Unidentified Ninhydrin Positive Substance Found in the Culture Filtrate of Plant Pathogenic Fungi when Cultured on the Medium Containing Authentic Amino Acids (2)

Abstract

In the previous paper¹⁾ it was reported that a ninhydrin-positive substance (NPS) is produced in a modified Czapek's medium, in which NaNO₃ was replaced by an amino acid, inoculated with several plant pathogenic fungi. NPS is produced non-biologically in the modified Czapek-tryptophan medium when the medium was adjusted at pH 2.8 or 4.8, whereas it was not produced non-biologically at higher hydrogen-ion concentrations, 7.0, 9.0 and 11.0. NPS was produced in the same medium even at high hydrogen-ion concentrations, 6.8, 7.2, 8.2 and 9.0, when inoculated with plant pathogenic fungi such as Alternaria kikuchiana, Cladosporium herbarum and Colletotrichum dematium. In order to check the non-biological production of NPS at the acidic micro-environments distributed locally on the mycelial surface in liquid medium, silica gel particles were added, in place of fungal mycelium, to the medium and the production of NPS was tested, however, no NPS was detected. These results indicate that NPS is produced by the fungi through some metabolic process. NPS is produced in the medium within two days, reaching its maximum about 6th day after inoculation, at a wide pH range, from 6.8 to 9.0. In order to identify NPS, its behavior on thin layer chromatography was compared with those of artificially synthesized N-glycosides. The result indicated that NPS contains fructose as sugar moiety.