264 



ORDER II. CHLAMYDOBACTERIALES 



ent. The sheaths become brittle and glass- 

 like in appearance by deposition of ferric 

 hj^droxide in a hard colloidal form. Prings- 

 heim (Endeavour, 11, 1952, 209) states that 

 under these conditions it is identical with 

 Leptothrix ochracea, which looks ochre-like 

 in bulk but never brown under the micro- 

 scope. 



Source: Originally found in polluted 

 waters. May become a real nuisance in 

 sewage purification plants of the activated 

 sludge type (Lackey and Wattie, op. cit., 

 1940, 975) and in streams polluted with sul- 

 fite liquor from pulp and paper mills 

 (Lackey, Mimeographed Rept., U. S. 

 Pub. Health Ser., 1941). 



Habitat: Stagnant and running water, 

 especially sewage-polluted streams. Widely 

 distributed throughout the world in fresh 

 water. 



2. Sphaerotilus dichotonius (Cohn, 

 1875) Migula, 1900. (Cladothrix dichotoma 

 Cohn, Beitr. z. Biol. d. Pflanz., 1, Heft 3, 

 1875, 185; Migula, Syst. d. Bakt., 2, 1900, 

 1033.) 



di.cho'to.mus. Gr. adj. dichotomus di- 

 vided, forked. 



The identity of this species as distinct 

 from Sphaerotilus natans has been ques- 

 tioned. In his text, Cohn reports the di- 

 ameter of the trichomes to be 0.3 micron. 

 This clearly is an error as his figures at 



600X show the diameter of the trichomes to 

 be greater than the diameter of Bacillus 

 anthracis spores shown at the same mag- 

 nification. Such spores are 1.3 to 1.5 microns 

 in diameter. 



Zikes (Cent. f. Bakt., II Abt., 43, 1915, 

 529) gives the following differential charac- 

 ters : Cells smaller than those of Sphaerotilus 

 natans, 1.5 to 2.5 microns; false branching 

 constant; grows best in high concentrations 

 of meat extract; will grow in ordinary pep- 

 tone solutions; can utilize inorganic nitro- 

 gen; liquefies gelatin slowly. 



Source: Isolated by Cohn from water con- 

 taining Myconostoc. 



Habitat: Comparatively unpolluted fresh 

 water capable of sustaining algae. 



3. Sphaerotilus flviitans (Migula, 1895) 

 Schikora, 1899. {Streptothrixfluitans Migula, 

 in Engler and Prantl, Die natiirl. Pflanzen- 

 fam., 1, la, 1895, 38; Schikora, Ztschr. f. 

 Fischerei, 7, 1899, 1-28.) 



flu'i.tans. L. part. adj. fluitans floating. 



Verj thin, attached trichomes as much as 

 1 cm in length. The trichomes are sur- 

 rounded by a soft sheath from which almost 

 spherical conidia issue, usually attaching 

 themselves to the exterior of the sheath 

 where they multiply. 



Source: Found attached to pieces of wood 

 and stems of plants in running water. 



Habitat: Fresh water. 



Genus II. Leptothrix Kiitzing, 1843. 



(Kiitzing, Phycologia Generalis, 1843, 198; not Leptotrichia Trevisan, Reale 

 1st. Lombardo di Sci. e Lettere, Ser. 2, 12, 1879, 138.) 



Lep'to.thrix. Gr. adj. leptus fine, small; Gr. noun thrix hair; M.L. fem.n. Leptothrix fine 

 hair. 



Trichomes of cylindrical, colorless cells with a sheath at first thin and colorless, later 

 thicker, yellow or brown, encrusted with iron or manganese oxide. The oxides may be dis- 

 solved by dilute acid, whereupon the inner cells show up well. If the sheath contains man- 

 ganese oxide, it does not dissolve completel}^ in weak acids. When examined under the elec- 

 tron microscope, the sheath shows an alveolar structure. Multiplication is by cell division 

 with individual cells occasionally slipping out of the sheath as reproductive cells. These 

 are sometimes motile with a tuft of flagella. False branching may occur. Gram-negative and 

 not acid-fast so far as known. Usually found in fresh water. 



The type species is Leptothrix ochracea Kiitzing. 



Key to the species of genus Leptothrix. 



I. Trichomes straight, not spirally twisted. 



A. Trichomes free-floating and unbranched. Sheath thin. 



