Cyanuric acid as nitrogen source for micro-organisms

Summary Several fungi, among which species of Penicillium and Hormodendrum (?), were found to utilize cyanuric acid as a nitrogen source, assimilating 66 to 75% of its nitrogen in cell substance. The growth with cyanurate was essentially as good as with ammonia and urea nitrogen. The optimum reaction for growth was around pH 5 to 6, but pH 7 to 8 was suboptimal. No decrease in growth was seen at a cyanurate concentration of 9.3 mM. The triazine ring as such is thus not biologically very stable, and the strong persistance of the triazine herbicides simazine and atrazine must be ascribed to the external substituents and not to the central ring.