Abstract
Although many anaerobic bacteria decompose proteins and the products of protein hydrolysis, only a few species are known to be able to satisfy their energy requirements by the fermentation of single amino acids or other nitrogenous compounds. These species are Clostridium tetanomorphum and Cl. cochlearium 1 , 2 which ferment glutamic acid and Cl. acidi-urici and Cl. cylindrosporum 3 , 4 which ferment uric acid and some other purines. Possibly Cl. botulinum, 5 Cl. sporogenes, 6 and Cl. tetani 7 should also be included in this group since cell suspensions of all 3 species can decompose single amino acids anærobically. However, it is not yet certain that these decomposition reactions can satisfy the energy requirements for growth of these bacteria.
Recent work in this laboratory has resulted in the discovery of 2 additional obligately anærobic bacteria that derive energy by the fermentation of single amino acids. Both organisms undoubtedly represent new species.
The first organism is a spindle-shaped, spore-forming, motile, Gram-negative rod which ferments alanine, serine and threonine as well as lactate and pyruvate. Methionine, valine, cysteine and aspartate are also attacked but much more slowly. Other amino acids and carbohydrates are not fermented.
The fermentation products are very similar to those produced by the genus Propionibacterium since all C3 substrates give rise to propionic and acetic acids approximately in accordance with the following equations:
Threonine, however, gives butyric instead of propionic acid as the characteristic product:
The second organism is a Gram-negative coccus that ferments glycine readily. Very few other amino acids are attacked and none decomposed as rapidly as glycine. The organism may therefore prove useful for the identification and estimation of this amino acid.
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