ORDEE CHLAMYDOBACTERIALES 981 



ORDER III. CHLAMYDOBACTERIALES BUCHANAN. 



(Jour. Bact., 2, 1917, 162.) 



Filamentous, colorless, alga-like bacteria. May or may not be ensheathed. 

 They may be unbranched or may show false branching. False branching arises from 

 a lateral displacement of the cells of the filament within the sheath which gives rise 

 to a new filament, so that the sheath is branched while the filaments are separate. 

 The sheath may be composed entirely of iron hydroxide, or of an organic matrix 

 impregnated ^^'\\\\ iron, or may be entirely organic. The filaments themselves may 

 show motility by a gliding movement like that found in the blue-green algae (OsciUa- 

 loriaceae). Conidia and motile flagellate swarm cells may be developed, but never 

 endospores. Fresh water and marine forms. 



Key to the families of order Chlamydobacteriales.* 



I. Alga-like filaments which do not contain sulfur globules. False branching may 

 occur. 



A. Usually free floating filaments. ^Motile swarm cells may be formed. 



Family I. Chlamydohaeteriaceae, p. 981. 



B. Attached filaments which show a differentiation of base and tip. Xon-molile 



conidia formed in the swollen tips of the filaments. 



Family II. Crenothrichaceae , p. 987. 

 II. Alga-like, unbranching filaments which maj- contain sulfur globules when growing 

 in the presence of sulfides. Filaments may be motile by a creeping or sliding 

 movement along a solid substrate. 



Family III. Bcggiatoaceae, p. 988. 



FAMILY I. CHLAMYDOBACTERIACEAE MIGULA.** 



(Arb. Bakt. Inst. Hochschule, Karlsruhe, 1, 1894, 237.) 



Filamentous bacteria which frequently show false branching. Sheaths may or 

 may not be impregnated with ferric h3'droxide. Cells divide only transversely. 

 Swarm cells, it developed, are usualh' motile by means of flagella. Usually found 

 in fresh water. 



Key to the genera of family Chlamydobacteriaceae. 



I. Showing typical false branching. 



A. Sheaths entirely organic, not impregnated with ferric hydroxide. 



Genus I. Sphaerotilus, p. 982. 



B. Sheaths impregnated with ferric hydroxide. 



Genus II. Clonothrix, p. 983. 

 II. Unbranched or rarely showing false branching. 



A. Sheaths or holdfasts impregnated with ferric hydro.xide. 



Genus III. Leptothrix, p. 983. 



* In Appendix I, p. 996, will be found a group of non-filamentous, non-sheath- 

 forming, colorless sulfur bacteria, as the family Achromatiaceae . Their true rela- 

 tionships are as yet obscure, and they have been attached as an Appendix to the 

 Chlamydobacteriales largeh' on account of the similarity of their metabolism to that 

 of the Bcggiatoaceae. 



** Completely revised by Prof. A. T. Henrici, University of Minnesota, Minneap- 

 olis, Minnesota, December, 1938; further revision by Prof. Robert S. Breed, Xew 

 York State Experiment Station, Geneva, New York, July, 1946. 



