Deoxyribonuclease release by incompatible strains of Proteus

Using incompatible strains of Proteus growing on the same deoxyribonuclease (DNase) agar plate, it was found that DNase is consistently released at the demarcation line. DNase was shown to be released when the swarming organisms were killed. While screening Enterobacteriaceae according to the method of Schreier (1969) on agar containing deoxyribonucleic acid (DNA), it was noticed that when dissimilar strains of Proteus met, there was a breakdown of DNA. Schreier (1969) reported that, of the Enterobacteriaceae, only Serratia sp. consistently release DNase, while 10% of Proteus sp. and Pseudomonas sp. release DNase, but in much smaller amounts. Dienes (1946) reported that when dissimilar strains of Proteus are allowed to swarm on the same agar plate, a demarcation line the organisms show various degenerative changes. Many organisms at the line have been shown to be nonviable. When identical strains of Proteus are used, no line is produced. The present study reports DNase release at the demarcation (Dienes) line, questions the significance of this, and suggests the usefulness of the phenomenon in the Dienes typing of Proteus sp.