Vol. XXIV, pp. 179-184 June 16, 1911 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



SOME OBSERVATIONS ON A PHOTOGENIC MICRO- 

 ORGANISM, PSEUOOMONAS LUCIFER A 

 MOLISCH. 



BY F. ALEX. McDERMOTT, 



[Hygienic Laboratory, U.S. Public Health and Marine-Hospital Service. 



Washington, D.C.] 



Some years ago Dr. R. E. B. McKenney published in the 

 Proceedings of the Biological Society a very interesting paper 

 on luminous bacteria (Proc. Biol. Soc. Wash., 1902, Vol. 15, 

 pp. 213-231). The form which serves as the basis for what is 

 to follow has been isolated since Dr. McKenney's paper was 

 published, and appears to present some points of possible 

 interest. This organism is Pseudomonas lucifera Molisch, iso- 

 lated by Prof. Hans Molisch, of the Plant Physiology Institute 

 of the University of Vienna, and it is through the courtesy of 

 Professor Molisch that the parent culture for this work was 

 obtained. The organism was isolated from sea-water, and is 

 claimed by the discoverer to give the brightest light of any bac- 

 terial form so far isolated. 



Like most other luminous micro-organisms, Ps. lucifera will 

 grow on the ordinary culture media, under aerobic conditions, 

 but for luminescence there must be present 2.5 to 3.0 per cent 

 of sodium chloride, or some one of certain other mineral salts. 

 The use of media made from fish-meat is unnecessary. The light 

 given by ordinary bouillon-gelatin-salt cultures is a soft and beau- 

 tiful green, which after the eyes become accustomed to it, appears 

 of considerable intensity. A veritable " living lamp,'' as Dubois 

 has called it, may be made by coating the inside of a sterile 

 flask with the bouillon-gelatin-salt medium, and then inoculating 

 the surface of the gelatin with a liquid culture. Such a lamp 

 will continue to give light for about a week, though the light 



32— Proc. Hior . Soc. Wash., Vol. XXIV, 1911. (179) 



