source: Isolated from soil and water. 

 Commonly found in enrichment cultures 

 for nitrifying bacteria and in activated 

 sludge. Babudieri (Rendiconti Istit. Super, 

 di Sanita, Roma, 13, 1950, 589) has found 

 this species as a contaminant in Leptospira 

 canicola cultures. 



Habitat: Widely distributed in soil and 

 in fresh water. 



Genus II. Rhodomicrobium Duchow and Douglas, 1949. 



(Jour. Bact., 58, 1949, 409.) 



Rho.do.mi.cro'bi.um. Gr. noun rhodum the rose; Gr. adj. micrus small; Gr. noun bius 

 life; M.L. neut.n. Rhodomicrobium red (-producing) microbe. 

 The daughter cells remain attached to the filaments connecting them to the mother cells. 



