988 MANUAL OF DETERMINATIVE BACTERIOLOGY 



FAMILY III. BEGGIATOACEAE MIGULA.* 



(Arb. Bakt. Inst. Karlsruhe, 1, 1894, 238: in part, Lcuco-Thiobacteria Bavendamm, 

 Die farblosen and roten Schwefelbakterien, Pflanzenforschuug, Heft 2, 1924, 102.) 



Filamentous organisms, composed of chains of cells. Individual cells generally 

 not visible without staining. Structure very similar to that of Oscillatwiaceae, but 

 devoid of chlorophyll and phycocyanin. When growing in the presence of hydrogen 

 sulfide, the filaments contain sulfur globules. Special reproductive structures 

 unknown . 



In proposing the family Beggiatoaceae for the two genera of this subgroup known 

 in 1894, Migula remarked that "it would be best to combine them with the Oscilla- 

 toriaceae and classify them among the Schizophyta" (Arb. Bakt. Inst. Karlsruhe, 1, 

 1894, 238). The same authority has stated : "Also in view of their internal structure 

 the species of Beggiatoa are so similar to those in the genus Oscillaria that they can 

 hardly be separated generically" (in Engler and Prantl, Die natiirl. Pflanzenfam., 

 ;, la, 1895,41). 



Since then, the close relationship between the filamentous, colorless sulfur bacteria 

 and the blue-green algae of the family Oscillatoriaceae has become increasingly clear. 

 A particularly important line of evidence is supplied by the discovery of sulfur bac- 

 teria paralleling each of the major genera of the Oscillatoriaceae . The family Beggia- 

 toaceae Migula is retained for these filamentous sulfur bacteria. Taxonomically 

 they could readily be classified as colorless members of the class Schizophyceae . 



Key to the genera of family Beggiatoaceae. 



I. Filaments non -motile. Grow attached by means of holdfast at base. 



Genus I. Thiothrix, p. 988. 

 II. Filaments motile, like Oscillatoria, by creeping or sliding movements along a 

 solid substrate. Not attached. 



A. Occurring singly, not embedded in a common slime-sheath. 



1. Filaments straight or bent, but not permanently coiled. 



Genus II. Beggiatoa, p. 990. 



2. Filaments coiled or spirally wound. 



Genus III. Tfnuspirillopsis, p. 993. 



B. Occurring in bundles, embedded in a common slime-sheath. 



Genus IV. Thioploca, p. 993. 



Genus I. Thiothrix Winogradsky. 



(Beitr. z. Morph. u. Physiol, d. Bakt., I, Schwefelbacterien, Leipsig, 1888, 

 39.) From Greek theion, sulfur, and thrix, hair. 



Filaments non-motile, segmented, with a delicate sheath, and differentiated into 

 base and tip. Grow attached at base to solid objects by means of gelatinous hold- 

 fast. Reproduction by transverse fission of the segments, and by rod-shaped so- 

 called conidia, probably arising by the apical segments becoming free . Temporarily, 

 the conidia show creeping motility, settle on solid objects, and grow out into new 

 filaments. 



The type species is Thiothrix nivea (Rabenhorst) Winogradsky. 



The following key to the species of the genus Thiothrix is based upon the diameter 



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

 Grove, California, January, 1944. 



