Studies upon the methane fermentation. IV. The isolation and culture ofMethanobacterium Omelianskii

Summary

• 1. The isolation of pure cultures ofMb. Omelianskii has been achieved by the agar shake culture method. The purity of the cultures was established by microscopic examination and by testing for possible contaminants in suitable media under both aerobic and anaerobic conditions.

• 2. The organism is a thin, unbranched, Gram-variable rod. Motility occurs but is rare. Spores of low heat resistance are formed.

• 3. Growth of the organism in pure culture is shown to be influenced by a number of factors including hydrogen sulfide concentration, pH, phosphate and carbonate concentrations. The pH range of growth is from 6.5 to 8.1, the optimum being at 7.0–7.2. Increasing the phosphate concentration up to about 2% is beneficial because it increases the buffering of the medium. Growth and alcohol oxidation are directly proportional to the carbonate supply at low concentrations. High concentrations of soluble carbonates are inhibitory.

• 4. Mb. Omelianskii uses ammonia as a nitrogen source and is not stimulated by organic nitrogen compounds or growth factors such as are present in yeast extract.

• 5. A culture medium is described which allows rapid and abundant development ofMb. Omelianskii quite comparable with that obtainable with other obligately anaerobic bacteria.