Studies on Capsule Formation: III. Inhibition of Capsule Formation of Klebsiella pneumoniae (Friedländer's Bacterium) by an Agent Produced by a Soil Bacillus.

The conditions under which Klebsiella pneumoniae forms its largest capsules were reported in an earlier publication (Hoogerheide, 1939). The underlying principle of that study was the hypothesis that capsular polysaccharide synthesis is brought about by the action of an enzyme system in the cell, the activity of which can be studied in the same way as that of other metabolic enzyme systems. In a second paper (Hoogerheide, 1940) the influence of electrolytes on this enzyme system was studied, and it was found that electrolytes, when added to the culture medium, bring about a marked inhibition in the production of capsular polysaccharide. While engaged in attempts to isolate from bacterial sources possible enzymes capable of hydrolyzing the capsular substance of Friedlander's bacterium (similar to the enzymes described by Dubos and Avery (1931) and by Sickles and Shaw (1934, 1935), which digest the polysaccharides of Pneumococcus types I, II, III and VIII), we isolated several strains of a bacillus which appeared to have the remarkable property of excreting a soluble agent. By means of this agent, the bacillus is able to prevent Friedlander's bacterium from forming capsules. The present paper describes the isolation of this soil bacillus and the preparation of extracts containing the active principle.