Zinc Effects on Growth and Cynodontin Production of Helminthosporium Cynodontis

SUMMARY

By strain selection, a culture of Helminthosporium cynodontis Marignoni has been isolated which grows rapidly in shaken-submerged cultures and which can produce the pigment, cynodontin, in yields up to one-fifth of the dry weight of the mycelium after 5 days in culture. This strain requires trace quantities of zinc. As zinc concentrations are increased in the range 0.3 to 3.0 μM, increased growth occurs concomitant with increased uptake of glucose and phosphate and a rise in the pH of the medium. Optimum zinc concentrations for growth result in a marked reduction of cynodontin formation during a 5-day period within which a relatively high yield of pigment can otherwise be obtained.