INVOLVEMENT OF ENDOGENOUS PORPHYRINS IN THE INACTIVATION OF CANDIDA-GUILLIERMONDII BY VISIBLE-LIGHT

Biosynthesis of endogenous porphyrins and the photosensitized inactiva tion of the yeast Candida guilliermondii grown in the presence of the porphyrin precursor 5-aminolevulinic acid were studied. 5-Aminolevulin ic acid induced the accumulation in the yeast cells of mainly metallop orphyrins, which displayed no photosensitizing activity and did not af fect cell sensitivity to visible light (400-600 nm). When 2,2'-dipyrid yl, a compound that forms complexes with a number of metal ions, was a dded to the cultivation medium in combination with 5-aminolevulinic ac id, the photosensitivity of the yeast cells significantly increased du e to the increase in the content of free photodynamically active porph yrin compounds, primarily protoporphyrin IX.