Abstract
It has been shown that Phytophthora infestans uses the nitrogen-containing fraction as its main source of energy, especially the amino-acid of the host tissues, and can not grow on a synthetic medium unless thiamine is added.
However the optimum amount of thiamine varies with the amount of sugar in the medium and with other conditions.
The present experiments were carried out to study the nitrogen sources of Phytophthora infestans, using synthetic culture solutions containing thiamine hydrochloride. The results obtained may be summarized as follows:
1. Optimum concentration of thiamine hydrochloride for this fungus is about 1γ in 10ml of culture solution.
2. Nitrate is a good nitrogen source for this fungus. Ammonium salt is not good, probably because the fungus is not able to assimilate ammonium salt completely owing to the fall in pH of the medium which is resulted from the initial uptake of ammonia.
This fungus can not assimilate nitrite.
3. The various amino-acids and amides differ in value from each other as nitrogen source for this fungus.
Asparagine, l-aspartic acid, l-glutamic acid, l-arginine monohydrochloride are utilized more efficiently than nitrate.
The worth of glutamine, l-phenyl alanine, l-proline as nitrogen source is inferior to that of nitrate and dl-valine, l-isoleucine, l-lysine, dl-tryptophan, l-methionine, l-cystine, glycine and l-leucine are found inadequate for a nitrogen source.
