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)
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