Cochliobolus sativus. II. Photoactivated Pigmentation

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Abstract
An unidentified pigment was extracted with organic solvents from the mycelium of isolates of Cochliobolus sativus. The pigment was produced in young actively growing cultures. Nutrition greatly influenced both growth and pigment production but not in proportionate amounts. Media containing glucose and N as nitrate, alanine, l-asparagine, l-argenine, glycine, or l-proline appeared most conducive to both growth and pigmentation. The pigment was a pH indicator with an end-point about 8.6, above and below which it was blue and pink, respectively. Light of wave lengths between 390 and 513 mu stimulated the production of color. Photo-activation, however, was an oxidative process, since illumination in the absence of O2 failed to promote pigment formation. The inhibition of pigmentation by potassium cyanide and sodium azide suggested that the process was mediated by terminal oxidases. Other Helminthosporium spp. produced pigments which were similar in absorption spectra to that found in C. sativus. Color formation in several species, however, occurred regardless of light condition.