[Studies of Nocardia pellegrino SN 5108 pigment mutants: reasons for differences in pigmentation (author's transl)].

Yellow and white mutants of the strains Nocardia pellegrino SN 5108 R have been isolated. Regarding their morphological and physiological properties, the mutants are identical with the wild type bacteria with the exception of their pigmentation and lipid composition. However, the pigment composition (number, Rf-values and spectra of the pigment components) of the yellow mutant is identical with that of the wild type; as a consequence, the modified pigmentation of the yellow mutant cannot be explained by an altered pigment synthesis. The wild type cells and the mutant SN 5108 G contain three main pigment components designated as I, II and III. Components II and III posses a marked indicator character and show a bathochromic shift in solutions of pH 12 or higher. Components II and III contain functional groups which are able to react with acetic acid yielding acetylated products; after acetylating, no bathochromic shift in alkali occurs. Intact cells of the wild type retain their orange-red pigmentation in buffer solution with a pH-value of 12 or higher. Cells of the yellow mutant, however, change the yellow color immediately after the alkali treatment to orange-red; this new color is identical with that of the wild type and can be changed to yellow by placing the cells into 1 N HCl. Regarding these facts it seems to be very probable that the functional groups of the pigment components II and III are differently bound in the wild type and mutant cells. In the mutant, they are accessible to OH- ions yielding a bathochromic shift while in the wild type cells, OH- ions are unable to provoke this shift. It seems to be also probable that different lipids in the two strains are responsible for the binding of the pigments. So far known, this is the first observation about the occurence of pigment mutants with an altered pigment binding site in the cells.