The Gas Ratio and Some Correlated Distinguishing Properties of Bacteria of the Genus Proteus

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Abstract
The gas ratio (CO2/H2) and certain other biochemical properties of 108 strains of Proteus cultures Avere detd. 66 were recently isolated from natural sources and 42 were laboratory stock cultures. The organisms were grown in methyl-red medium in hermetically sealed pyrex culture cells and the gases collected by means of an automatic Sprengel pump. CO2 was absorbed by KOH in a bubbling absorption pipette and the H2 measured by slow combustion in pure O2. The recently isolated cultures of Proteus formed 3 distinct groups based on the gas ratio. The average ratio for each group was: I = 6.28; II = 1.60; III=1.05. Correlating with the gas ratio in each group were the final pH of the 0.5% glucose medium used for gas production, growth in Koser''s citrate broth, and production of indole and acetylmethylcarbinol. Each of the old cultures of Proteus also gave a gas ratio characteristic of one of the 3 groups formed by the fresh cultures, although 38 of the 42 belonged to Group III. The 3 groups of old cultures tended to show the same correlations in the biochem. properties which correlated with the gas ratio in the fresh cultures. Proteus should be revised to contain 3 spp., viz.. P. vulgaris, P. mirabilis, and P. hydrophilus.