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Morphology and Growth of a Temperature-sensitive Mutant of Aspergillus nidulans which Forms Aseptate Mycelia at Non-permissive Temperatures
Abstract
A study was made of the morphology and growth of young mycelia of a temperature-sensitive mutant (sepA2) of Aspergillus nidulans. At 25 °C the mutant grew at the same rate as the parental strain, formed septa and branched normally. At 30 and 37 °C the mutant grew at about three-quarters of the rate of the parental strain and, unlike the parental strain, branched dichotomously. The mutant was aseptate at 37 °C, and at 30 °C produced fewer septa than the parental strain. No septal initials were detected in mutant mycelia grown at 37 °C. Aseptate mycelia of the mutant were grown at 37 °C and then transferred to 25 °C. After transfer to 25 °C, septa appeared parasynchronously throughout aseptate regions of the mycelium previously formed at 37 °C. The intercalary compartments formed in this manner had a mean length which was identical with those of intercalary compartments formed by the parental strain at 37 °C or the mutant at 25 °C. The lag between transfer of mutant mycelia from 37 to 25 °C and the first appearance of septa varied from 0·15 to 2·75 h; the maximum lag observed was similar to the organisms’s doubling time (2·37 h) at 25 °C.
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© Society for General Microbiology 1979