INTERNATIONAL JOURNAL of SYSTEMATIC BACTERIOLOGY Vol. 21, No. 1 January 1971, p. 8-10. Printed in U.S.A. Copyright 0 1971 lnternational Journal of Microbiological Societies Family of Phototrophic Green : Chloro biaceae Copeland, the Correct Family Name; Rejection of Chlorobacteriurn Lauterborn; -and the Taxonomic Situation of the Consortium-FormingSpecies Request for an Opinion

HANS G. TRUPER and NORBERT PFENNIG

Institut fur Mikrobiologie der GSF, 34 Gzttingen, Germany

The family of phototrophic contains five genera: Chlorobium Nadson 1906, Pelodictyon Lauterborn 19 13, ClathrochZoris Geitler 1925, Chloropseudomonas Czurda and Maresch 1937, and Prosthe- cochloris Gorlenko 1970. Of these, Chlorobium is the type , and the name of the family is Chlorobiaceae Copeland 1956. The familial name Chlorobacteriaceae Lauterborn 19 13 is illegitimate. Furthermore, the applications of the names Chlorobacterium Lauterborn 19 16 and C. symbioticum Lauterborn 1916 are uncertain, and the Judicial Commission is requested to place these names in the list of rejected names. The taxonomic situation of the consortium-forming “symbiotic ” of the phototrophic green sulfur bacteria (ChZorochroma tium aggregatum, Chlorochromatium glebulum, Pelochromatium roseum, and Cylindrogloea bacterifera) is discussed.

The phototrophic green sulfur bacteria pres- Furthermore, there is some question con- ently (Bergey’s Manual of Determinative Bac- cerning the legitimacy of the generic name teriology, 7th ed.) are placed in the family Chlorobacterium Lauterborn itself. It appears Chlorobacteriaceae Lauterborn 19 13. However, from Lauterborn’s description that the only this family name is illegitimate because, when species of this genus, C. symbioticum, is an originally proposed, it was not based on one of obligately symbiotic microorganism living as an the contained genera, which were Chlorochro- outer cover of certain protozoa such as matium, Pelodictyon, Schmidlea, Pelogloea, amoebae and flagellates. Lauterborn classified and Pelochromatiurn. Subsequent to the publi- this green organism as a phototrophic sulfur cation of the familial name Chlorobacteriaceae, bacterium, although neither the presence of Lauterborn (9) published the generic name in the original habitats nor the Chlorobacterium. However, this does not ren- oxidation of hydrogen sulfide by the cells to der the name Chlorobacteriaceae legitimate. extracellularly deposited elemental sulfur was Chlorobacterium Lauterborn 19 16 is ordi- mentioned. Furthermore, no evidence was given narily cited as the type genus of the family to show the presence of or Chlorobacteriaceae Lauterborn 19 13. However, other photosynthetic pigments. The light de- this is not possible, for by definition the type pendance of growth was also not shown. of a family is the genus on whose name the Finally, there was not even proof presented to family is based. Obviously the name Chloro- show that this green microorganism is a bac- bacteriaceae could not have been based on the terium. Significantly enough, van Niel, in genus ChEorobacterium, because the genus was Bergey’s Manual (18), put a question mark not described until 3 years after the family behind the word “bacteria” in the description name had been given! It appears that the of this organism. The reason for the very generic name was derived from the familial limited knowledge about this organism is that, name instead of vice versa. since Lauterborn’s original description, no 8 VOL. 21, 1971 CHLOROBIA CEAE COPE LAND 9 other observations of the organism have been chlorochromatii. His isolate was lost before reported. It is quite clear, then, that the extensive comparative studies with other applications of the names Chlorobacterium and Chlorobium species could be done. The culture C. symbioticurn Lauterborn are uncertain. The conditions used by Mechsner did not allow Judicial Commission is therefore requested to growth of the entire consortium. More recently, place these nomina dubia on the list of rejected the enrichment culture of the consortium has names. been reported (13). At present, there is little At present, the phototrophic green sulfur doubt that the green component is indeed a bacteria are placed in five genera: Chlorobium member of the genus Chlorobium. Nadson 1906, Pelodictyon Lauterborn 19 13, Consortium “Chlorochromatium glebulum” Clathrochloris Geitler 1925, Chloropseudo- Skuja 1956. This aggregate is similar to the nzonas Czurda and Maresch 1937 (15), and “Chloro ch roma tium aggrega tum ” consortium, Prosthecochloris Gorlenko 1970. Of these, only but the cells of the green component contain Chlorobium has had a family name based on it. gas vacuoles, and Skuja (1 6) states morpholog- Thus, Chlorobiacea (sic) Copeland 1956 (here ical similarity of the green component with corrected to Chlorobiaceae) is the correct name Pelodictyon luteolum (synonym P. aggregatum). of the family of phototrophic green sulfur Since the consortium has never been grown in bacteria containing the five genera cited above. enrichment or pure culture, there is no experi- That Chlorobium is the type genus of this mental evidence that the green component family is especially fortuitous, because this belongs to the Chlorobiaceae. genus contains the most widespread and best known species (free living and all studied in Consortium “Pelochromatium roseum” pure culture) of the phototrophic green sulfur Lauterborn 1913. The aggregate is similar to bacteria. the “Chlorochromatium aggregatum ” con- Besides Chlorobacterium Lauterborn, four sortium, except that the outer cells are not other symbiotic forms of phototrophic sulfur green but pinkish brown in color. This color is bacteria have been described (none was ever very similar to that of pure cultures of two grown in pure culture). All of these, however, newly described pinkish brown Chlorobium were named as consortia. By “consortium” is species (1 4). The similarity is substantiated by meant an aggregate or association of two the identity of the in vivo absorption spectra different organisms. Species names were applied (bacteriochlorophyll d and carotenoids of to the consortium rather than to one of the two group 5) of enrichment cultures of the con- components. Because this nomenclature clearly sortium and of pure cultures of the brown violates Rule 14a (3) of the International Code Chlorobium species. The consortium has been of Nomenclature of Bacteria, the names of enriched by using a sulfide-containing culture these consortia have to be considered as not medium (1 3). All these characteristics leave validly published, i.e., “without standing in little doubt that the brown component of the nomenclature.” The names of the consortia consortium may belong to Chlorobiaceae. may be used as laboratory designations, but Utermohl (1 7), studying natural samples, sug- they are without taxonomic value or impor- gested the name Lauterborniola minima for the tance. brown component, which he thought to belong The present knowledge about the consortia to the Phaeobacteria; he named the central organism Endosoma palleum. The taxonomic is roughly summarized below (see also Bergey ’s significance of Utermohl’s suggestions remains Manual, 7th ed.). Consortium “Chlorochromatium aggre- to be evaluated. gatum” Lauterborn 1906. The consortium con- Consortium “Cylindrogloea bacterifera” sists of a rather large colorless polar flagellate Perfiliev 1914. The consortium was described bacterium as the center which is surrounded by to consist of a central filamentous nonmotile green bacteria, arranged in four to six rows bacterium embedded in a large slime capsule, from two to four cells high. The consortium is which is covered by a layer of green bacteria. motile and multiplies by the more or less The green component is described to contain a simultaneous fission of its components. In vivo chlorophyllous pigment not identical with plant spectra of enrichment cultures show maxima or bacteriochlorophyll a. Skuja typical for chlorobium (bacterio- (1 6) depicted the green component as contain- chlorophylls c or d). This consortium is identi- ing gas vacuoles. It seems likely that this cal with the Chloronium mirabile of Buder (1). consortium is a variety of the Chlorochro- Mechsner (10) described the isolation of the matium consortia. The green component might green component and named it Chlorobium be a Chlorobium or Pelodictyon species. 10 TRUPER AND PFENNIG INT. J. SYST. BACTERIOL.

LITERATURE CITED 11. Nadson, G. A. 1906. The morphology of inferior algae 111. Chlorobium limicola Nads., the green 1. Buder, J. 1914. Chloronium mirabile. Ber. Deut. chlorophyll bearing microbe (Russian). Bull. Bot. 31~80-97. Jard. Bot. St. P6treb. 6:199. 2. Czurda,G~s. V., and E. Maresch. 1937. Beitrag zur 12. Perfiiev, B. V. 1914. On the theory of symbiosis Kenn tnis der Athiorhodobakterien-Gesell- of Chlorochromatium aggregatum Lauterb. schaften. Arch. Mikrobiol. 8:99-124. (Chloronium mirabile Buder) and Cylindrogloea 3. Copeland, H. F. 1956. The classification of lower bacterifera nov. gen., nov. spec. (Russian). J. organisms. Pacific Books, Palo Alto, Calif. Mikrobiol. 1:223. 13. Pfennig, N. 1967. Photosynthetic bacteria. Annu. 4. Geitler, L., and A. Pascher. 1925. Cyanochlori- Rev. Microbiol. 21:285-324. p. 451 -463. In A. dinae-Chlorobacteriaceae, 14. Pfennig, N. 1968. Chlorobium phaeobacteroides Pascher (ed.), Die Susswasserflora Deutschlands, Osterreichs und der Schweiz G. Fischer, Jena. nov. spec. und C. phaeovibriodes nov. spec., zwei neue Arten der grunen Schwefelbakterien. 5. Gorlenko, V. M. 1970. A new phototrophic green sulphur bacterium Prosthecochloris aestuari Arch. Mikrobiol. 63:224-226. nov. gen. nov. spec. Z. Allg. Mikrobiol. 10:147- 15. Pfennig, N., and H. G. Triiper. 1969. Proposal to 149. declare Rhodopseudomonas palustris and Chloropseudomonas ethylica as nomina con- 6. International Code of Nomenclature of Bacteria. servanda. Int. J. Syst. Bacteriol. 19: 153-154. 1966. Int. J. Syst. Bacteriol. 16:459-490. 16. Skuja, H. 1956. Taxonomische und biologische 7. Lauterborn, R. 1906. Zur Kenntnis der sapro- Studien iiber das Phytoplankton schwedischer pelischen Flora. Allg. Bot. Z. 12:196-197. Binnengewasser. Nova Acta Regiae. SOC. Sci. 8. Lauterborn, R. 1913. Zur Kenntnis einiger sapro- Upsal. Ser. IV 16:l-104. pelischer Schizomyceten Allg. Bot. Z. 17. Utermohl, H. 1924. Phaeobakterien (Bakterien 19:97 -1 00. mit braunen Farbstoffen). Biol. Zentralbl. 9. Lauterborn, R. 1916. Die sapropelische Lebewelt. 43:605-610. Ein Beitrag zur Biologie des Faulschlammes 18. van Niel, C. B. 1957. Suborder I. Rhodobac- naturlicher Gewasser. Verh. Natur. Med. Ver. teriineae Breed, Murray and Hitchens, 1944, p. Heidelberg 13:395 -481. 35-36. In R. S. Breed, E. G. D. Murray, and N. 10. Mechsner, K. 1957. Physiologische und morpho- R. Smith (ed.), Bergey’s manual of determina- logische Untersuchungen an Chlorobakterien. tive bacteriology, 7th ed. The Williams & Arch. Mikrobiol. 26:32-51. Wilkins Co., Baltimore.