PHOTOGENIC BACTERIA 2OI 



Isolation. Phosphorescent bacteria can be obtained for 

 experimental work by placing oyster shells or the flesh of 

 herring and haddocks in a solution of two to three per cent 

 sodium chloride at 5 C. to 10 C. for a few days. The solid 

 material and the liquid become bluish green in color and emit 

 a pale light. The bacteria can be isolated according to the 

 ordinary bacteriological methods, but must be grown in media 

 containing an infusion of fish, etc., and two to three per cent 

 of sodium chloride. 



Cultures in gelatin containing the above-mentioned ingre- 

 dients may become so luminous as to be photographed in 

 their own light after long exposure. Cultures have been 

 reported which produce enough light for a person to see the 

 face of a watch in total darkness. 



Of the several varieties of photogenic bacteria, Pseudo- 

 monas phosphorescens var. liquef aciens is one of the most com- 

 mon. The optimum temperature of this bacterium is about 

 1 6 C. to 1 8 C., the maximum 28 C., and the minimum -2 C. 



Pathogenesis. E. F. Smith reports one disease of animals 

 which is due to a distinctly photogenic bacterium, and that 

 is the white or sluggish disease of sand fleas on the shores of 

 France and in the vicinity of Woods Hole, Massachusetts. 

 No diseases of plants have been reported as due to photogenic 

 bacteria. 



