Growth very abundant, spreading over the entire surface; iridescent. Peptone and manganese acetate broth: Abundant growth in the form of loose fiakes. Indole not produced. Hydrogen sulfide not produced. Acetylmethylcarbinol not produced. Nitrites produced from nitrates. Optimum temperature, 28° C. Optimum pH, 8.0. Aerobic, but growth favored by the pres- ence of CO2 . Habitat: Found in iron-bearing, fresh waters; widely distributed.
2. Leptothrix thermalis (Molisch, 1925) Dorff, 1934. (Chlamydothrix thermalis Mo- lisch, Sc. Rept. Tohoku Imp. Univ., 4 ser. Biol., Sendae, Japan, 1, 1923, 135 (or pos- sibly 1, 1925, 146); Dorff, Die Eisenorganis- men, Pflanzenforschung, Heft 16, 1934, 38.) ther.ma'lis. Gr. noun therme heat; M.L. adj. thermalis pertaining to heat. Unbranched trichomes, 0.4 to 0.5 micron thick, united in bundles. Surrounded by a sheath which may store iron and turn brown. Source : From warm and hot spring waters in Japan. Habitat: Found in warm and hot (37° to 74° C.) spring waters.
3. Leptothrix sideropous (Molisch, 1910) Cholodny, 1926. {Chlamydothrix sider- opous Molisch, Die Eisenbakterien, 1910, 14; Cholodny, Die Eisenbakterien, Pflanzen- forschung, Heft 4, 1926, 25.) si.de'ro.pous. Gr. adj. sideropus or sideropous iron-footed. Description taken from Molisch {op. cit. 1910, 14) and Cataldi (Estudio Fisiologico y Sistemdtico de Algunas Chlamydobac teriales. Thesis, University of Buenos Aires 1939, 62 and 66). Cells rod-shaped, 0.5 to 0.8 micron Motile. Trichomes short and unbranched Sheath very thin and colorless, giving an iron reaction only at the base of the tri chome. Attached by a broad holdfast which gives a marked iron reaction. Not acid-fast. Gram-negative. Gelatin: No liquefaction. Iron citrate and ammonium agar colonies : Very filamentous. Colonies and filaments encompassed by a spattering of rust-colored spots. Manganese acetate agar colonies: Large and filamentous, the filaments being strongly colored. Iron citrate and ammonium agar slant: Growth in the form of isolated colonies; strongly colored. Manganese acetate agar slant: Abundant growth which adheres to the medium except in those places covered with water of con- densation. Peptone and manganese acetate broth: Firm pellicle with a metallic sheen. Indole not produced. Hydrogen sulfide not produced. Acetylmethylcarbinol not produced. Nitrites produced from nitrates. Optimum temperature, between 25° and 28° C. Optimum pH, 8.0. Aerobic; growth not favored by the pres- ence of CO2 . Habitat: Found growing on the surfaces of objects submerged in water; widely dis- tributed.
4. Leptothrix discophora (Schwers, 1912) Dorff, 1934. (Megalothrix discophora Schwers, Cent. f. Bakt., II Abt., 33, 1912, 273; Leptothrix crassa Cholodny, Cent. f. Bakt., II Abt., 61, 1924, 292; Dorff, Die Eisenorganismen, Pflanzenforschung, Heft 16, 1934, 31.) dis.co'pho.ra. Gr. noun discus a disc; Gr. adj. phorus bearing; M.L. adj. discophorus disc-bearing. Description taken from Schwers (op. cit., 1912, 273) and Cataldi (Estudio Fisiologico y Sistemdtico de Algunas Chlamydobac- teriales. Thesis, University of Buenos Aires, 1939, 60 and 66). Cells 0.5 by 0.8 micron. Motile. Tri- chomes long, slender, articulated, composed of elements of varjdng length showing false branching (Cholodny, Cent. f. Bakt., II Abt., 61, 1924, 297). Usually attached to a submerged substrate, but may be free- floating. A sheath, thick (10 to 15 microns) at the base, tapering toward the free tip
