This investigation studies effects of environmental factors on growth and carotenogenesis in Corynebacterium strain 7ElC. Changes in pH were found to effect growth more than carotenogenesis. However, certain nutrients or long incubation periods stimulated carotenoid formation more than growth. Dark conditions in a mineral salts-glucose medium stimulated growth, but minimized carotenogenesis. Tryptic soy broth or yeast extract elicited carotenogenesis in darkness. Although brief light exposure during inoculation was photoinductive, continuous exposure to light following inoculation was required for maximum pigment synthesis. Dark grown stationary phase cells required 24-hours of light for maximum pigment synthesis. Chloramphenicol inhibition of carotenogenesis in dark grown cells exposed to light showed that enzymes needed for carotenoid synthesis were absent from dark grown cultures.

Studies were evaluated on the effects of known growth factors on the growth and carotenogenesis of Corynebacterium species strain 7ElC. The complex medium, Tryptic Soy Broth,was found to stimulate growth and production of more pigment in the light and in the dark than did a mineral salts-glucose medium. A complete amino acid mixture added to LSG enhanced carotenogenesis in the dark in Corynebacterium 7ElC, while B-vitamins retarded carotenogenesis. No absolute requirement for one or more amino acids was found,indicating a multiple amino acid requirement. The fewest amino acids found to stimulate carotenogenesis in the dark were a combination of those in the Serine and Histidine families which include serine, glycine, cysteine, and histidine.

The effects of light, light "mimicking" chemicals, and protein synthesis inhibitors on the photo-induced carotenogenesis of Corynebacterium 7EIC were studied. Changes in the dosage of fluorescent light applied to dark grown cells showed a dose related carotenogenic response. Maintaining the same dosage but varying the wavelength of monochromatic light revealed that light with a wavelength of 280 to 450nm was responsible for photo-induction. It further showed a peak of photo-induction between the wavelengths of 370 and 430nm. The light "mimicking" chemicals antimycin A and p-Chloromercurybenzoate were shown to have no light "mimicking" effects. The transcriptional inhibitor of protein synthesis actinomycin D partially inhibited, and chloramphenicol a translational inhibitor, completely inhibited photo-induced carotenogenesis.