Inhibition of Growth and Respiration of Ophiobolus graminis var. avenae and Aspergillus niger by Cystine

Abstract

THE fungus Ophiobolus graminis infects the roots of wheat and barley, but does not infect oats. O. graminis var. avenae, however, infects oats as well. Both strains grow well in a simple medium containing potassium dihydrogen phosphate, sodium hydrogen phosphate, magnesium sulphate, glucose, thiamin, biotin, and a nitrogen source, usually ammonium nitrate or sulphate, or amino-acids. Most of the amino-acids give good growth when used singly as sole nitrogen source. Growth of O. graminis is stimulated by cysteine and cystine added to the basic medium containing ammonium nitrate up to a concentration of 0.01 M. Without an inorganic nitrogen salt, growth is very good with 0.04 M cysteine. Growth of var. avenae is inhibited by cystine and cysteine at concentrations as low as 10⁻⁶ M and at no concentration is growth stimulated¹. Growth of Aspergillus niger is also inhibited by cystine and cysteine². Penicillium notatum has also been described as susceptible to inhibition of respiration by cystine³.