238 SULPHUR BACTERIA 



the ether with a yellow colour. Hence the alcohol extract 

 contains a component which is more soluble in petroleum 

 ether than in alcohol. The following experiment shows that 

 the bacteriopurpurin obtained by Molisch from the non- 

 sulphur purple bacteria is identical with the purple colouring 

 matter of the sulphur bacteria. 



When the purple chloroform extract of Thioporphyra 

 volutans was filtered and evaporated, coloured crystals and an 

 oily substance separated out. The crystals were then ex- 

 tracted with cold water, filtered and again evaporated. The 

 residue was a thin brown skin which formed an intense reddish- 

 brown solution with carbon bisulphide. The crystals were 

 similar to those obtained by Molisch. The experiment also 

 showed that in the plant the purple colouring matter is in all 

 probability dissolved in the oil, from which it cannot be 

 extracted by water, but that with the removal of the oil they 

 can be taken up by water. 



The spectroscopic examination of coloured extracts from 

 material growing on seaweed was unsatisfactory, for the 

 disintegrated Fucus cells were a source of chlorophylls and 

 carotinoid pigments. The spectrum of the purple fluid 

 exhibited the characteristic bands of chlorophyll ; and this 

 occurred even when, owing to careful scraping, at least 90 per 

 cent, of the colour was derived from the microbe. 



The organisms were then grown on cardboard in culture 

 pools and the coloured material was collected from the deposit 

 which formed thereon. The absorption spectrum showed a 

 complete absence of absorption bands and localized darkened 

 areas, and the same results were obtained with both the purple 

 and the brown-green fluids. The complete absence of chloro- 

 phyll was shown by the absence of the very distinctive dark 

 band in the red between B and C (see Fig. 65, V). There was a 

 certain amount of end-absorption, particularly on the violet 

 side, when the purple fluids were used, and the extent of the 

 end-absorption was dependent on the thickness of the fluid. 



This unexpected result appears to place the colouring 

 matter of Thioporphyra volutans in a different category from 

 those of the other sulpliur bacteria, but it is considered that in 



