Abstract
Luminescence intensity is inhibited at once on addition of sulfanilamide either to broth cultures, or washed cell suspensions of luminous bacteria in phosphate buffered NaCl solutions containing glucose as oxidizable substrate. At the respective optimum temperatures of marine species, Achromobacter Fischeri (25 to 28°C), Photobacterium phosphoreum (15 to 17°C), and a fresh-water species, Vibrio phosphorescens (28 to 30° C), a concentration of 100 mg % sulfanilamide greatly reduces the intensity of luminescence, with little or no effect on the rate of respiration (Fig. 1). Except at high concentrations of the drug the inhibition of luminescence is largely or completely reversible (Table I) by centrifuging and resuspending the cells in a drug-free solution. In all these respects the effects of sulfanilamide resemble those of typical narcotics, such as the urethanes 1 , 2 and barbital. 3 By analogy, it would be predicted that sulfanilamide will inhibit the luminescent oxidation of purified Cypridina luciferin and luciferase in vitro. 4
Growth of luminous bacteria in nutrient broth is prevented by high concentrations of sulfanilamide (500 mg %), while lower concentrations retard growth and sometimes allow the development of cultures which do not luminesce. In sub-cultures of the latter, luminescence reappears, showing that no permanent change in the characteristics of the organism has taken place.
Concentrations of sulfanilamide which reduce luminescence intensity to as little as 10% cause neither an appreciable bactericidal effect, nor a reduction in number of luminous colonies in the plate count (Table II).
Para-aminobenzoic acid 5 at high concentrations (50 mg %) inhibits growth and luminescence, but exerts anti-sulfanilamide effects on broth cultures at much lower concentrations. Para-aminobenzoic acid does not, however, have any appreciable effect on the sulfanilamide inhibition of luminescence in mature cultures or washed cell suspensions, over a range of 0.001 to less than 0.0000001 M.
Get full access to this article
View all access options for this article.