Physicochemical factors influencing growth and pigment synthesis by Micrococcus roseus.

Abstract

Growth of and carotenoid synthesis by Micrococcus roseus are optimum at pH 6.8 and pH 7.5 in a defined medium. Maximum growth and pigment content were obtained in aerobic cultures at 25 C. Supplementing the medium with more than 0.2% NaCl resulted in less growth and decreased pigment content per unit mass of cells. At pH 7.5 the absence of visible light had no effect on growth or pigment content, but at pH 6.8 both were decreased in dark-grown cultures. Biotin did not reverse inhibition of growth in the dark. Dark inhibition was reversed by exposure of lag or early log phase cultures to visible light for 30 min, but late log or stationary phase cultures grown in the dark did not respond. Stationary phase dark-grown cultures resumed growth and pigment synthesis during a 24-h period in light. Serial culture in the dark did not result in a further decrease in growth or pigment synthesis; and when cells from serial cultures grown in darkness were used as inoculum for cultures grown in the light, maximum growth and pigment synthesis occurred. These data suggest that light is required for induction of maximum growth and pigment synthesis. A crude action spectrum was determined and suggests that light in the range from 625 to 700 mμ may be responsible for photoinduction.None of the environmental variations altered the absorption spectrum of pigment extracts. Conditions which were optimum for growth were also optimum for pigment synthesis.