i8o SULPHUR BACTERIA 



is stained by aceto-carmine. Compare with sulphur globules 

 of Thiophysa volutans. This reagent dissolves the sulphur 

 and stains the core after twenty-four hours. The core can 

 also be stained with carbol fuchsin and other reagents. It 

 is probably a nitrogenous reserve material of the organism. 

 The sulphur may be dissolved by chloroform, hot potassium 

 nitrate, or 50 per cent, acetic acid ; in the last named an ex- 

 posure of twenty-four hours is necessary. In strong picric 

 acid solution the globules tend to fuse to form larger irregular 

 drops, but complete solution does not take place. They are 

 unaffected by strong hydrochloric acid, and are insoluble in 

 water. When dissolved, and free from the cell, they frequently 

 combine to form typical sulphur crystals (Fig. 34^). 



Thiophysa volutans (Hinze). 



This is a colourless, motile organism, spherical in shape, 

 which was found in the Gulf of Naples, near a submarine 

 sulphur spring. The cocci measure 7— 18/i. in diameter 



(Fig. 17)- 



The membrane is double contoured and o-jjx thick. It 

 gives the reaction for pectin. Three distinct layers can be 

 distinguished with Delafield's hgematoxylin. 



The protoplast consists of a very delicate hyaline layer on 

 the inner side of the membrane, and from it radiate fine threads 

 of plasma, the whole forming a delicate network. The central 

 portion is occupied by a large vacuole. The cytoplasm can 

 be separated from the membrane by plasmolysis. 



The sulphur globules are insoluble in mineral acids and 

 alkalis, they are partly soluble in acetic acid, and very soluble 

 in alcohol and chloroform. In concentrated glycerine they 

 crystallize out, and form monoclinic crystals outside the cell, 

 several droplets uniting to form one crystal (Fig. lyd). 



Sulphur Builders. — These are bodies ranging from 4/x to a 

 size when they are scarcely visible. They are ovoid or round, 

 are of a dull green colour, and occupy the vacuoles in great num- 

 bers. They stain with methylene blue, Congo red, and other 

 reagents ; are insoluble in i per cent, potassium hydrate, 



