ACENAPHTHENE‐REQUIRING STRAINS OF PENICILLIUM CHRYSOGENUM

Abstract

EARLY IN THE course of a program of research dealing with induced and natural variation in Penicillium notatum Westling and P. chrysogenum Thom (Backus and Stauffer, 1955) several chemical compounds were used in an attempt to obtain mutants. Some of the most interesting results were obtained by treating young plate cultures of P. notatum strain NRRL-832 with acenaphthene. Petri-dish plates of honey-peptone agar were inoculated with the fungus at the edge of the dish and, when a small colony had developed, acenaphthene crystals were piled up in a semicircle about the mycelial growth, perhaps a centimeter from its margin. The chemical appeared to be highly inhibitory to the fungus inasmuch as radial spread of the colony was almost completely arrested at first and little or no production of conidia occurred. Upon further incubation, however, rapidly-advancing sectors appeared which grew out over and through the acenaphthene barrier, sporulating profusely even in direct contact with the crystals. Conidia or hyphal tips froin these sectors transferred to tube slants of ordinary honeypeptone agar yielded cultures abnormal in appearance, but good mycelial development and heavy sporulation were obtained when similar transfers were made to slants of honey-peptone agar saturated with acenaphthene. Thus it appeared that acenaphthene-requiring variants of P. notatum had been secured. Additional experiments employing acenaphthene as a mutagenic agent and further studies on the behavior of acenaphthene-requiring strains are reported here. Considerable information is available concerning the biological effects of acenaphthene. This substance has been demonstrated to have an effect on mitosis similar to that of colchicine (Kostoff, 1938a), and it has been successfully employed to induce polyploidy in higher plants (Shmuck, 1938; Kostoff, 1938b; Fatalizade, 1939) and in yeast (Subramaniam and Murthy, 1949) . Acenaphthene or acenaphthene vapors have been shown to inhibit the growth and reproduction of a variety of fungi, although marked differences in the relative susceptibility of various species have been reported (Bateman and Henningsen, 1923; McDavid and Daniels, 1951). Similar differences in reaction to the chemical were noted in some recent tests in the University of Wisconsin mycological laboratories, where the citrus fruit-rotting penicillia were found tobe relatively tolerant while Aspergillus amstelodami proved to be strongly affected (James Grosk-