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.
