A SIMPLIFIED MEDIUM FOR GROWTH AND SPORULATION OF PILOBOLUS SPECIES

Formation of sporangia induced by light in Pilobolus species has been reported by several workers (1, 4, 6, 9, 12, 13, 14). Since 1952 synthetic media containing specific growth factors: hemin (8, 10, 11), coprogen (2, 3, 15), or ferrichrome (7, 9) have been used for culturing members of this genus. Because Pilobolus can be grown on synthetic media and sporangium formation is induced with light, this genus has been suggested for use in studying problems dealing with sporangium development (9). The present research deals with the study of various synthetic media to determine which would be best suited for sporangium development. In the initial experiments (5) a strain of Pilobolus kleinii van Tiegham was separately incubated on various media described in the literature. Best results were obtained using a solid hemin-asparagine medium described by Page (11). Although good vegetative growth resulted and numerous trophocysts were formed, sporangia were seldom observed. Changes in the pH, light regime, and culturing conditions with Page's medium and modification of the other synthetic media failed to provide cultures which regularly produced sporangia (5). After numerous experiments using the constituents of Page's medium, coprogen medium, ferrichrome medium, as well as many other compounds used in various concentrations and combinations, a simplified hemin medium was developed (5). In contrast to other media, cultures on this new medium were slightly more vigorous, had more densely pigmented vegetative growth, and produced abundant sporangia. Page's hemin-asparagine medium (PM) was prepared as described (11) except that the concentration of (NH4)2S04 was decreased from 1.32 g/l to 0.66 g/l and the concentration of MgS04-7H20 was decreased from 1.0 g/l to 0.5 g/l. These changes improved the rate and density of vegetative growth but did not improve the extremely sparse 1254