Effect of Sodiummonoiodoacetate upon Metabolism of Streptobacterium casei

Abstract

Present evidence indicates that sodiummonoiodoacetate is a fairly specific inhibitor of the lactic acid cycle in frog's muscle and in many other tissues. 1 However, the electrical, mechanical, and thermal aspects of the first few contractions of poisoned muscle differ little if at all from those of unpoisoned muscle, indicating that in this instance the Meyerhof cycle can be temporarily replaced by other mechanisms.

The authors studied the effect of this substance upon an organism in which lactic acid formation is practically the whole metabolic story. Streptobacterium casei was chosen, 2 , 3 a pure culture of which was kindly furnished by Dr. C. B. van Niel of the Hopkins Marine Station.

The bacteria were grown on agar plates, 0.2% glucose and containing CaCO₃. Mass cultures so prepared were scraped from the agar and suspended in sterile solutions of 0.2% glucose, 0,3% sodium bicarbonate. Lactic acid production was measured in the usual way, using Warburg respirometers in a thermostat at 21.5°C. 4 The sodiummonoiodoacetate was placed in the bulb or “pear” of the manometer vessel, and added to the suspension about an hour after the beginning of the experiment, so that each preparation furnished its own control. Blank determinations were also run, and proper corrections made.

Briefly, it was found that concentratioix of sotliummonoiodoacetate in the respirometer vessels of up to 0.008% had little effect upon the rate or extent of lactic acitl procluction, while at a concentration of 0.08% a change in slope was noted 65 minutes after the adddtion of the reagent, and at a concentration of 0.16% such change in slope developed 35 minutes after addition. Both the rate and final aniount of lactic acitl formetl tlecreaced as the concentration of sodiummonoiodoacetate was raised.