ORDER I. PSEUDOMONADALES ORLA -JENSEN, 1921. 



(Jour. Bact., 6, 1921, 270.) 



Pseu.do.mo.na.da'les. M.L. fern. pi. n. Pseudomonadaceae type family of the order; -ales 

 ending to denote an order; M.L. fem.pl.n. Pseudomonadales the Pseudomonadaceae order. 



Straight, curved or spiral, rigid, rod -shaped bacteria. Rarely occur in pairs or chains. 

 The cells in a few species are ellipsoidal and are frequently spoken of as being coccoid or 

 even spherical in form. They are usually about 1.0 micron in diameter, but in a few species 

 the individual cell is larger than is normal for bacterial cells, reaching a size of 3.0 to 14.0 

 microns in diameter and as much as 100 microns in length. The cells are usually polar flagel- 

 late. When motile they sometimes bear a single flagellum, in other cases a tuft of flagella. 

 The flagella are normally found at one or both ends of the cell, but in one genus the curved 

 cells bear a tuft of flagella that is attached in the middle of the concave side (Selenomonas) . 

 Non-motile species whose characteristics indicate that thej' belong in this order with closely 

 related, motile species occasionally occur. Cells are Gram-negative so far as known. The 

 cells in one sub-order contain pigments that have the power of photosynthesis. The cells 

 in the second sub-order lack such pigments, as do all other groups of bacteria. The cells 

 in the first sub-order are photo-autotrophic, while chemo-autotrophic species occur in the 

 second sub-order. Energy is frequently secured by oxidative processes though there are also 

 many species that show a fermentative physiology. Cells quite frequently occur in zoogloeal 

 masses. No endospores are found, and reproduction is by means of fission. Many species 

 occur in coastal, swamp and pond waters and in soil. Some are parasitic and some are even 

 pathogenic, causing diseases of fishes and other cold-blooded vertebrates. There are a few 

 species (cholera, blue pus, etc.) that cause diseases of warm-blooded mammals, including 

 man. 



Kerj to the sub -orders of order Pseudomonadales. 



I. Cells contain red, purple, brown or green photosynthetic pigments. Sometimes also 

 enclose granules of free sulfur. 



Sub-order I. Rhodobacteriineae , p. 35. 

 II. Cells do not contain photosynthetic pigments, although they may produce greenish, 

 brownish, rose or yellow, diffusible, water-soluble pigments or yellow or red non-water- 

 soluble pigments. Free sulfur granules may occur within or without the cells (Thio- 

 bacteriaceae). Ferric hydroxide may be deposited (Caulobacteriaceae) . 



Sub -order II. Pseudomonadineae, p. 67. 



Suborder I. Rhodobacteriineae Breed, Murray and Kitchens, 1944.* 



(Family Rhodobacteriaceae Migula, Syst. d. Bakt., 2, 1900, 1042; Breed, Murray and 

 Hitchens, Bact. Rev., 8, 1944, 257.) 



Rho.do.bac.te.ri.i'ne.ae. M.L. neut.n. Rhodobacteriuin a genus of bacteria; -ineue end- 

 ing to denote a suborder; M.L. fem.pl.n. Rhodobacteriineae the Rhodobacterium suborder. 



* Rearranged and revised by Prof. C. B. van Niel, Hopkins Marine Station, Pacific 

 Grove, California, July, 1953. 



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