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Updated: Jul 11, 2025
Quantitative Analysis of Aspergillus nidulans Growth Rate using Live Microscopy and Open-Source Software
Published on: July 24, 2021
Gamma-irradiated Aspergillus conidia show a growth curve with a reproductive death phase
Shigetoshi Horikiri1,2, Mami Harada1, Ryoko Asada2,3,4
1Department of Quantum and Radiation Engineering, Graduate School of Engineering, Osaka Prefecture University , 1-2 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531, Japan.
Abstract:
In this study, we evaluated the effects of gamma irradiation on the germination of Aspergillus conidia and mycelial growth using microscopy and predictive microbiological modeling methods. A dose of 0.4 kGy reduced the germination rate by 20% compared to the untreated control, indicating interphase death due to the high radiation dose. The number of colonies formed (5.5%) was lower than the germination rate (69%), suggesting that most colonies died after germination. Microscopic observations revealed that mycelial elongation ceased completely in the middle of the growth phase, indicating reproductive death. The growth curves of irradiated conidia exhibited a delayed change in the growth pattern, and a decrease in slope during the early stages of germination and growth at low densities. A modified logistic model, which is a general purpose growth model that allows for the evaluation of subpopulations, was used to fit the experimental growth curves. Dose-dependent waveform changes may reflect the dynamics of the subpopulations during germination and growth. These methods revealed the occurrence of two cell death populations resulting from gamma irradiation of fungal conidia and contribute to the understanding of irradiation-induced cell death in fungi.
Insights
Gamma irradiation significantly impacts Aspergillus conidia germination and fungal growth. High doses cause interphase and reproductive death, revealing two distinct cell death populations after irradiation.
Area of Science:
- Mycology
- Radiation Biology
- Microbiology
Background:
- Gamma irradiation is explored for its effects on fungal viability.
- Understanding irradiation-induced cell death in fungi is crucial for food safety and sterilization applications.
Purpose of the Study:
- To evaluate the impact of gamma irradiation on Aspergillus conidia germination and mycelial growth.
- To investigate the mechanisms of radiation-induced fungal cell death using microscopy and predictive modeling.
Main Methods:
- Microscopy was used to observe conidia germination and mycelial development.
- Predictive microbiological modeling, specifically a modified logistic model, was employed to analyze growth curves.
- Dose-dependent effects of gamma irradiation were assessed.
Main Results:
- A dose of 0.4 kGy reduced germination by 20%, indicating interphase death.
- A significant drop from germination rate to colony formation suggests post-germination death.
- Microscopic analysis showed complete cessation of mycelial elongation, indicative of reproductive death.
- Growth curves displayed delayed patterns and reduced slopes in irradiated conidia, with dose-dependent waveform changes.
Conclusions:
- Gamma irradiation induces distinct cell death populations in fungal conidia.
- The study elucidates mechanisms of irradiation-induced cell death in fungi, contributing to microbiological safety knowledge.
