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ORDER I. PSEUDOMONADALES 



1. Chlorochromatium aggregatum 



Lauterborn, 1906. (AUgem. botan. Ztschr., 

 19, 1906, 196.) 



ag.gre.ga'tum. L. part. adj. aggregatus 

 flocked together, clumped. 



Cells of the green component 0.5 to 1.0 by 

 1.0 to 2.5 microns, mostly from 8 to 16 in- 

 dividuals surrounding the central bac- 

 terium. Size of the total barrel-shaped unit 

 variable, generally 2.5 to 5 by 7 to 12 mi- 

 crons. Occasionally a group of the complex 

 colonies may remain attached in a chain. 



Anaerobic. 



Habitat: Mud and stagnant water con- 

 taining rather high concentrations of hydro- 

 gen sulfide and exposed to light. 



There is at present no good reason for 

 distinguishing 2 varieties (forma typica and 

 forma minor) or even species, on the basis 

 of size differences of the colony, as Geitler 

 proposed (Die Siisswasserflora Deutsch- 

 lands, Osterreichs und der Schweiz, Jena, 

 12, 1925, 460). The reported and personally 

 observed sizes of such units show that the 

 extreme limits are linked by a complete 

 series of transitions. 



Illustrations: Buder, Ber. deut. botan. 

 Ges., 31, 1914, Generalversam., PI. XXIV, 

 fig. 1-5; Perfiliev, Jour. Microbiol. (Rus- 

 sian), 1, 1914, fig. 1-5, p. 213. 



Genus VI. Cylindrogloea Perfiliev, 1914- 

 (Jour. Microbiol. (Russian), 1, 1914, 223.) 



Cy.lin.dro.gloe'a. Gr. noun cylindrus cylinder; Gr. novm gloea gum; M.L. fem.n. Cylin- 

 drogloea cylindrical gum. 



Sulfur green bacteria consisting of small ovoid to rod-shaped cells growing in association 

 with a filamentous, colorless, central bacterium, thus forming colonies of a cylindrical 

 shape. Non-motile. The green component contains a chlorophyllous pigment different from 

 the common chlorophylls of green plants and from bacteriochlorophyll. Capable of photo- 

 synthesis in the presence of hydrogen sulfide without depositing sulfur globules in the cells. 



The type species is Cylindrogloea bacterifera Perfiliev. 



1. Cylindrogloea bacterifera Perfiliev, 

 1914. (Jour. Microbiol. (Russian), 1, 1914, 

 223.) 



bac.te.ri'fe.ra. Gr. neut.n. bactrum a rod; 

 M.L. mas.n. bacter rod (a combining form); 

 L. verbal suf. fer bearing; M.L. adj. bac- 

 terifera rod-bearing. 



Individual green components ovoid to 

 rod-shaped, about 0.5 to 1 by 2 to 4 microns, 

 very similar to those of the complex Chloro- 

 bacterium symbioiicum and Chlorochromatium 

 aggregatum with which they may well be 

 identical. The central filamentous bac- 

 terium is embedded in a slime capsule of 

 considerable dimensions. This, in turn, is 

 surrounded by a layer of green bacteria, 

 usually one cell thick. The green organisms 

 may form a very dense outer covering, or 

 they may be more sparsely distributed over 

 the slime capsule. The entire unit is again 

 surrounded by a sizeable slime zone. Aggre- 

 gates measure about 7 to 8 microns in width 

 and up to 50 microns in length; they are non- 



motile. Both components appear to be 

 non -spore-forming. 



Habitat: Mud and stagnant water con- 

 taining rather high concentrations of hj^dro- 

 gen sulfide and exposed to light. 



Illustration: Perfiliev, ibid., fig. 6-11, p. 

 213. 



Perfiliev rightly emphasizes, as Buder had 

 done for Chloronium mirabile, the provi- 

 sional nature of thus using a generic desig- 

 nation for an apparently stable complex 

 composed of two different organisms. It re- 

 mains possible that the last three genera of 

 symbiotic entities represent fortuitous com- 

 binations whose occurrence is conditioned 

 by environmental factors. If so, the generic 

 terminology would be devoid of any taxo- 

 nomic significance, and the green bacteria 

 should be relegated to more appropriate 

 genera. Indications suggestive of this state 

 of affairs can be found in the literature ; for 

 example in Utermohl's observation (Archiv 



