Co- operative effects of hydrogen peroxide and iodine on yeast species. (a) The enhancement in the inhibition of yeast growth by hydrogen peroxide and iodine used in the mixture. Six serial dilutions of each culture were plated in each horizontal row, with most concentrated suspensions on the left. (b) Enhanced incidence of small colonies in yeast cells treated with hydrogen peroxide and with the mixture iodine-hydrogen peroxide. Stars indicate significantly different values (P < 0.05).