FIVE FIGURES
Sodium azide is a poison known to be irritating to the human skin, but its main interest in biolo,gy is its interference with the respiration of cells. The inhibitory effect which it has on respiration is thought to be like that of cyanide but more specific (Armstrong and Fisher, '40). For this reason azide is useful in studies on respiratory mechanisms (e.g., Winzler, '40). Studies of the effects of azide on various bacteria have been made by Lichstein and Soule ('44), but they did not include any luminous bacteria among their experimental forms. Yet such bacteria offer an advantage in that one can study the effects of azide not only on the gross respiration but also on one of the respiratory chains which results in luminescence. The following report records such a study upon the respiration, luminescence and growth of a species of luminous bacteria, Achromobacter Fischeri.
Methods
Petri dish cultures of the bacteria grown for 24 hours at 25ยฐC. in the manner previously described (Giese, '41, '43) were washed three times and suspended in 31,' s Sorensen buffers at pH 6.9-7.1 containing enough NaCl to make a total salt concentration of 3%. The density of the bacteria, set each time to about the same value with a densimeter, was approximately 5 X 10 bacteria per cubic centimeter. When the concentration of bacteria was 2, 1, &, and 4 of the standard suspension the respiration per vessel per hour was 268,125,60 and 32
Considering the errors of dilution and of pipetting this is fairly close agreement and shows that the respiration is proportional to the concentration Some preliminary studies on effects of azide on respiration of luminous bacteria were made at Woods Hole, Massachusetts in 1940 (Fisher, K., and A. C . Giese, unpublished). It was found that addition of peptone to glucose greatly increased the rate of respiration. Since peptone is necessary for growth this excess respiration was thought to correspond to the activity metabolism such as is found in sea urchin eggs (Fisher, Henry and Low, '44). No evidence for such activity metabolism was found in tlie luminous bacteria.