FAMILY I. BEGGIATOACEAE 



843 



B. Diameter of trichomes is less than 0.5 micron. 



3. Thiothrix tenuissima. 

 II. From marine environments. 



A. Diameter of trichomes is greater than 15 microns. 



4. Thiothrix voukii. 



B. Diameter of trichomes is less than 15 microns. 



1. Diameter of trichomes is greater than 1.8 microns. 



a. Segments about 25 microns long. 



5. Thiothrix longiarticulata. 

 aa. Segments about 1 micron long. 



6. Thiothrix anulata. 



2. Diameter of trichomes is less than 1.8 microns. 



7. Thiothrix marina. 



1. Thiothrix nivea (Rabenhorst, 1865) 

 Winogradsky, 1888. {Beggiatoa nivea Raben- 

 horst, Flora europaea algarum, 2, 1865, 94; 

 Winogradsky, Beitr. z. Morph. u. Physiol, 

 d. Bact., I, Schwefelbacterien, 1888, 39.) 



ni've.a. L. adj. niveus snow-white. 



Trichomes, 2.0 to 3.0 microns at the base, 

 1.7 microns in the middle and 1.4 to 1.5 mi- 

 crons at the tip, occurring within a thin 

 sheath. Segmentation invisible as long as 

 the trichomes contain sulfur globules; the 

 segments measure 4 to 15 microns, the longer 

 ones usually near the apex, the shorter ones 

 near the base. Motile segments (so-called 

 conidia) are mostly single, 8 to 15 microns 

 long, sometimes occurring in short tri- 

 chomes of 2 to 4 cells and measuring up to 

 40 microns long. These segments may settle 

 and develop near the base of the parent 

 trichome or on a trichome itself, forming 

 verticillate structures. 



Habitat: Found in fresh-water environ- 

 ments where hydrogen sulfide is present 

 (sulfur springs, stagnant pools, submerged 

 decaying vegetation, etc.). 



2. Thiothrix tenuis Winogradsky, 1888. 

 {Beggiatoa alba var. uniserialis Engler, tJber 

 die Pilz-Vegetation des weissen oder todten 

 Grundes in der Kieler Bucht. Vierter Be- 

 richt der Commission zur wissenschaft- 

 lichen Untersuchung der deutschen Meere 

 in Kiel fiir 1877 bis 1881, Abt. I, 1883, 187- 

 193; Winogradsky, Beitr. z. Morph. u. Phys- 

 iol, d. Bact., I, Schwefelbacterien, 1888, 

 40.) 



te'nu.is. L. adj. tenuis slender. 



Trichomes, about 1 micron in diameter, 

 of nearly uniform width, often occurring in 



dense, felted masses. Segments 4 to 5 mi- 

 crons long. 



Habitat: Found in fresh-water environ- 

 ments where hydrogen sulfide occurs. Also 

 found in sea water, according to Baven- 

 damm (Die farblosen und roten Schwefel- 

 bacterien, Pflanzenforschung, Heft 2, 1924, 

 107). 



3. Thiothrix tenuissima Winogradsky, 

 1888. (Beitr. z. Morph. u. Physiol, d. Bact., 

 I, Schwefelbacterien, 1888, 40.) 



te.nu.is'si.ma. L. sup. adj. tenuissimus 

 very slender. 



Trichomes less than 0.5 micron in diame- 

 ter, usually occurring in dense masses. 



Habitat: Found in fresh-water environ- 

 ments where hydrogen sulfide occurs. 



4. Thiothrix voukii Klas, 1936. (Arch. f. 

 Protistenk., 88, 1936, 123.) 



vou'ki.i. M.L. gen. noun voukii of Vouk; 

 named for Vouk, a Yugoslavian scientist. 



Trichomes, 15 to 30, most frequently 17, 

 microns in diameter, of rather uniform 

 width. Segments visible without special 

 treatment. Segments generally somewhat 

 longer than wide, occasionally barrel- 

 shaped, rarely square. Segments 15 to 30, 

 mostly 19 to 23, microns in length. Motile 

 segments not yet observed. 



Comment : Apart from the lack of motil- 

 ity, this species closely resembles the motile 

 Beggiatoa mirabilis. 



Source: Described from the effluent of 

 sulfur springs at the seashore near Split, 

 Yugoslavia. So far reported only once. 



Habitat: Found in marine environments 

 containing hydrogen sulfide. 



