Effect of Sulfanilamide on Electrode-Potential of Hemolytic Streptococcal Cultures

Abstract

Summary

1. Potentiometric measurements are reported of the electrode potentials of cultures of hemolytic streptococci growing in 25% horse-serum neopeptone-water with and without sulfanilamide. 2. The Eh of aërobic control cultures remained elevated until after active multiplication was well advanced, then rapidly fell about 50 mv. The Eh of aërobic sulfanilamide-cultures remained elevated much longer, but when bacteriostasis ceased, it also fell. 3. With a very large inoculum the Eh fell no more than with a small inoculum, but the change occurred many hours earlier. 4. The addition of cysteine or catalase, or the exclusion of air with vaseline not only lowered the potential of both control and sulfanilamide-cultures, but also definitely reduced the bacteriostatic effectiveness of sulfanilamide. 5. In the presence of 1% glucose, the Eh of both control and sulfanilamide-cultures remained elevated, and sulfanilamide was effective as a bacteriostatic agent. 6. Sulfanilamide bacteriostasis is accompanied by an elevated electrode potential; normal growth by a rapidly falling potential.