Previous investigations of the metabolism of viruses have been hindered by the difficulty or impossibility of securing adequate amounts of the active agents in a pure state. However, by the application of recently developed technics, it is possible to prepare large quantities of vaccine virus free from living host cells, and to concentrate the suspensions to any desired degree. Advantage has been taken of this in the present investigation. Large quantities of washed elementary bodies of vaccinia were prepared, and suspended in small volumes of liquid. The amounts of oxygen consumed aerobically and of acid produced anaerobically were measured, the latter as carbon dioxide released from a buffer solution containing sodium bicarbonate and carbon dioxide. Even when large amounts of virus were used (as much as 26 mg., dry weight, of elementary bodies) the quantities of oxygen consumed and of acid liberated were very small. Furthermore, the greater part of the gaseous exchange which occurred took place in the first hour of observation; during the succeeding periods no absorption of oxygen or liberation of carbon dioxide was demonstrated. No increased absorption followed the addition of glucose, glucose monophosphate, or methylene blue. At the conclusion of the experiments the virus was shown to be fully active. Such findings are in sharp contrast to the results to be expected if true respiration were taking place, as for example in resting bacteria, in which case the quantities of oxygen consumed are much greater and are relatively constant during the period of observation.
It was considered that the failure of elementary bodies to consume oxygen might be due to lack of a proper substrate, or of respiratory supplements. In an effort to supply these essentials, a tissue extract was prepared which was shown to contain respiratory supplements, and this was added to the suspension of elementary bodies. It had, however, no effect on the rate of utilization of oxygen by the elementary bodies.
Since elementary bodies alone, and in the presence of simple and complex substrates, showed no evidence of continued respiration, it was decided to ascertain whether they contained substances capable of stimulating the metabolism of other cells. Rabbit erythrocytes were used for this purpose; and the amounts of oxygen consumed under aerobic conditions and of acid produced under anaerobic conditions, respectively, by the red blood cells were determined. In neither case was any consistent stimulation of metabolism demonstrated.
In the interpretation of the results of our experiments it must be borne in mind that the conditions under which they were performed are highly artificial, and while they are compatible with the survival of virus, there is no reason to suppose that they would permit its growth (3, 4). It may be said, however, that under the conditions which have been described above, no evidence was secured that vaccine virus, in considerable amounts, freed from viable host cells and bacteria, is capable of continued utilization of measurable quantities of oxygen, or of continued release of appreciable amounts of acid.