996 MANUAL OF DETERMINATIVE BACTERIOLOGY 



have been made. Since (a) the internal locality from which Thiosiphon was col- 

 structure of the large Beggiatoaceae is lected is almost certain, and (d) the dc- 

 easily damaged, (b) the segmentation in velopmental cycle is merely a reconstruc 

 living individuals is difficult to observe tion of simultaneously observed ele- 

 when the filaments are filled with sulfur, ments, considerable doubt as to the 

 (c) the presence of Achromalium in the validity of the genus appears justified. 



* Appendix I: The group of large, unicellular, colorless sulfur bacteria is placed here 

 as a single family, Achromatiaceae Massart as in previous editions of the ISIanual. 

 It includes organisms which are similar in physiology to the Beggiatoaceae. 



Massart (Rec. Inst. Bot. Univ. Bruxelles, 5, 1902, 251) proposed the family Achro- 

 matiaceae for the bacteria described by Schewiakoff (tjber einen neuen bacterienahn- 

 lichen Organ ismus des Siisswassers, Habilitationsschrift, Heidelberg, 1893) as Achro- 

 matitim oxaliferum. The family diagnosis was modified by Nadson (.Jour. Microbiol., 

 St. Petersb., 1, 1914, 72) and by Nadson and Wislouch (Bull. Princip. Jard. Bot. 

 R^publ. Russe, 22, 1923, 33) to include the genera Thiophysa and Thiosphaerella. 



In this form, the family represents a homogeneous group of organisms, all char- 

 acterized by a pronounced similarity in cell-shape, structure, method of reproduction 

 and motility. They exhibit very slow, jerky and rotating movements, but' are de- 

 void of flagella or other visible organs of locomotion. They closely resemble the 

 blue-green algae of the genus Synechococcus, even in size. 



By including the genus Thiospira in the family Achromatiaceae, Buchanan (Jour. 

 Bact., 3, 1918, 462) modified the diagnosis to read: 



Unicellular, large, motile (by means of flagella?). Cells containing granules of sulfur (or in one form 

 possibly oxalate) but no bacteriopurpurin. 



Thus was proposed a family in which the spiral sulfur bacteria, indubitably related 

 to species of Spirillum among the Eubacteriales , were linked with the taxonomieally 

 obscure species included in Achromalium and Thiophysa. Four genera, Achroma- 

 lium, Thiophysa, Thiospira and Hillhousia were recognized. 



Bavendamm (Die farblosen und roten Schwefelbakterien, Pflanzenforschung, 

 Heft 2, 1924, 109), following the same trend, also combined all non-filamentous forms 

 of the colorless sulfur bacteria into a family Achromatiaceae, with the diagnosis: 

 Cells free, motile. As he realized that Hillhousia should be regarded as a synonym 

 of Achromalium and added the genus Thiovulum Hinze (Ber. d. deut. bot. Ges., 31, 

 1913, 195), four genera were again included in the family. Thiosphaerella was added 

 as an appendix to Thiophysa. 



Thiovulum is morphologically similar to Achromalium, Thiophysa, and Thio- 

 sphaerella with respect to cell size and structure, but differs conspicuously in being 

 actively and rapidly motile. The manner of locomotion suggests the presence of 

 polarly inserted flagella. However, these hnve never been demonstrated con- 

 vincingly. 



While it is conceivable that a relationship exists between Thiovulum and the or- 

 ganisms of the Achromaliimi type, the combination of the representatives into one 

 family should be regarded as tentative and open to question. There certainly is no 

 justification at present for including the sulfur spirilla in this family. These are 

 placed in this edition of the Manual in Spirilleae among the Eubacteriales. 



* Completely revised by Prof. C. B. Van Niel, Hopkins Marine Station, Pacific 

 Grove, California, January, 1944. 



