An analysis of the spontaneous mutation rate measurement in filamentous fungi

Mutations related to gene methG1 of Aspergillus nidulans were analyzed, in order to study a mathematical model for the determination of the mutation rate per nucleus per generation, in filamentous fungi. A replica plating technique was used to inoculate, in a single operation, 26 colonies of the strain, into Petri dishes containing culture medium, and the nine central colonies were analyzed for size and number of conidia in each colony. Using this technique, several central colonies were analyzed with regard to the appearance of mutation, and the number and type of reversions were determined for each colony. The frequencies obtained for each reversion were analyzed, in order to verify if their distribution was in accordance with that of Greenwood and Yule. The data obtained allowed us to conclude that, using the mathematical model studied, it is possible to determine the mutation rate per nucleus, per generation, in filamentous fungi

An investigation of the nuclei of hülle cells of Aspergillus nidulans

Certain species of fungi of the genus Aspergillus produce a type of cells around the cleistothecium that are called hülle cells. To facilitate the analysis of the formation of these cells, an Aspergillus nidulans strain with high hülle cell production was obtained. Hülle cells from this strain were allowed to grow on dialysis membranes, where it was possible to observe their nuclei. The material was fixed with Carnoy, hydrolyzed with HCl and stained with Giemsa. Several nuclei approximately equal in size to the nuclei of hyphae and conidia were observed during the phase of hülle cell formation. The formation of a macronucleus measuring approximately 3.1 mum was observed in mature hülle cells. To compare the DNA amount, hülle cells and conidia of the CH-89 strain were isolated and submitted to DNA extraction (Tuyl, 1977). The amount of DNA per cell was, on average, 17.2 times greater than the amount of DNA in the conidia