CLASS II. SCHIZOMYCETES VON NAEGELI, 1857. 



(Von Naegeli, Bericht Verhandl. d. bot. Section d. 33 Versammling deutsch. Naturfonsch. 

 u. Arzt. Bot. Ztg., 1857, 760; Bacterien, Cohn, Beitr. z. Biol. d. Pflanzen, /, Heft 2, 1872, 

 127; Bacteriaceae Cohn, Arch. f. path. Anat., 55, 1872, 237; Schizomijcetaceae DeToni and 

 Trevisan, in Saccardo, Sylloge Fungorum, 8, 1889, 923; Bacteriales Clements (as an ordinal 

 name), The Genera of Fungi, Minneapolis, 1909, 8; Schizomycetacea Castellani and Chal- 

 mers, Manual of Tropical Medicine, 3rd ed., 1919, 924; Mychota Enderlein, Bakterien- 

 Cyclogenie, 1924, 236; Schizotnyceiae Stanier and van Niel, Jour. Bact., 4^, 1941, 458). 



Schi.zo.m\-.ce'tes. Or. noun schiza cleft, fission; Gr. noun myces, mycetis fungus; 

 M.L. mas. pi. n. Schizomycetes the class of fission fungi. 



Tj'pically unicellular plants. Cells usually small, sometimes ultramicroscopic. Fre- 

 quently motile. For many years it was thought that the cells of Schizomycetes and of the re- 

 lated Schizophyceae did not possess the nucleus invariably found in the cells of other plants. 

 However, using modern cytological techniques, investigators have now demonstrated a 

 true nucleus in bacterial cells. Individual cells maj- be spherical or straight, curved or spiral 

 rods. These cells may occur in regular or irregular masses, or even in cysts. Where they re- 

 main attached to each other after cell division, they may form chains or even definite 

 trichomes. The latter may show some differentiation into holdfast cells and into motile 

 or non-motile reproductive cells. Some grow as branching mycelial threads whose diameter 

 is not greater than that of ordinary bacterial cells, i.e., about one micron. Some species 

 produce pigments. The true purple and green bacteria possess pigments much like or related 

 to the true chlorophylls of higher plants. These pigments have photosynt^etic properties. 

 The phycocyanin found in the blue-green algae does not occur in the Schizomycetes . Multi- 

 plication is typically by cell division. Endospores are formed by some species included in 

 Eubacteriales. Sporocj'sts are found in Myxobacterales. Ultramicroscopic reproductive 

 bodies are found in Myco-plasmaiales . The bacteria are free-living, saprophytic, parasitic or 

 even pathogenic. The latter t3-pes cause diseases of either plants or animals. Ten orders 

 are recognized. 



Key to the orders of class Schizomycetes. 



I. Cells rigid. Spherical, rod-shaped (straight or curved) or spiral in form. Sometimes in 

 trichomes. Motile by means of polar flagella or non-motile. 



A. Cells coccoid, straight or curved rods, or spiral in foi-m. Sometimes occur as chains 

 of cells. Cells may contain photosynthetic purple or green pigments. Not in tri- 

 chromes. Usually motile by means of polar fiagella. Occasionally non-motile. 



Order I. Pseudomonadales, p. 35. 



B. Not as above. 



1. Cells in trichomes that are frequentl}' in a sheath. Occasionally motile (swarm 

 spores) or non-motile conidia are developed. The sheaths may contain a deposit 

 of ferric hydroxide, and the trichomes may be attached to a substrate. 



Order II. Chlamydohacteriales , p. 262. 



2. Cells reproduce by a process of budding rather than by ordinary cell division (fis- 

 sion). May be attached to a substrate by a stalk. One genus contains species with 

 photosynthetic pigments {Rhodomicrobium) . 



Order III. Hyphomicrobiales , p. 276. 

 II. Not as above. 



A. Cells rigid. Spherical or straight rod-shaped cells. Occur singly, in chains or in tri- 

 chomes. Motile by means of peritrichous flagella or non-motile. Not acid-fast. 

 1. Cells spherical or rod-shaped; no trichomes though chains of cells may occur. 



Order IV. Eubacteriales, p. 281. 



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