FAMILY ATHIORHODACEAE 



863 



1. Rhodopseudomonas palustris (^lo- 

 lisch) van Xiel. {Rhodobacilliis palustris 

 Molisch, Rhodobacteriuni capsulatum Mo- 

 lisch and Rhodovibrio pannis Molisch, 

 Die Purpurbakterien, Jena, 1907, 14, 18 

 and 21; Rhodonionas palustris Kluyver 

 and van Niel, Cent. f. Bakt., II Abt., 94, 

 1936, 397; Rhodopseudomonas No. 9 and 

 Xo. 16, Czurda and ^laresch. Arch. f. 

 Mikrobiol., 8, 1937, 120; van Kiel, Bact. 

 Rev., 8, 1944, 89.) From Latin paluster, 

 boggy, marshy. 



Cells: Usually distinctly rod-shaped, 

 > though in young cultures very short, 

 lightly curved rods may often pre- 

 dominate. Size variable, even for the 

 same strain, and strongly influenced by 

 age of culture and composition of me- 

 dium. Rather consistently short cells 

 in young cultures in yeast extract, espe- 

 cially when incubated anaerobically in 

 the light, or in anaerobic cultures with 

 substrates which permit only a slow" and 

 scanty development, such as malonate. 

 Dimensions in such cultures 0.6 to 0.8 bj- 

 1.2 to 2 microns. ^lore often, especially 

 in older cultures, cells are much longer, 

 up to 10 microns. Highly characteristic 

 is the pronounced tendency to the forma- 

 tion of irregularly shaped, bent and 

 crooked long rods, occasionally swollen 

 at one or both extremities, and fre- 

 quently suggesting branching. Such 

 cells usually form clusters reminiscent 

 of Corynebactcrium and Mycobacteriutn 

 cultures. 



Cells in young cultures actively motile 

 by means of polar flagella; irregular and 

 long cells as a rule non-motile. Gram- 

 negative. 



Growth in liquid media never mucoid; 

 sediment in older cultures homogeneous 

 and smooth, readily redispersible. 



Color: Varies considerably, depending 

 upon the medium, and especially in 

 anaerobic illuminated cultures. Where 

 development is slight (as in malonate, 

 thiosulfate, and, usually, glycerol me- 

 dia), the color is a light pink; in fatty 

 acid-containing media more nearly dark 

 reddish-brown. Color due to bacterio- 



chlorophyll and a number of different 

 carotenoid pigments; most strains pro- 

 duce in addition a water-soluble, non- 

 carotenoid, bluish-red pigment which 

 diffuses into the culture medium. 



In yeast extract cultures growth is 

 possible over the range pH 6 to 8.5. 

 With certain substrates, especially fatty 

 acids, the combined effect of low pH and 

 a substrate concentration of 0.1 to 0.2 

 per cent may prevent growth. No char- 

 acteristic odors save that old cultures 

 may develop a distinct ionone-likp frag- 

 rance. Gelatin is not liquefied; leucine 

 is generally utilized as a substrate. 



Most strains are able to grow on the 

 surface of agar plates or slants; a few, 

 especially when first isolated, appear 

 more sensitive to oxygen and develop 

 only in stabs in which the upper region 

 may remain free of growth. Generally 

 such strains can be adapted to grow at 

 full atmospheric oxygen tension. 



Most fatty acids and hydroxj' acids 

 are adequate oxidation substrates. All 

 cultures can grow at the expense of thio- 

 sulfate and produce rapid and profuse 

 growth in glutarate and ethanol media. 

 No development in media containing as 

 the chief oxidation substrate 0.2 per cent 

 sorbitol, glucose or mannose, even 

 though these substances are not inhibi- 

 tor^^ Molecular hj^drogen can be oxi- 

 dized. 



All cultures can develop anaerobically 

 in illuminated cultures bj^ photo- 

 synthesis. 



Temperature optimum generally 

 rather high, good development being 

 possible up to 37 °C. However, certain 

 strains exhibit a lower temperature 

 optimum . 



Distinguishing characteristics: Mor- 

 phological resemblance to species of 

 Mycobacterium in old cultures; ability 

 to grow with thiosulfate as the chief 

 oxidizable substrate, and failure to 

 develop in media which contain carbo- 

 hydrates or sugar alcohols in a concen- 

 tration of 0.2 per cent as the main oxidiz- 

 able compounds. 



