Page:Bergey's manual of determinative bacteriology.djvu/55

 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, 1, Heft 2, 1872, 127; Bacteriaceae Cohn, Arch. f. path. Anat., 55, 1872, 237; Schizomycetaceae 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 Chalmers, Manual of Tropical Medicine, 3rd ed., 1919, 924; Mychota Enderlein, Bakterien-Cyclogenie, 1924, 236; Schizomycetae Stanier and van Niel, Jour. Bact., 42, 1941, 458).

Schi.zo.my.ce′tes. Gr. noun schiza cleft, fission; Gr. noun myces, mycetis fungus; M.L. mas. pl. n. Schizomycetes the class of fission fungi.

Typically unicellular plants. Cells usually small, sometimes ultramicroscopic. Frequently motile. For many years it was thought that the cells of Schizomycetes and of the related 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 may be spherical or straight, curved or spiral rods. These cells may occur in regular or irregular masses, or even in cysts. Where they remain 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 photosynthetic properties. The phycocyanin found in the blue-green algae does not occur in the Schizomycetes. Multiplication is typically by cell division. Endospores are formed by some species included in Eubacteriales. Sporocysts are found in Myxobacterales. Ultramicroscopic reproductive bodies are found in Mycoplasmatales. The bacteria are free-living, saprophytic, parasitic or even pathogenic. The latter types cause diseases of either plants or animals. Ten orders are recognized.


 * 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 form. Sometimes occur as chains of cells. Cells may contain photosynthetic purple or green pigments. Not in trichromes. Usually motile by means of polar flagella. Occasionally non-motile.


 * B. Not as above.


 * 1. Cells in trichomes that are frequently 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.


 * 2. Cells reproduce by a process of budding rather than by ordinary cell division (fission). May be attached to a substrate by a stalk. One genus contains species with photosynthetic pigments (Rhodomicrobium).


 * II. Not as above.


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