146 



OUTLINES OF BACTERIOLOGY 



The genus includes the following species : 



BEGGIATOA ALBA. Threads, 2-8-2-9 p thick. Length of individual 

 cells, 2-9-5-8^. 



BEGGIATOA MEDIA. Threads, 1 -6-1 -7 p thick. Length of indi- 

 vidual cells, 4-8-5 //. 



FIG. 82. Beggiatoa alba, (a) In medium containing a plentiful supply of 

 sulphuretted hydrogen. (6) In medium devoid of sulphuretted hydrogen : 

 appearance after twenty-four hours ; sulphur granules rapidly disappearing, 

 (c) Appearance three days after deprivation of sulphuretted hydrogen ; sulphur 

 has completely disappeared and transverse walls have been formed, (d) Filament 

 breaking up into fragments. (After Winogradsky.) 



BEGGIATOA MINIMUM. Threads, 0-8 p. thick. 



BEGGIATOA MIRABILIS (Fig. 83). Cylindrical, very actively motile 

 threads. As the thickness of the thread measures up to 45 /*, 

 the individual cells can be seen with the aid of a small magni- 

 fication. The length of the cells is about half the thickness 

 of the thread. 



FIG. 83. Beggiatoa mirabilis. (a) Vacuoles. (6) Sulphur globules. (After Hinze.) 



This gigantic organism has a sharply contoured wall, and the cell 

 contents show a number of vacuoles in the protoplasm, just as we see 

 in mature cells of higher plants. These vacuoles are filled with cell- 

 sap. 



II. Thiothrix. This genus is distinguished from the preceding by 

 its immobility. One end is always attached by a mucilaginous cushion 

 secreted by itself, to any convenient object, a stone for example, the 



