Which UV-irradiation, KX812(ac-) and KX814(nic-) were isolated, which require the acetate and nicotinamide for normal growth, respectively. Both mutants were able to grow somewhat on the minimal medium upto 10 days and eventually degenerated. Tetrad analysis showed linkage of ac- to the linkage group XIII and nic- to the linkage group VI. The gene ac- has been assigned to the region between 33.1 and 34.4 beyond nic- 15 on the left arm of the chromosome XIII. The position of nic- has been mapped between 22.6 and 23.0 on the right arm of the chromosome VI.